Accessing value of a Variable in parent from custom control

microsoft.public.dotnet.framework

13 Nov 2006 12:08 PM

Zahid Hayat

Is it possible to access value of a variable in Parent Form within control at
runtime?
Please provide an example (possibly in VB).

13 Nov 2006 1:26 PM

Ciaran O''Donnell

It isnt very object oriented as the control isnt part of the form and could
be used on a form without that variable. Unless the controls code definition
was inside the forms, in which case it would be a able to access privates
after casting the Parent property to the type of the parent form.

Ciaran O'Donnell

Show quote

"Zahid Hayat" wrote:

> Is it possible to access value of a variable in Parent Form within control at
> runtime?
> Please provide an example (possibly in VB).

13 Nov 2006 4:32 PM

Dale

You can create a property in the control and then, when the parent form
initializes the control or changes the value of the variable, set the value
of the property in the control.

Though, like Ciaran says, it is not very object oriented, I have had cases
where I had to pass the parent form as a property to a control. To get
around the issue he identifies of the control being used in a different form,
then you create an interface for the data that the control requires from its
parent and implement that interface in all parents that use that control. In
that way, by casting to the interface type, you can make any form that uses
your control into something you can use inside your control.

HTH

Dale

--
Dale Preston
MCAD C#
MCSE, MCDBA

Show quote

"Zahid Hayat" wrote:

> Is it possible to access value of a variable in Parent Form within control at
> runtime?
> Please provide an example (possibly in VB).

14 Nov 2006 11:17 AM

Zahid Hayat

First I would like to thank both of you for replying to my question. As I do
not have any experience with interfaces, therefore if you can provide an
example I will be greatfull.

Zahid.

Show quote

"Dale" wrote:

> You can create a property in the control and then, when the parent form
> initializes the control or changes the value of the variable, set the value
> of the property in the control.
>
> Though, like Ciaran says, it is not very object oriented, I have had cases
> where I had to pass the parent form as a property to a control. To get
> around the issue he identifies of the control being used in a different form,
> then you create an interface for the data that the control requires from its
> parent and implement that interface in all parents that use that control. In
> that way, by casting to the interface type, you can make any form that uses
> your control into something you can use inside your control.
>
> HTH
>
> Dale
> --
> Dale Preston
> MCAD C#
> MCSE, MCDBA
>
>
> "Zahid Hayat" wrote:
>
> > Is it possible to access value of a variable in Parent Form within control at
> > runtime?
> > Please provide an example (possibly in VB).

14 Nov 2006 2:23 PM

Dale

Unfortunately, I am not a VB.Net developer but you should hopefully be able
to figure this out from the C#.

Let's say that your control is MyControl and your form is MyForm. The
instance, in my example, of MyControl is named myControl. Assume your form
needs a string variable we'll call formString and an int variable we'll call
formInt that are defined in the parent form. Create an interface called, for
instance, iUsesMyControl.

In your form class declaration, change
     public class MyForm : Form

to
     public class MyForm : Form, iUsesMyControl

I think the VB would look like
     Public Class MyForm : Extends iUsesMyControl

Your interface, iUsesMyControl, would look like:
     internal interface iUsesMyControl
     {
          int FormInt { get; set; }
          string FormString { get; set; }
     }

Basically, we're defining two properties in the interface that all classes
implementing iUsesMyControl must implement. Check your VB documentation for
how to define properties in an interface in VB.

Your implementation of iUsesMyControl in your form would look like

     private int formInt; // though this may have been previously defined
elsewhere.
     internal int FormInt
     {
          get { return formInt; }
          set { formInt = value; }
     }

     private string formString;
     internal string FormString
     {
          get { return formString; }
          st { formString = value; }
     }

Check your VB documentation for how to define the variables and expose them
as properties in VB to accomplish the above C# code in VB.

In your control, add a property:

     private iUsesMyControl parentForm;
     internal iUsesMyControl ParentForm
     {
          set { parentForm = value; }
     }

Somewhere early in your parent form, perhaps the load event, add
     myControl.ParentForm = (iUsesMyControl)this;

This passes the MyForm to MyControl but by casting to iUsesMyControl it
tells MyControl only about the two variables defined in iUsesMyControl. I
think this, in VB would be:
     myControl.ParentForm = CType(Me, iUsesMyControl)

Now, in your control, you have available:
     parentForm.FormInt
and
     parentForm.FormString

--
Dale Preston
MCAD C#
MCSE, MCDBA

Show quote

"Zahid Hayat" wrote:

> First I would like to thank both of you for replying to my question. As I do
> not have any experience with interfaces, therefore if you can provide an
> example I will be greatfull.
>
> Zahid.
>
>
>
> "Dale" wrote:
>
> > You can create a property in the control and then, when the parent form
> > initializes the control or changes the value of the variable, set the value
> > of the property in the control.
> >
> > Though, like Ciaran says, it is not very object oriented, I have had cases
> > where I had to pass the parent form as a property to a control. To get
> > around the issue he identifies of the control being used in a different form,
> > then you create an interface for the data that the control requires from its
> > parent and implement that interface in all parents that use that control. In
> > that way, by casting to the interface type, you can make any form that uses
> > your control into something you can use inside your control.
> >
> > HTH
> >
> > Dale
> > --
> > Dale Preston
> > MCAD C#
> > MCSE, MCDBA
> >
> >
> > "Zahid Hayat" wrote:
> >
> > > Is it possible to access value of a variable in Parent Form within control at
> > > runtime?
> > > Please provide an example (possibly in VB).

14 Nov 2006 5:24 PM

RobinS

I think this would be the VB code for that:

In your form, add an Implements for the interface, and add the properties.
You will want to have private variables to keep the current value,
you are exposing them through a property.

    public class MyFrom
        Implements iUsesMyControl

        Private _FormInt as Integer
        Public Property FormInt() As Integer Implements
IUsesMyControl.FormInt
            Get
                return _FormInt
            End Get
            Set(ByVal value As String)
                _FormInt = value
            End Set
        End Function
        Private _FormString as String
        Public Property FormString() As String Implements
IUsesMyControl.FormString
            Get
                return _FormString
            End Get
            Set(ByVal value As String)
                _FormString = value
            End Set
        End Function
        ....(other form code)
    End Class

Public Interface IUsesMyControl
    Property FormInt as Integer
    Property FormString as String
End Interface

In your control:
    '**I'm not sure about this; Either I have it wrong,
    '** or there's some way to define something as
    '** an interface. If this doesn't work, try
    '** "implements IUsesMyControl" instead of "as IUsesMyControl".
    Private _parentForm as IUsesMyControl
    Public Readonly Property ParentForm as IUsesMyControl
        Set
            _parentForm = value
        End Set
    End Property

Somewhere early in your parent form
    myControl.ParentForm = DirectCast(me, IUsesMyControl)

I think that's right; feel free to correct me if I got any of it wrong.
Robin S.
-------------------------
Show quote

"Dale" <dale0973@nospam.nospam> wrote in message
news:6AD37C2A-C539-45DB-BE10-E733ACEBC094@microsoft.com...
> Unfortunately, I am not a VB.Net developer but you should hopefully be
> able
> to figure this out from the C#.
>
> Let's say that your control is MyControl and your form is MyForm. The
> instance, in my example, of MyControl is named myControl. Assume your
> form
> needs a string variable we'll call formString and an int variable we'll
> call
> formInt that are defined in the parent form. Create an interface called,
> for
> instance, iUsesMyControl.
>
> In your form class declaration, change
>     public class MyForm : Form
>
> to
>     public class MyForm : Form, iUsesMyControl
>
> I think the VB would look like
>     Public Class MyForm : Extends iUsesMyControl
>
> Your interface, iUsesMyControl, would look like:
>     internal interface iUsesMyControl
>     {
>          int FormInt { get; set; }
>          string FormString { get; set; }
>     }
>
> Basically, we're defining two properties in the interface that all classes
> implementing iUsesMyControl must implement. Check your VB documentation
> for
> how to define properties in an interface in VB.
>
> Your implementation of iUsesMyControl in your form would look like
>
>     private int formInt; // though this may have been previously defined
> elsewhere.
>     internal int FormInt
>     {
>          get { return formInt; }
>          set { formInt = value; }
>     }
>
>     private string formString;
>     internal string FormString
>     {
>          get { return formString; }
>          st { formString = value; }
>     }
>
> Check your VB documentation for how to define the variables and expose
> them
> as properties in VB to accomplish the above C# code in VB.
>
> In your control, add a property:
>
>     private iUsesMyControl parentForm;
>     internal iUsesMyControl ParentForm
>     {
>          set { parentForm = value; }
>     }
>
> Somewhere early in your parent form, perhaps the load event, add
>     myControl.ParentForm = (iUsesMyControl)this;
>
> This passes the MyForm to MyControl but by casting to iUsesMyControl it
> tells MyControl only about the two variables defined in iUsesMyControl. I
> think this, in VB would be:
>     myControl.ParentForm = CType(Me, iUsesMyControl)
>
> Now, in your control, you have available:
>     parentForm.FormInt
> and
>     parentForm.FormString
>
>
> --
> Dale Preston
> MCAD C#
> MCSE, MCDBA
>
>
> "Zahid Hayat" wrote:
>
>> First I would like to thank both of you for replying to my question. As I
>> do
>> not have any experience with interfaces, therefore if you can provide an
>> example I will be greatfull.
>>
>> Zahid.
>>
>>
>>
>> "Dale" wrote:
>>
>> > You can create a property in the control and then, when the parent form
>> > initializes the control or changes the value of the variable, set the
>> > value
>> > of the property in the control.
>> >
>> > Though, like Ciaran says, it is not very object oriented, I have had
>> > cases
>> > where I had to pass the parent form as a property to a control. To get
>> > around the issue he identifies of the control being used in a different
>> > form,
>> > then you create an interface for the data that the control requires
>> > from its
>> > parent and implement that interface in all parents that use that
>> > control. In
>> > that way, by casting to the interface type, you can make any form that
>> > uses
>> > your control into something you can use inside your control.
>> >
>> > HTH
>> >
>> > Dale
>> > --
>> > Dale Preston
>> > MCAD C#
>> > MCSE, MCDBA
>> >
>> >
>> > "Zahid Hayat" wrote:
>> >
>> > > Is it possible to access value of a variable in Parent Form within
>> > > control at
>> > > runtime?
>> > > Please provide an example (possibly in VB).

18 Nov 2006 11:34 AM

Zahid Hayat

My parent Form looks like this:
=======================
Public Class Form1
    Implements iUsesMyControl
    Private _formInt As Integer
    Private _formString As String
    Public var1 As Integer
    Private mycontrol As ContainerControl

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load

        _formInt = 123
        _formString = "Zahid"
        mycontrol = DirectCast(Me, iUsesMyControl)

    End Sub

    Public Property FormInt() As Integer Implements iUsesMyControl.FormInt
        Get
            Return _formInt
        End Get
        Set(ByVal value As Integer)
            _formInt = value
        End Set
    End Property

    Public Property FormString() As String Implements
iUsesMyControl.FormString
        Get
            Return _formString
        End Get
        Set(ByVal value As String)
            _formString = value
        End Set
    End Property
End Class
============

I do not understand the implements of Control itself. Do we need to
implement another interface 'iUsesMyControl' as we did in the parent from
(Form1)?

Show quote

"RobinS" wrote:

> I think this would be the VB code for that:
>
> In your form, add an Implements for the interface, and add the properties.
> You will want to have private variables to keep the current value,
> you are exposing them through a property.
>
>     public class MyFrom
>         Implements iUsesMyControl
>
>         Private _FormInt as Integer
>         Public Property FormInt() As Integer Implements
> IUsesMyControl.FormInt
>             Get
>                 return _FormInt
>             End Get
>             Set(ByVal value As String)
>                 _FormInt = value
>             End Set
>         End Function
>         Private _FormString as String
>         Public Property FormString() As String Implements
> IUsesMyControl.FormString
>             Get
>                 return _FormString
>             End Get
>             Set(ByVal value As String)
>                 _FormString = value
>             End Set
>         End Function
>         ....(other form code)
>     End Class
>
> Public Interface IUsesMyControl
>     Property FormInt as Integer
>     Property FormString as String
> End Interface
>
> In your control:
>     '**I'm not sure about this; Either I have it wrong,
>     '** or there's some way to define something as
>     '** an interface. If this doesn't work, try
>     '** "implements IUsesMyControl" instead of "as IUsesMyControl".
>     Private _parentForm as IUsesMyControl
>     Public Readonly Property ParentForm as IUsesMyControl
>         Set
>             _parentForm = value
>         End Set
>     End Property
>
> Somewhere early in your parent form
>     myControl.ParentForm = DirectCast(me, IUsesMyControl)
>
> I think that's right; feel free to correct me if I got any of it wrong.
> Robin S.
> -------------------------
> "Dale" <dale0973@nospam.nospam> wrote in message
> news:6AD37C2A-C539-45DB-BE10-E733ACEBC094@microsoft.com...
> > Unfortunately, I am not a VB.Net developer but you should hopefully be
> > able
> > to figure this out from the C#.
> >
> > Let's say that your control is MyControl and your form is MyForm. The
> > instance, in my example, of MyControl is named myControl. Assume your
> > form
> > needs a string variable we'll call formString and an int variable we'll
> > call
> > formInt that are defined in the parent form. Create an interface called,
> > for
> > instance, iUsesMyControl.
> >
> > In your form class declaration, change
> >     public class MyForm : Form
> >
> > to
> >     public class MyForm : Form, iUsesMyControl
> >
> > I think the VB would look like
> >     Public Class MyForm : Extends iUsesMyControl
> >
> > Your interface, iUsesMyControl, would look like:
> >     internal interface iUsesMyControl
> >     {
> >          int FormInt { get; set; }
> >          string FormString { get; set; }
> >     }
> >
> > Basically, we're defining two properties in the interface that all classes
> > implementing iUsesMyControl must implement. Check your VB documentation
> > for
> > how to define properties in an interface in VB.
> >
> > Your implementation of iUsesMyControl in your form would look like
> >
> >     private int formInt; // though this may have been previously defined
> > elsewhere.
> >     internal int FormInt
> >     {
> >          get { return formInt; }
> >          set { formInt = value; }
> >     }
> >
> >     private string formString;
> >     internal string FormString
> >     {
> >          get { return formString; }
> >          st { formString = value; }
> >     }
> >
> > Check your VB documentation for how to define the variables and expose
> > them
> > as properties in VB to accomplish the above C# code in VB.
> >
> > In your control, add a property:
> >
> >     private iUsesMyControl parentForm;
> >     internal iUsesMyControl ParentForm
> >     {
> >          set { parentForm = value; }
> >     }
> >
> > Somewhere early in your parent form, perhaps the load event, add
> >     myControl.ParentForm = (iUsesMyControl)this;
> >
> > This passes the MyForm to MyControl but by casting to iUsesMyControl it
> > tells MyControl only about the two variables defined in iUsesMyControl. I
> > think this, in VB would be:
> >     myControl.ParentForm = CType(Me, iUsesMyControl)
> >
> > Now, in your control, you have available:
> >     parentForm.FormInt
> > and
> >     parentForm.FormString
> >
> >
> > --
> > Dale Preston
> > MCAD C#
> > MCSE, MCDBA
> >
> >
> > "Zahid Hayat" wrote:
> >
> >> First I would like to thank both of you for replying to my question. As I
> >> do
> >> not have any experience with interfaces, therefore if you can provide an
> >> example I will be greatfull.
> >>
> >> Zahid.
> >>
> >>
> >>
> >> "Dale" wrote:
> >>
> >> > You can create a property in the control and then, when the parent form
> >> > initializes the control or changes the value of the variable, set the
> >> > value
> >> > of the property in the control.
> >> >
> >> > Though, like Ciaran says, it is not very object oriented, I have had
> >> > cases
> >> > where I had to pass the parent form as a property to a control. To get
> >> > around the issue he identifies of the control being used in a different
> >> > form,
> >> > then you create an interface for the data that the control requires
> >> > from its
> >> > parent and implement that interface in all parents that use that
> >> > control. In
> >> > that way, by casting to the interface type, you can make any form that
> >> > uses
> >> > your control into something you can use inside your control.
> >> >
> >> > HTH
> >> >
> >> > Dale
> >> > --
> >> > Dale Preston
> >> > MCAD C#
> >> > MCSE, MCDBA
> >> >
> >> >
> >> > "Zahid Hayat" wrote:
> >> >
> >> > > Is it possible to access value of a variable in Parent Form within
> >> > > control at
> >> > > runtime?
> >> > > Please provide an example (possibly in VB).
>
>
>

19 Nov 2006 7:12 PM

RobinS

Well, I was just trying to translate from C# to VB for you, but I've gone
back and reread the whole thread. If all you want is to be able to
get some kind of information from the parent form in which the control
resides, i'd think you could just add a public property to the parent form.

If Form1 implements an interface, it means that you must provide the
code for the properties defined in the interface. I think the line

> myControl = DirectCast(Me, iUsesMyControl)

allows you to access the methods and properties in the interface
from the control. I think what this allows you to do is set the
properties in the form that implement the interface to private.
Then casting myControl to that interface allows it to see the
private properties. So only the control can see the properties,
not the whole project. So in the control, maybe you could access
myControl.FormInt and myControl.FormString and see the
properties from the form.

Can anybody verify that I'm understanding that right?

However, I don't really see the need for something this complicated
if all you are trying to do is provide the ability for the control
to see something in the form. I would think you could just add a
property to the form, and let the control access it. The code
you have for the properties (which are public) should work okay.
Then in your control, I would think you could access the
properties as Form1.FormInt and Form1.FormString.
I guess it depends on whether it's okay to make those
properties public to the rest of the project or not.

Hope that helps. If anybody can shed some wisdom here,
that would be great.

Thanks,
Robin S.

Show quote

"Zahid Hayat" <ZahidHa***@discussions.microsoft.com> wrote in message
news:9A6BB7EC-1ED6-43D6-BBA8-70328817CF0B@microsoft.com...
> My parent Form looks like this:
> =======================
> Public Class Form1
>    Implements iUsesMyControl
>    Private _formInt As Integer
>    Private _formString As String
>    Public var1 As Integer
>    Private mycontrol As ContainerControl
>
>    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles MyBase.Load
>
>        _formInt = 123
>        _formString = "Zahid"
>        mycontrol = DirectCast(Me, iUsesMyControl)
>
>    End Sub
>
>    Public Property FormInt() As Integer Implements iUsesMyControl.FormInt
>        Get
>            Return _formInt
>        End Get
>        Set(ByVal value As Integer)
>            _formInt = value
>        End Set
>    End Property
>
>    Public Property FormString() As String Implements
> iUsesMyControl.FormString
>        Get
>            Return _formString
>        End Get
>        Set(ByVal value As String)
>            _formString = value
>        End Set
>    End Property
> End Class
> ============
>
> I do not understand the implements of Control itself. Do we need to
> implement another interface 'iUsesMyControl' as we did in the parent from
> (Form1)?
>
>
>
>
>
>
> "RobinS" wrote:
>
>> I think this would be the VB code for that:
>>
>> In your form, add an Implements for the interface, and add the
>> properties.
>> You will want to have private variables to keep the current value,
>> you are exposing them through a property.
>>
>>     public class MyFrom
>>         Implements iUsesMyControl
>>
>>         Private _FormInt as Integer
>>         Public Property FormInt() As Integer Implements
>> IUsesMyControl.FormInt
>>             Get
>>                 return _FormInt
>>             End Get
>>             Set(ByVal value As String)
>>                 _FormInt = value
>>             End Set
>>         End Function
>>         Private _FormString as String
>>         Public Property FormString() As String Implements
>> IUsesMyControl.FormString
>>             Get
>>                 return _FormString
>>             End Get
>>             Set(ByVal value As String)
>>                 _FormString = value
>>             End Set
>>         End Function
>>         ....(other form code)
>>     End Class
>>
>> Public Interface IUsesMyControl
>>     Property FormInt as Integer
>>     Property FormString as String
>> End Interface
>>
>> In your control:
>>     '**I'm not sure about this; Either I have it wrong,
>>     '** or there's some way to define something as
>>     '** an interface. If this doesn't work, try
>>     '** "implements IUsesMyControl" instead of "as IUsesMyControl".
>>     Private _parentForm as IUsesMyControl
>>     Public Readonly Property ParentForm as IUsesMyControl
>>         Set
>>             _parentForm = value
>>         End Set
>>     End Property
>>
>> Somewhere early in your parent form
>>     myControl.ParentForm = DirectCast(me, IUsesMyControl)
>>
>> I think that's right; feel free to correct me if I got any of it wrong.
>> Robin S.
>> -------------------------
>> "Dale" <dale0973@nospam.nospam> wrote in message
>> news:6AD37C2A-C539-45DB-BE10-E733ACEBC094@microsoft.com...
>> > Unfortunately, I am not a VB.Net developer but you should hopefully be
>> > able
>> > to figure this out from the C#.
>> >
>> > Let's say that your control is MyControl and your form is MyForm. The
>> > instance, in my example, of MyControl is named myControl. Assume your
>> > form
>> > needs a string variable we'll call formString and an int variable we'll
>> > call
>> > formInt that are defined in the parent form. Create an interface
>> > called,
>> > for
>> > instance, iUsesMyControl.
>> >
>> > In your form class declaration, change
>> >     public class MyForm : Form
>> >
>> > to
>> >     public class MyForm : Form, iUsesMyControl
>> >
>> > I think the VB would look like
>> >     Public Class MyForm : Extends iUsesMyControl
>> >
>> > Your interface, iUsesMyControl, would look like:
>> >     internal interface iUsesMyControl
>> >     {
>> >          int FormInt { get; set; }
>> >          string FormString { get; set; }
>> >     }
>> >
>> > Basically, we're defining two properties in the interface that all
>> > classes
>> > implementing iUsesMyControl must implement. Check your VB
>> > documentation
>> > for
>> > how to define properties in an interface in VB.
>> >
>> > Your implementation of iUsesMyControl in your form would look like
>> >
>> >     private int formInt; // though this may have been previously
>> > defined
>> > elsewhere.
>> >     internal int FormInt
>> >     {
>> >          get { return formInt; }
>> >          set { formInt = value; }
>> >     }
>> >
>> >     private string formString;
>> >     internal string FormString
>> >     {
>> >          get { return formString; }
>> >          st { formString = value; }
>> >     }
>> >
>> > Check your VB documentation for how to define the variables and expose
>> > them
>> > as properties in VB to accomplish the above C# code in VB.
>> >
>> > In your control, add a property:
>> >
>> >     private iUsesMyControl parentForm;
>> >     internal iUsesMyControl ParentForm
>> >     {
>> >          set { parentForm = value; }
>> >     }
>> >
>> > Somewhere early in your parent form, perhaps the load event, add
>> >     myControl.ParentForm = (iUsesMyControl)this;
>> >
>> > This passes the MyForm to MyControl but by casting to iUsesMyControl it
>> > tells MyControl only about the two variables defined in iUsesMyControl.
>> > I
>> > think this, in VB would be:
>> >     myControl.ParentForm = CType(Me, iUsesMyControl)
>> >
>> > Now, in your control, you have available:
>> >     parentForm.FormInt
>> > and
>> >     parentForm.FormString
>> >
>> >
>> > --
>> > Dale Preston
>> > MCAD C#
>> > MCSE, MCDBA
>> >
>> >
>> > "Zahid Hayat" wrote:
>> >
>> >> First I would like to thank both of you for replying to my question.
>> >> As I
>> >> do
>> >> not have any experience with interfaces, therefore if you can provide
>> >> an
>> >> example I will be greatfull.
>> >>
>> >> Zahid.
>> >>
>> >>
>> >>
>> >> "Dale" wrote:
>> >>
>> >> > You can create a property in the control and then, when the parent
>> >> > form
>> >> > initializes the control or changes the value of the variable, set
>> >> > the
>> >> > value
>> >> > of the property in the control.
>> >> >
>> >> > Though, like Ciaran says, it is not very object oriented, I have had
>> >> > cases
>> >> > where I had to pass the parent form as a property to a control. To
>> >> > get
>> >> > around the issue he identifies of the control being used in a
>> >> > different
>> >> > form,
>> >> > then you create an interface for the data that the control requires
>> >> > from its
>> >> > parent and implement that interface in all parents that use that
>> >> > control. In
>> >> > that way, by casting to the interface type, you can make any form
>> >> > that
>> >> > uses
>> >> > your control into something you can use inside your control.
>> >> >
>> >> > HTH
>> >> >
>> >> > Dale
>> >> > --
>> >> > Dale Preston
>> >> > MCAD C#
>> >> > MCSE, MCDBA
>> >> >
>> >> >
>> >> > "Zahid Hayat" wrote:
>> >> >
>> >> > > Is it possible to access value of a variable in Parent Form within
>> >> > > control at
>> >> > > runtime?
>> >> > > Please provide an example (possibly in VB).
>>
>>
>>

2 Dec 2006 6:00 AM

Zahid Hayat

I am developing this project using VisualStudio2005. The control is developed
independently and is not a part of the project (form1). I will add it to list
of controls in VS2005 and then drop it on the form where ever desired. The
problem is that the control is not awair of either the iUsesMycontrol
interface nor the the form1.

Show quote

"RobinS" wrote:

> Well, I was just trying to translate from C# to VB for you, but I've gone
> back and reread the whole thread. If all you want is to be able to
> get some kind of information from the parent form in which the control
> resides, i'd think you could just add a public property to the parent form.
>
> If Form1 implements an interface, it means that you must provide the
> code for the properties defined in the interface. I think the line
> >    myControl = DirectCast(Me, iUsesMyControl)
> allows you to access the methods and properties in the interface
> from the control. I think what this allows you to do is set the
> properties in the form that implement the interface to private.
> Then casting myControl to that interface allows it to see the
> private properties. So only the control can see the properties,
> not the whole project. So in the control, maybe you could access
> myControl.FormInt and myControl.FormString and see the
> properties from the form.
>
> Can anybody verify that I'm understanding that right?
>
> However, I don't really see the need for something this complicated
> if all you are trying to do is provide the ability for the control
> to see something in the form. I would think you could just add a
> property to the form, and let the control access it. The code
> you have for the properties (which are public) should work okay.
> Then in your control, I would think you could access the
> properties as Form1.FormInt and Form1.FormString.
> I guess it depends on whether it's okay to make those
> properties public to the rest of the project or not.
>
> Hope that helps. If anybody can shed some wisdom here,
> that would be great.
>
> Thanks,
> Robin S.
>
>
> "Zahid Hayat" <ZahidHa***@discussions.microsoft.com> wrote in message
> news:9A6BB7EC-1ED6-43D6-BBA8-70328817CF0B@microsoft.com...
> > My parent Form looks like this:
> > =======================
> > Public Class Form1
> >    Implements iUsesMyControl
> >    Private _formInt As Integer
> >    Private _formString As String
> >    Public var1 As Integer
> >    Private mycontrol As ContainerControl
> >
> >    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
> > System.EventArgs) Handles MyBase.Load
> >
> >        _formInt = 123
> >        _formString = "Zahid"
> >        mycontrol = DirectCast(Me, iUsesMyControl)
> >
> >    End Sub
> >
> >    Public Property FormInt() As Integer Implements iUsesMyControl.FormInt
> >        Get
> >            Return _formInt
> >        End Get
> >        Set(ByVal value As Integer)
> >            _formInt = value
> >        End Set
> >    End Property
> >
> >    Public Property FormString() As String Implements
> > iUsesMyControl.FormString
> >        Get
> >            Return _formString
> >        End Get
> >        Set(ByVal value As String)
> >            _formString = value
> >        End Set
> >    End Property
> > End Class
> > ============
> >
> > I do not understand the implements of Control itself. Do we need to
> > implement another interface 'iUsesMyControl' as we did in the parent from
> > (Form1)?
> >
> >
> >
> >
> >
> >
> > "RobinS" wrote:
> >
> >> I think this would be the VB code for that:
> >>
> >> In your form, add an Implements for the interface, and add the
> >> properties.
> >> You will want to have private variables to keep the current value,
> >> you are exposing them through a property.
> >>
> >>     public class MyFrom
> >>         Implements iUsesMyControl
> >>
> >>         Private _FormInt as Integer
> >>         Public Property FormInt() As Integer Implements
> >> IUsesMyControl.FormInt
> >>             Get
> >>                 return _FormInt
> >>             End Get
> >>             Set(ByVal value As String)
> >>                 _FormInt = value
> >>             End Set
> >>         End Function
> >>         Private _FormString as String
> >>         Public Property FormString() As String Implements
> >> IUsesMyControl.FormString
> >>             Get
> >>                 return _FormString
> >>             End Get
> >>             Set(ByVal value As String)
> >>                 _FormString = value
> >>             End Set
> >>         End Function
> >>         ....(other form code)
> >>     End Class
> >>
> >> Public Interface IUsesMyControl
> >>     Property FormInt as Integer
> >>     Property FormString as String
> >> End Interface
> >>
> >> In your control:
> >>     '**I'm not sure about this; Either I have it wrong,
> >>     '** or there's some way to define something as
> >>     '** an interface. If this doesn't work, try
> >>     '** "implements IUsesMyControl" instead of "as IUsesMyControl".
> >>     Private _parentForm as IUsesMyControl
> >>     Public Readonly Property ParentForm as IUsesMyControl
> >>         Set
> >>             _parentForm = value
> >>         End Set
> >>     End Property
> >>
> >> Somewhere early in your parent form
> >>     myControl.ParentForm = DirectCast(me, IUsesMyControl)
> >>
> >> I think that's right; feel free to correct me if I got any of it wrong.
> >> Robin S.
> >> -------------------------
> >> "Dale" <dale0973@nospam.nospam> wrote in message
> >> news:6AD37C2A-C539-45DB-BE10-E733ACEBC094@microsoft.com...
> >> > Unfortunately, I am not a VB.Net developer but you should hopefully be
> >> > able
> >> > to figure this out from the C#.
> >> >
> >> > Let's say that your control is MyControl and your form is MyForm. The
> >> > instance, in my example, of MyControl is named myControl. Assume your
> >> > form
> >> > needs a string variable we'll call formString and an int variable we'll
> >> > call
> >> > formInt that are defined in the parent form. Create an interface
> >> > called,
> >> > for
> >> > instance, iUsesMyControl.
> >> >
> >> > In your form class declaration, change
> >> >     public class MyForm : Form
> >> >
> >> > to
> >> >     public class MyForm : Form, iUsesMyControl
> >> >
> >> > I think the VB would look like
> >> >     Public Class MyForm : Extends iUsesMyControl
> >> >
> >> > Your interface, iUsesMyControl, would look like:
> >> >     internal interface iUsesMyControl
> >> >     {
> >> >          int FormInt { get; set; }
> >> >          string FormString { get; set; }
> >> >     }
> >> >
> >> > Basically, we're defining two properties in the interface that all
> >> > classes
> >> > implementing iUsesMyControl must implement. Check your VB
> >> > documentation
> >> > for
> >> > how to define properties in an interface in VB.
> >> >
> >> > Your implementation of iUsesMyControl in your form would look like
> >> >
> >> >     private int formInt; // though this may have been previously
> >> > defined
> >> > elsewhere.
> >> >     internal int FormInt
> >> >     {
> >> >          get { return formInt; }
> >> >          set { formInt = value; }
> >> >     }
> >> >
> >> >     private string formString;
> >> >     internal string FormString
> >> >     {
> >> >          get { return formString; }
> >> >          st { formString = value; }
> >> >     }
> >> >
> >> > Check your VB documentation for how to define the variables and expose
> >> > them
> >> > as properties in VB to accomplish the above C# code in VB.
> >> >
> >> > In your control, add a property:
> >> >
> >> >     private iUsesMyControl parentForm;
> >> >     internal iUsesMyControl ParentForm
> >> >     {
> >> >          set { parentForm = value; }
> >> >     }
> >> >
> >> > Somewhere early in your parent form, perhaps the load event, add
> >> >     myControl.ParentForm = (iUsesMyControl)this;
> >> >
> >> > This passes the MyForm to MyControl but by casting to iUsesMyControl it
> >> > tells MyControl only about the two variables defined in iUsesMyControl.
> >> > I
> >> > think this, in VB would be:
> >> >     myControl.ParentForm = CType(Me, iUsesMyControl)
> >> >
> >> > Now, in your control, you have available:
> >> >     parentForm.FormInt
> >> > and
> >> >     parentForm.FormString
> >> >
> >> >
> >> > --
> >> > Dale Preston
> >> > MCAD C#
> >> > MCSE, MCDBA
> >> >
> >> >
> >> > "Zahid Hayat" wrote:
> >> >
> >> >> First I would like to thank both of you for replying to my question.
> >> >> As I
> >> >> do
> >> >> not have any experience with interfaces, therefore if you can provide
> >> >> an
> >> >> example I will be greatfull.
> >> >>
> >> >> Zahid.
> >> >>
> >> >>
> >> >>
> >> >> "Dale" wrote:
> >> >>
> >> >> > You can create a property in the control and then, when the parent
> >> >> > form
> >> >> > initializes the control or changes the value of the variable, set
> >> >> > the
> >> >> > value
> >> >> > of the property in the control.
> >> >> >
> >> >> > Though, like Ciaran says, it is not very object oriented, I have had
> >> >> > cases
> >> >> > where I had to pass the parent form as a property to a control. To
> >> >> > get
> >> >> > around the issue he identifies of the control being used in a
> >> >> > different
> >> >> > form,
> >> >> > then you create an interface for the data that the control requires
> >> >> > from its
> >> >> > parent and implement that interface in all parents that use that
> >> >> > control. In
> >> >> > that way, by casting to the interface type, you can make any form
> >> >> > that
> >> >> > uses
> >> >> > your control into something you can use inside your control.
> >> >> >
> >> >> > HTH
> >> >> >
> >> >> > Dale
> >> >> > --
> >> >> > Dale Preston
> >> >> > MCAD C#
> >> >> > MCSE, MCDBA
> >> >> >
> >> >> >
> >> >> > "Zahid Hayat" wrote:
> >> >> >
> >> >> > > Is it possible to access value of a variable in Parent Form within
> >> >> > > control at
> >> >> > > runtime?
> >> >> > > Please provide an example (possibly in VB).
> >>
> >>
> >>
>
>
>

2 Dec 2006 4:08 PM

RobinS

I don't know the answer to your question. You might try posting it
in microsoft.public.dotnet.framework.windowsforms and
microsoft.public.dotnet.framework.windowsforms.controls
and see if anyone else can help. Please post it to both groups
at once, so if someone in one group answers it, people in
the other group will also be able to see the answer.

Robin S.
---------------------------------------------
Show quote

"Zahid Hayat" <ZahidHa***@discussions.microsoft.com> wrote in message
news:AEC52FC1-B9A2-40B0-91C9-01E32470B961@microsoft.com...
>I am developing this project using VisualStudio2005. The control is
>developed
> independently and is not a part of the project (form1). I will add it to
> list
> of controls in VS2005 and then drop it on the form where ever desired. The
> problem is that the control is not awair of either the iUsesMycontrol
> interface nor the the form1.
>
>
> "RobinS" wrote:
>
>> Well, I was just trying to translate from C# to VB for you, but I've gone
>> back and reread the whole thread. If all you want is to be able to
>> get some kind of information from the parent form in which the control
>> resides, i'd think you could just add a public property to the parent
>> form.
>>
>> If Form1 implements an interface, it means that you must provide the
>> code for the properties defined in the interface. I think the line
>> >    myControl = DirectCast(Me, iUsesMyControl)
>> allows you to access the methods and properties in the interface
>> from the control. I think what this allows you to do is set the
>> properties in the form that implement the interface to private.
>> Then casting myControl to that interface allows it to see the
>> private properties. So only the control can see the properties,
>> not the whole project. So in the control, maybe you could access
>> myControl.FormInt and myControl.FormString and see the
>> properties from the form.
>>
>> Can anybody verify that I'm understanding that right?
>>
>> However, I don't really see the need for something this complicated
>> if all you are trying to do is provide the ability for the control
>> to see something in the form. I would think you could just add a
>> property to the form, and let the control access it. The code
>> you have for the properties (which are public) should work okay.
>> Then in your control, I would think you could access the
>> properties as Form1.FormInt and Form1.FormString.
>> I guess it depends on whether it's okay to make those
>> properties public to the rest of the project or not.
>>
>> Hope that helps. If anybody can shed some wisdom here,
>> that would be great.
>>
>> Thanks,
>> Robin S.
>>
>>
>> "Zahid Hayat" <ZahidHa***@discussions.microsoft.com> wrote in message
>> news:9A6BB7EC-1ED6-43D6-BBA8-70328817CF0B@microsoft.com...
>> > My parent Form looks like this:
>> > =======================
>> > Public Class Form1
>> >    Implements iUsesMyControl
>> >    Private _formInt As Integer
>> >    Private _formString As String
>> >    Public var1 As Integer
>> >    Private mycontrol As ContainerControl
>> >
>> >    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
>> > System.EventArgs) Handles MyBase.Load
>> >
>> >        _formInt = 123
>> >        _formString = "Zahid"
>> >        mycontrol = DirectCast(Me, iUsesMyControl)
>> >
>> >    End Sub
>> >
>> >    Public Property FormInt() As Integer Implements
>> > iUsesMyControl.FormInt
>> >        Get
>> >            Return _formInt
>> >        End Get
>> >        Set(ByVal value As Integer)
>> >            _formInt = value
>> >        End Set
>> >    End Property
>> >
>> >    Public Property FormString() As String Implements
>> > iUsesMyControl.FormString
>> >        Get
>> >            Return _formString
>> >        End Get
>> >        Set(ByVal value As String)
>> >            _formString = value
>> >        End Set
>> >    End Property
>> > End Class
>> > ============
>> >
>> > I do not understand the implements of Control itself. Do we need to
>> > implement another interface 'iUsesMyControl' as we did in the parent
>> > from
>> > (Form1)?
>> >
>> >
>> >
>> >
>> >
>> >
>> > "RobinS" wrote:
>> >
>> >> I think this would be the VB code for that:
>> >>
>> >> In your form, add an Implements for the interface, and add the
>> >> properties.
>> >> You will want to have private variables to keep the current value,
>> >> you are exposing them through a property.
>> >>
>> >>     public class MyFrom
>> >>         Implements iUsesMyControl
>> >>
>> >>         Private _FormInt as Integer
>> >>         Public Property FormInt() As Integer Implements
>> >> IUsesMyControl.FormInt
>> >>             Get
>> >>                 return _FormInt
>> >>             End Get
>> >>             Set(ByVal value As String)
>> >>                 _FormInt = value
>> >>             End Set
>> >>         End Function
>> >>         Private _FormString as String
>> >>         Public Property FormString() As String Implements
>> >> IUsesMyControl.FormString
>> >>             Get
>> >>                 return _FormString
>> >>             End Get
>> >>             Set(ByVal value As String)
>> >>                 _FormString = value
>> >>             End Set
>> >>         End Function
>> >>         ....(other form code)
>> >>     End Class
>> >>
>> >> Public Interface IUsesMyControl
>> >>     Property FormInt as Integer
>> >>     Property FormString as String
>> >> End Interface
>> >>
>> >> In your control:
>> >>     '**I'm not sure about this; Either I have it wrong,
>> >>     '** or there's some way to define something as
>> >>     '** an interface. If this doesn't work, try
>> >>     '** "implements IUsesMyControl" instead of "as IUsesMyControl".
>> >>     Private _parentForm as IUsesMyControl
>> >>     Public Readonly Property ParentForm as IUsesMyControl
>> >>         Set
>> >>             _parentForm = value
>> >>         End Set
>> >>     End Property
>> >>
>> >> Somewhere early in your parent form
>> >>     myControl.ParentForm = DirectCast(me, IUsesMyControl)
>> >>
>> >> I think that's right; feel free to correct me if I got any of it
>> >> wrong.
>> >> Robin S.
>> >> -------------------------
>> >> "Dale" <dale0973@nospam.nospam> wrote in message
>> >> news:6AD37C2A-C539-45DB-BE10-E733ACEBC094@microsoft.com...
>> >> > Unfortunately, I am not a VB.Net developer but you should hopefully
>> >> > be
>> >> > able
>> >> > to figure this out from the C#.
>> >> >
>> >> > Let's say that your control is MyControl and your form is MyForm.
>> >> > The
>> >> > instance, in my example, of MyControl is named myControl. Assume
>> >> > your
>> >> > form
>> >> > needs a string variable we'll call formString and an int variable
>> >> > we'll
>> >> > call
>> >> > formInt that are defined in the parent form. Create an interface
>> >> > called,
>> >> > for
>> >> > instance, iUsesMyControl.
>> >> >
>> >> > In your form class declaration, change
>> >> >     public class MyForm : Form
>> >> >
>> >> > to
>> >> >     public class MyForm : Form, iUsesMyControl
>> >> >
>> >> > I think the VB would look like
>> >> >     Public Class MyForm : Extends iUsesMyControl
>> >> >
>> >> > Your interface, iUsesMyControl, would look like:
>> >> >     internal interface iUsesMyControl
>> >> >     {
>> >> >          int FormInt { get; set; }
>> >> >          string FormString { get; set; }
>> >> >     }
>> >> >
>> >> > Basically, we're defining two properties in the interface that all
>> >> > classes
>> >> > implementing iUsesMyControl must implement. Check your VB
>> >> > documentation
>> >> > for
>> >> > how to define properties in an interface in VB.
>> >> >
>> >> > Your implementation of iUsesMyControl in your form would look like
>> >> >
>> >> >     private int formInt; // though this may have been previously
>> >> > defined
>> >> > elsewhere.
>> >> >     internal int FormInt
>> >> >     {
>> >> >          get { return formInt; }
>> >> >          set { formInt = value; }
>> >> >     }
>> >> >
>> >> >     private string formString;
>> >> >     internal string FormString
>> >> >     {
>> >> >          get { return formString; }
>> >> >          st { formString = value; }
>> >> >     }
>> >> >
>> >> > Check your VB documentation for how to define the variables and
>> >> > expose
>> >> > them
>> >> > as properties in VB to accomplish the above C# code in VB.
>> >> >
>> >> > In your control, add a property:
>> >> >
>> >> >     private iUsesMyControl parentForm;
>> >> >     internal iUsesMyControl ParentForm
>> >> >     {
>> >> >          set { parentForm = value; }
>> >> >     }
>> >> >
>> >> > Somewhere early in your parent form, perhaps the load event, add
>> >> >     myControl.ParentForm = (iUsesMyControl)this;
>> >> >
>> >> > This passes the MyForm to MyControl but by casting to iUsesMyControl
>> >> > it
>> >> > tells MyControl only about the two variables defined in
>> >> > iUsesMyControl.
>> >> > I
>> >> > think this, in VB would be:
>> >> >     myControl.ParentForm = CType(Me, iUsesMyControl)
>> >> >
>> >> > Now, in your control, you have available:
>> >> >     parentForm.FormInt
>> >> > and
>> >> >     parentForm.FormString
>> >> >
>> >> >
>> >> > --
>> >> > Dale Preston
>> >> > MCAD C#
>> >> > MCSE, MCDBA
>> >> >
>> >> >
>> >> > "Zahid Hayat" wrote:
>> >> >
>> >> >> First I would like to thank both of you for replying to my
>> >> >> question.
>> >> >> As I
>> >> >> do
>> >> >> not have any experience with interfaces, therefore if you can
>> >> >> provide
>> >> >> an
>> >> >> example I will be greatfull.
>> >> >>
>> >> >> Zahid.
>> >> >>
>> >> >>
>> >> >>
>> >> >> "Dale" wrote:
>> >> >>
>> >> >> > You can create a property in the control and then, when the
>> >> >> > parent
>> >> >> > form
>> >> >> > initializes the control or changes the value of the variable, set
>> >> >> > the
>> >> >> > value
>> >> >> > of the property in the control.
>> >> >> >
>> >> >> > Though, like Ciaran says, it is not very object oriented, I have
>> >> >> > had
>> >> >> > cases
>> >> >> > where I had to pass the parent form as a property to a control.
>> >> >> > To
>> >> >> > get
>> >> >> > around the issue he identifies of the control being used in a
>> >> >> > different
>> >> >> > form,
>> >> >> > then you create an interface for the data that the control
>> >> >> > requires
>> >> >> > from its
>> >> >> > parent and implement that interface in all parents that use that
>> >> >> > control. In
>> >> >> > that way, by casting to the interface type, you can make any form
>> >> >> > that
>> >> >> > uses
>> >> >> > your control into something you can use inside your control.
>> >> >> >
>> >> >> > HTH
>> >> >> >
>> >> >> > Dale
>> >> >> > --
>> >> >> > Dale Preston
>> >> >> > MCAD C#
>> >> >> > MCSE, MCDBA
>> >> >> >
>> >> >> >
>> >> >> > "Zahid Hayat" wrote:
>> >> >> >
>> >> >> > > Is it possible to access value of a variable in Parent Form
>> >> >> > > within
>> >> >> > > control at
>> >> >> > > runtime?
>> >> >> > > Please provide an example (possibly in VB).
>> >>
>> >>
>> >>
>>
>>
>>