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When do you call DataGrid.DataBind()Sometimes, you call DataGrid.DataBind() after doing a
DataGrid.DataSource = DataSet (or reader) and sometimes you don't. When is it that you have to call DataBind on the datagrid and when is it not necessary? Why is there the difference? You should call Databind on a DataGrid after any modifications to the grid's
data source (record added, deleted, updated, etc.) As for sometimes calling databind after setting the data source and sometimes not...Who said you should not be databinding after setting the data source? What you don't do is call DataBind in the Postback section of Page_Load. The reason being is that the page is being reloaded for a reason. It could have been that the user switch the page of data they want to see, the user may have initiated a sort, the user may have deleted a row or updated a row. All of these actions will force a postback. Page_Load will run early on in the Postback process, so you'll want to set your datasource for your grid up there, but don't databind here, because after Page_Load, the event that caused the postback is going to fire (say the SortCommand event, for example). If you bind in the Page_Load and then the SortCommand event fires, you'd have to call DataBind again in the SortCommand event (because you just changed what the grid is showing). So, on Postback's, you re-set the grid's datasource in Page_Load, but put the Databind in the grid's event handlers. Show quote "Water Cooler v2" <wtr_***@yahoo.com> wrote in message news:1149540251.830751.94550@u72g2000cwu.googlegroups.com... > Sometimes, you call DataGrid.DataBind() after doing a > > DataGrid.DataSource = DataSet (or reader) > > and sometimes you don't. When is it that you have to call DataBind on > the datagrid and when is it not necessary? Why is there the difference? > Scott M. wrote:
Show quote > You should call Databind on a DataGrid after any modifications to the grid's After setting a datasource, if i use the data adaptor's fill() command> data source (record added, deleted, updated, etc.) > > As for sometimes calling databind after setting the data source and > sometimes not...Who said you should not be databinding after setting the > data source? > > What you don't do is call DataBind in the Postback section of Page_Load. > The reason being is that the page is being reloaded for a reason. It could > have been that the user switch the page of data they want to see, the user > may have initiated a sort, the user may have deleted a row or updated a row. > All of these actions will force a postback. Page_Load will run early on in > the Postback process, so you'll want to set your datasource for your grid up > there, but don't databind here, because after Page_Load, the event that > caused the postback is going to fire (say the SortCommand event, for > example). If you bind in the Page_Load and then the SortCommand event > fires, you'd have to call DataBind again in the SortCommand event (because > you just changed what the grid is showing). So, on Postback's, you re-set > the grid's datasource in Page_Load, but put the Databind in the grid's event > handlers. > > "Water Cooler v2" <wtr_***@yahoo.com> wrote in message > news:1149540251.830751.94550@u72g2000cwu.googlegroups.com... > > Sometimes, you call DataGrid.DataBind() after doing a > > > > DataGrid.DataSource = DataSet (or reader) > > > > and sometimes you don't. When is it that you have to call DataBind on > > the datagrid and when is it not necessary? Why is there the difference? > > >Who said you should not be databinding after setting the data source? to fill the dataset (which is the datagrid's datasource) there seems to be no need for a databinding. I've been wondering what it actually does, being i seem not to need it. B. There are 3 elements to making this work:
1. The actual data repository (a database?) 2. The in-memory representation of the original data (a dataset) 3. The user interface for the data (the DataGrid). The original data needs to be replicated into the in-memory container (the DataSet). This is accomplished by calling the .Fill() method of your DataAdapter. Now, the DataGrid needs to be "connected" to the in-memory data (the DataSet). You must set the DataGrid's datasource property so it knows where to get the data from, but just setting the datasource doesn't actually go and get any data. So, you need to call the DataGrid's DataBind method to tell the grid to go and look at the data (specified in the DataSource property) and bind to it. If the data in the DataSet ever gets changed in any way, or if you want to show the existing data in a different way (a different page of data or a different sorted view of the data), you are going to need to have the DataGrid "refresh" its representation of that underlying data. Calling DataBind does just that. Show quote "Brian Tkatch" <Maxwell_Sm***@ThePentagon.com> wrote in message news:1149601978.989383.63810@c74g2000cwc.googlegroups.com... > > Scott M. wrote: >> You should call Databind on a DataGrid after any modifications to the >> grid's >> data source (record added, deleted, updated, etc.) >> >> As for sometimes calling databind after setting the data source and >> sometimes not...Who said you should not be databinding after setting the >> data source? >> >> What you don't do is call DataBind in the Postback section of Page_Load. >> The reason being is that the page is being reloaded for a reason. It >> could >> have been that the user switch the page of data they want to see, the >> user >> may have initiated a sort, the user may have deleted a row or updated a >> row. >> All of these actions will force a postback. Page_Load will run early on >> in >> the Postback process, so you'll want to set your datasource for your grid >> up >> there, but don't databind here, because after Page_Load, the event that >> caused the postback is going to fire (say the SortCommand event, for >> example). If you bind in the Page_Load and then the SortCommand event >> fires, you'd have to call DataBind again in the SortCommand event >> (because >> you just changed what the grid is showing). So, on Postback's, you >> re-set >> the grid's datasource in Page_Load, but put the Databind in the grid's >> event >> handlers. >> >> "Water Cooler v2" <wtr_***@yahoo.com> wrote in message >> news:1149540251.830751.94550@u72g2000cwu.googlegroups.com... >> > Sometimes, you call DataGrid.DataBind() after doing a >> > >> > DataGrid.DataSource = DataSet (or reader) >> > >> > and sometimes you don't. When is it that you have to call DataBind on >> > the datagrid and when is it not necessary? Why is there the difference? >> > > >>Who said you should not be databinding after setting the data source? > > After setting a datasource, if i use the data adaptor's fill() command > to fill the dataset (which is the datagrid's datasource) there seems to > be no need for a databinding. > > I've been wondering what it actually does, being i seem not to need it. > > B. > Scott M. wrote:
> There are 3 elements to making this work: I think i will disagree with that. (Please correct me if i'm wrong!)> > 1. The actual data repository (a database?) > 2. The in-memory representation of the original data (a dataset) > 3. The user interface for the data (the DataGrid). The in-memory representation, is actually an in memory copy. The difference being, the copy changes, the original does not. And, this copy is a datatable, not a dataset. A dataset is the container for one or many datatables, however. (As well as dataviews and datarelations.) > The original data needs to be replicated into the in-memory container (the Which just runs the .SelectCommand command. It would have been *much*> DataSet). This is accomplished by calling the .Fill() method of your > DataAdapter. more clear had they named it "ExecuteSelectCommand" or "SelectCommandResultsInto" > Now, the DataGrid needs to be "connected" to the in-memory data (the It actually needs to be connacted to the dataview. If connected to the> DataSet). dataset, it just shows a plus-sign which expands into the availible dataviews, of which one must be selected to show any data. Further, connecting it to a dataset leaves those arrows on the caption bar. Connecting it directly to the dataview, however, does not. > You must set the DataGrid's datasource property so it knows where Yep, that confused me at first. Which is when i realized that the> to get the data from, but just setting the datasource doesn't actually go > and get any data. datagrid has absolutely nothing to do with a dataadaptor. A datagrid is a window into the dataview. A dataview is the resultset of a datatable (as opposed to the design). A datatable can be filled in many ways. One way is with a select statement. One way to run a select statement is via the Fill() command of a dataadaptor. > So, you need to call the DataGrid's DataBind method to When it is set it looks. Databind is not needed, as i expreessed> tell the grid to go and look at the data (specified in the DataSource > property) and bind to it. earlier. > If the data in the DataSet ever gets changed in any way, or if you want to Actually, calling datagrid.refresh does that.> show the existing data in a different way (a different page of data or a > different sorted view of the data), you are going to need to have the > DataGrid "refresh" its representation of that underlying data. Calling > DataBind does just that. I still see no reason for databind. Hmm... unless it somehow "watches" it and refreshes for you. As a note, calling Fill() works both before and after setting the datagrid's datasource. That is, the FIll() command triggers the datagrid to refresh. However, using .Expression() does not. If done before the datasource is set, it shows the modified data, doing it after the datasource is set, requires a datagrid.refresh for it to be noticed. Anyway, i see datagrid.databindings which requires me a to enter a property name. I am a bit confused over exactly what this is. BTW, i appreciate the help in clarifying this. I've got to read, clarify, and test to figure this whole thing out. I'm still a bit confused. B. Show quote > > > > "Brian Tkatch" <Maxwell_Sm***@ThePentagon.com> wrote in message > news:1149601978.989383.63810@c74g2000cwc.googlegroups.com... > > > > Scott M. wrote: > >> You should call Databind on a DataGrid after any modifications to the > >> grid's > >> data source (record added, deleted, updated, etc.) > >> > >> As for sometimes calling databind after setting the data source and > >> sometimes not...Who said you should not be databinding after setting the > >> data source? > >> > >> What you don't do is call DataBind in the Postback section of Page_Load. > >> The reason being is that the page is being reloaded for a reason. It > >> could > >> have been that the user switch the page of data they want to see, the > >> user > >> may have initiated a sort, the user may have deleted a row or updated a > >> row. > >> All of these actions will force a postback. Page_Load will run early on > >> in > >> the Postback process, so you'll want to set your datasource for your grid > >> up > >> there, but don't databind here, because after Page_Load, the event that > >> caused the postback is going to fire (say the SortCommand event, for > >> example). If you bind in the Page_Load and then the SortCommand event > >> fires, you'd have to call DataBind again in the SortCommand event > >> (because > >> you just changed what the grid is showing). So, on Postback's, you > >> re-set > >> the grid's datasource in Page_Load, but put the Databind in the grid's > >> event > >> handlers. > >> > >> "Water Cooler v2" <wtr_***@yahoo.com> wrote in message > >> news:1149540251.830751.94550@u72g2000cwu.googlegroups.com... > >> > Sometimes, you call DataGrid.DataBind() after doing a > >> > > >> > DataGrid.DataSource = DataSet (or reader) > >> > > >> > and sometimes you don't. When is it that you have to call DataBind on > >> > the datagrid and when is it not necessary? Why is there the difference? > >> > > > > >>Who said you should not be databinding after setting the data source? > > > > After setting a datasource, if i use the data adaptor's fill() command > > to fill the dataset (which is the datagrid's datasource) there seems to > > be no need for a databinding. > > > > I've been wondering what it actually does, being i seem not to need it. > > > > B. > > > I think i will disagree with that. (Please correct me if i'm wrong!) This is correct and does not conflict with what I said in the first place. > > The in-memory representation, is actually an in memory copy. The > difference being, the copy changes, the original does not. And, this > copy is a datatable, not a dataset. A dataset is the container for one > or many datatables, however. (As well as dataviews and datarelations.) You've only expounded upon the structure of the DataSet, but for most purposes of conversation, it is correct to say that the DataSet is the in-memory representation, since the DataTable is in the DataSet. >> The original data needs to be replicated into the in-memory container You'll need to pass that suggestion along to MS, but that doesn't change the >> (the >> DataSet). This is accomplished by calling the .Fill() method of your >> DataAdapter. > > Which just runs the .SelectCommand command. It would have been *much* > more clear had they named it "ExecuteSelectCommand" or > "SelectCommandResultsInto" fact that calling .Fill() is how you populate the DataSet. >> Now, the DataGrid needs to be "connected" to the in-memory data (the You only need to connect a DataGrid to a DataView if you want to see the >> DataSet). > > It actually needs to be connacted to the dataview. If connected to the > dataset, it just shows a plus-sign which expands into the availible > dataviews, of which one must be selected to show any data. data differently than it is in the DataSet. You didn't mention that you were in need or using DataViews, so I didn't go into setting the DataGrid's data source to a DataView, but I have indicated that the DataGrid needs to have its data source set to the in-memory representation of the data. If that means DataView for you, then your data source is the DataView, rather then the DataSet. > Further, connecting it to a dataset leaves those arrows on the caption I'm not sure what you mean here. Are you using VS 2003 or 2005? Are you > bar. Connecting it directly to the dataview, however, does not. talking about the WinForms DataGrid or the WebForms DataGrid? >> You must set the DataGrid's datasource property so it knows where Well, not always. A DataGrid is a window into the in-memory representation >> to get the data from, but just setting the datasource doesn't actually go >> and get any data. > > Yep, that confused me at first. Which is when i realized that the > datagrid has absolutely nothing to do with a dataadaptor. A datagrid is > a window into the dataview. of the original data. It could be a DataView or it could be a DataTable directly or it could be a DataSet that holds a DataTable. > A dataview is the resultset of a datatable Not actually. A DataView holds no data whatsoever. It is simply a filtered > (as opposed to the design). A datatable can be filled in many ways. One > way is with a select statement. One way to run a select statement is > via the Fill() command of a dataadaptor. view of the in-memory representation of the data. >> So, you need to call the DataGrid's DataBind method to Again, I'll ask what version of .NET are you referring to? My responses are >> tell the grid to go and look at the data (specified in the DataSource >> property) and bind to it. > > When it is set it looks. Databind is not needed, as i expreessed > earlier. based on the 1.1 Framework, VS.NET 2003 and the WebForms DataGrid. In these versions, you MUST call .DataBind to get any data. >> If the data in the DataSet ever gets changed in any way, or if you want You are referring to the WinForms DataGrid aren't you? The WebForms >> to >> show the existing data in a different way (a different page of data or a >> different sorted view of the data), you are going to need to have the >> DataGrid "refresh" its representation of that underlying data. Calling >> DataBind does just that. > > Actually, calling datagrid.refresh does that. DataGrid does not have such a method. > I still see no reason for databind. In a WinForms app, you would only need DataBind on the initial DataGrid population. > As a note, calling Fill() works both before and after setting the Good luck.> datagrid's datasource. That is, the FIll() command triggers the > datagrid to refresh. However, using .Expression() does not. If done > before the datasource is set, it shows the modified data, doing it > after the datasource is set, requires a datagrid.refresh for it to be > noticed. > > Anyway, i see datagrid.databindings which requires me a to enter a > property name. I am a bit confused over exactly what this is. > > BTW, i appreciate the help in clarifying this. I've got to read, > clarify, and test to figure this whole thing out. I'm still a bit > confused. <snip>
> > Further, connecting it to a dataset leaves those arrows on the caption 2003, winforms.> > bar. Connecting it directly to the dataview, however, does not. > > I'm not sure what you mean here. Are you using VS 2003 or 2005? Are you > talking about the WinForms DataGrid or the WebForms DataGrid? > Well, not always. A DataGrid is a window into the in-memory representation Original? Why? AFAIK, the datagrid can change the data, now having two> of the original data. It could be a DataView or it could be a DataTable > directly or it could be a DataSet that holds a DataTable. sets, that are the orignal and the modified, and the datagrid shows the modified. > > A dataview is the resultset of a datatable Granted.> > (as opposed to the design). A datatable can be filled in many ways. One > > way is with a select statement. One way to run a select statement is > > via the Fill() command of a dataadaptor. > > Not actually. A DataView holds no data whatsoever. It is simply a filtered > view of the in-memory representation of the data. However, setting it to a datatable is the same thing as setting it to the datatable's defaultview. > >> So, you need to call the DataGrid's DataBind method to Ah, well, that explains it.> >> tell the grid to go and look at the data (specified in the DataSource > >> property) and bind to it. > > > > When it is set it looks. Databind is not needed, as i expreessed > > earlier. > > Again, I'll ask what version of .NET are you referring to? My responses are > based on the 1.1 Framework, VS.NET 2003 and the WebForms DataGrid. In these > versions, you MUST call .DataBind to get any data. It's all so confusing. :) <snip> > Nope. You never need to do it on winforms.> > I still see no reason for databind. > > In a WinForms app, you would only need DataBind on the initial DataGrid > population. I read some more about it. The purpose of databindings has to do with controls and returning values, like the bound column in Access. So, for example, if a combo box shows one column but returns the value of another, a databinding would need to be done to the column whose values are wanted. B. >> Well, not always. A DataGrid is a window into the in-memory But after modifying the datagrid (which modifies the in-memory >> representation >> of the original data. It could be a DataView or it could be a DataTable >> directly or it could be a DataSet that holds a DataTable. > > Original? Why? AFAIK, the datagrid can change the data, now having two > sets, that are the orignal and the modified, and the datagrid shows the > modified. representation of the original data) wouldn't you want that in-memory representation to update the original data (thereby putting the two back in sync)? Scott M. wrote:
> >> Well, not always. A DataGrid is a window into the in-memory If the user likes the changes, yes. Otherwise, no.> >> representation > >> of the original data. It could be a DataView or it could be a DataTable > >> directly or it could be a DataSet that holds a DataTable. > > > > Original? Why? AFAIK, the datagrid can change the data, now having two > > sets, that are the orignal and the modified, and the datagrid shows the > > modified. > > But after modifying the datagrid (which modifies the in-memory > representation of the original data) wouldn't you want that in-memory > representation to update the original data (thereby putting the two back in > sync)? B. Either way, the grid's data source and the original data will need to be
in-sync. Either both have the new/edited data or both remain unchanged. Updating the grid should update the original data and if that succeeds, the grid's data source should be updated. Show quote "Brian Tkatch" <Maxwell_Sm***@ThePentagon.com> wrote in message news:1150213831.943363.87160@c74g2000cwc.googlegroups.com... > > Scott M. wrote: >> >> Well, not always. A DataGrid is a window into the in-memory >> >> representation >> >> of the original data. It could be a DataView or it could be a >> >> DataTable >> >> directly or it could be a DataSet that holds a DataTable. >> > >> > Original? Why? AFAIK, the datagrid can change the data, now having two >> > sets, that are the orignal and the modified, and the datagrid shows the >> > modified. >> >> But after modifying the datagrid (which modifies the in-memory >> representation of the original data) wouldn't you want that in-memory >> representation to update the original data (thereby putting the two back >> in >> sync)? > > If the user likes the changes, yes. Otherwise, no. > > B. >  |
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