I am currently completely puzzled by the problem I am facing. I am writing a plugin for another application that provides an open .NET API. I created a class with the name Room, and I use PropertyGrid so that users can see and edit the properties of instances Room. Several properties are limited to a set of standard values. Thus, I use custom TypeDescriptors with overrides GetStandardValues()to get a property grid to display a drop-down list for these properties.
It was all beautiful. I was getting a drop and I could edit the values without a problem. However, now for some reason, when I select Room, the PropertyGrid shows properties with type descriptors like a black box.
If I click on the field, it will turn white and I will get a blinking cursor, but I can not print anything. If I then select another room, my program will fail with the following exception:
System.InvalidCastException was caught
Message=Unable to cast object of type 'DVAMC.Room' to type 'DVAMC.Room'.
Source=DVAMC
StackTrace:
at DVAMC.BuildingTypeConverter.GetStandardValuesSupported(ITypeDescriptorContext context) in C:\Documents and Settings\eric.anastas\My Documents\_SVN WC\DVAMC Working\BuildingTypeConverter.cs:line 14
at System.Windows.Forms.PropertyGridInternal.GridEntry.get_Flags()
at System.Windows.Forms.PropertyGridInternal.GridEntry.get_NeedsDropDownButton()
at System.Windows.Forms.PropertyGridInternal.PropertyDescriptorGridEntry.get_NeedsDropDownButton()
at System.Windows.Forms.PropertyGridInternal.PropertyGridView.SelectRow(Int32 row)
at System.Windows.Forms.PropertyGridInternal.PropertyGridView.SelectGridEntry(GridEntry gridEntry, Boolean fPageIn)
at System.Windows.Forms.PropertyGridInternal.PropertyGridView.GridPositionData.Restore(PropertyGridView gridView)
at System.Windows.Forms.PropertyGridInternal.PropertyGridView.Refresh(Boolean fullRefresh, Int32 rowStart, Int32 rowEnd)
at System.Windows.Forms.PropertyGridInternal.PropertyGridView.Refresh()
at System.Windows.Forms.PropertyGrid.Refresh(Boolean clearCached)
at System.Windows.Forms.PropertyGrid.set_SelectedObjects(Object[] value)
at System.Windows.Forms.PropertyGrid.set_SelectedObject(Object value)
at DVAMC.RoomDetailsForm.set_RoomDetailsSelectedRoom(Room value) in C:\Documents and Settings\eric.anastas\My Documents\_SVN WC\DVAMC Working\RoomDetailsForm.cs:line 115
at DVAMC.RoomDetailsForm.roomListTreeView_SelectionChanged(Object sender, EventArgs e) in C:\Documents and Settings\eric.anastas\My Documents\_SVN WC\DVAMC Working\RoomDetailsForm.cs:line 159
at BrightIdeasSoftware.ObjectListView.OnSelectionChanged(EventArgs e)
at BrightIdeasSoftware.ObjectListView.HandleApplicationIdle(Object sender, EventArgs e)
at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle(Int32 grfidlef)
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.RunDialog(Form form)
at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
at System.Windows.Forms.Form.ShowDialog()
at DVAMC.RoomDetailsCmd.Execute(ExternalCommandData commandData, String& message, ElementSet elements) in C:\Documents and Settings\eric.anastas\My Documents\_SVN WC\DVAMC Working\RoomDetailsCmd.cs:line 44
InnerException:
The last item in the stack trace points to my BuildingTypeConverter.GetStandardValuesSupported () method, which is shown below.
GetStandardValuesSupported(System.ComponentModel.ITypeDescriptorContext context)
{
Room r = (Room)context.Instance; //this is line 14 referenced by the InvalidCastException stack trace
if (r.IsLinked)
{
return true;
}
else
{
return false;
}
}
, 14 , . , , InvalidCastException , , GetStandardValues () , . , .
public override bool GetStandardValuesSupported(System.ComponentModel.ITypeDescriptorContext context)
{
string s = "hello world";
int i = 0;
Room r = (Room)context.Instance;
.....
InvalidCastException. , string s. , , .
, , . SVN. , , InvalidCastExceptions. - , ?