Getting the assembly a control is being used in, from a custom UITypeEditor, at design time - uitypeeditor

Question

Although there are many threads dealing with similar questions I couldn't find any that cover this case.
I have a main app that references a class library. In the class library is a control with a property that must be populated with a form name from a drop-down of forms available in the main app - NOT the class library.
I've discovered that, inside of the UITypeEditor code,
Control owner = context.Instance as Control;
gives me a reference to the control for which the property value is required. But getting a reference to the proper assembly (the main app, not the library the control is in) so that I can list the available form names in a drop down has proved difficult.
owner.GetType().Assembly.ToString() -- gives me the class library name, not the main app
Assembly.GetExecutingAssembly().ToString() --- gives me the class library name
Assembly.GetCallingAssembly().ToString() --- gives me System.Windows.Forms
There is no route I can find to getting the assembly of the form onto which I'm placing the control which has the property with custom editor that needs that assembly.

Answer 1

I realize this is an old question, but it is easily answered if one understands the mechanisms employed in writing basic designer code. There are three articles that I recommend reading to gain a working knowledge of the subject.
Building Windows Forms Controls and Components with Rich Design-Time Features; MSDN Magazine, April 2003
Building Windows Forms Controls and Components with Rich Design-Time Features, Part 2; MSDN Magazine, May 2003
Tailor Your Application by Building a Custom Forms Designer with .NET; MSDN Magazine, December 2004
Note: The above links are to compiled HTML help files. Remember to unblock the content using the file's properties dialog.
To obtain a reference to the Assembly that contains the Form with the Control being manipulated on the design surface, you need to obtain a reference to the IDesignerHost service from the IServiceProvider instance "provider" that is passed the EditValue method. IDesignerHost exposes the property RootComponentClassName that will be the fully qualified name of the base component class which in this case is the containing form. With this name you can obtain a Type instance using the IDesignerHost.GetType method. Note that GetType may return a null value if the project has not been "built" since adding the form to the project.
C# Example Snippet For UITypeEditor
public override object EditValue(System.ComponentModel.ITypeDescriptorContext context, IServiceProvider provider, object value)
{
IDesignerHost host = provider.GetService(typeof(IDesignerHost)) as IDesignerHost;
string typName = host.RootComponentClassName;
Type typ = host.GetType(typName);
Assembly asm = null;
if (typ == null)
{
MessageBox.Show("Please build project before attempting to set this property");
return base.EditValue(context, provider, value);
}
else
{
asm = typ.Assembly;
}
// ... remaining code
return base.EditValue(context, provider, value);
}
VB Example Snippet For UITypeEditor
Public Overrides Function EditValue(context As ITypeDescriptorContext, provider As IServiceProvider, value As Object) As Object
Dim host As IDesignerHost = TryCast(provider.GetService(GetType(IDesignerHost)), IDesignerHost)
Dim typName As String = host.RootComponentClassName
Dim typ As Type = host.GetType(typName)
Dim asm As Assembly
If typ Is Nothing Then
MessageBox.Show("Please build project before attempting to set this property")
Return MyBase.EditValue(context, provider, value)
Else
asm = typ.Assembly
End If
' ... remaining code
Return MyBase.EditValue(context, provider, value)
End Function