Weird error with NumericUpDown

microsoft.public.dotnet.framework

22 Jul 2006 10:02 AM

Stephan Zaubzer

Hi all,

I encountered a problem with NumericUpDown yesterday and managed to
reproduce the error with a very easy examle.
I have a Windows Application with only one Form, which contains only one
NumericUpDown control and nothing else.

This is the only code I wrote: (everything else was done with the
designer of Visual Studio).

private void numericUpDown1_ValueChanged(object sender, EventArgs e) {
     if (((NumericUpDown)sender).Value == 50) {
         MessageBox.Show("50 reached");
     }
}

So the only thing I do is showing a messagebox as soon as the value
reaches 50.

When I increase the value of numericUpDown by clicking and holding the
mousebutton down for some seconds as soon as I reach the value 50 my
messagebox pops up (as expected), but then (after clicking ok on the
messagebox) I get a nullreferenceexception in:

Application.Run(new Form1());

This exception is NOT thrown when I try tho increase the value from 49
to 50 via one single mouse click. Just pressing and holding the
mousebutton to increase the value rapidly and "passing" the "critical
value" (50) causes this problem. It must be some timing issue within the
..net framework. Obviously a timer is used to increase the value
repeatedly while the mousebutton is pressed for some seconds.

Does anybody know this issue and how to avoid it?
Regards
Stephan

---------------------------------
System.NullReferenceException was unhandled
   Message="Object reference not set to an instance of an object."
   Source="System.Windows.Forms"
   StackTrace:
        at
System.Windows.Forms.UpDownBase.UpDownButtons.TimerHandler(Object
source, EventArgs args)
        at System.Windows.Forms.Timer.OnTick(EventArgs e)
        at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
        at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr
hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
        at
System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
        at
System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32
dwComponentID, Int32 reason, Int32 pvLoopData)
        at
System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32
reason, ApplicationContext context)
        at
System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32
reason, ApplicationContext context)
        at System.Windows.Forms.Application.Run(Form mainForm)
        at WindowsApplication1.Program.Main() in C:\Dokumente und
Einstellungen\Administrator\Eigene Dateien\Visual Studio
2005\Projects\WindowsApplication1\WindowsApplication1\Program.cs:line 17
        at System.AppDomain.nExecuteAssembly(Assembly assembly, String[]
args)
        at System.AppDomain.ExecuteAssembly(String assemblyFile,
Evidence assemblySecurity, String[] args)
        at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
        at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
        at System.Threading.ExecutionContext.Run(ExecutionContext
executionContext, ContextCallback callback, Object state)
        at System.Threading.ThreadHelper.ThreadStart()