Custom property editor (UITypeEditor) not working properly with class

[NickThissen]

Hi,


I want to give some property of a custom control I created a custom property editor window. What I mean by that is that, in the property grid, the property is not directly editable but has a "[...]" button next to it. Clicking that button will open an editor form which allows you to edit the value.


In the screenshot you can see a very simple example, where 'MyProperty' is just a String property on a custom TextBox class:

Imports System.ComponentModel
Imports System.Drawing.Design
 
Public Class CustomTextBox
    Inherits TextBox
 
    Private _MyProperty As String
    <Editor(GetType(CustomPropertyEditor), GetType(UITypeEditor))> _
    Public Property MyProperty() As String
        Get
            Return _MyProperty
        End Get
        Set(ByVal value As String)
            _MyProperty = value
        End Set
    End Property
 
End Class

The CustomPropertyEditor class, which is set as this property's EditorAttribute, is slightly involved, so I left out some of the irrelevant parts. It inherits from UITypeEditor and takes care of showing a modal form when the [...] button is clicked.

Imports System.Drawing
Imports System.Drawing.Design
Imports System.Windows.Forms
Imports System.Windows.Forms.Design
Imports System.ComponentModel
 
Public Class CustomPropertyEditor
    Inherits System.Drawing.Design.UITypeEditor
 
    Private m_editorForm As TextEditorForm
 
    Private Function GetEditControl(ByVal PropertyName As String, ByVal CurrentValue As Object) As System.Windows.Forms.Control
        Dim str As String = CStr(CurrentValue)
        m_editorForm = New TextEditorForm()
        m_editorForm.Value = str
        Return m_editorForm
    End Function
 
    Private Function GetEditedValue(ByVal EditControl As System.Windows.Forms.Control, ByVal PropertyName As String, ByVal OldValue As Object) As Object
        If m_editorForm Is Nothing _
        OrElse m_editorForm.DialogResult = DialogResult.Cancel Then
            Return OldValue
        Else
            Return m_editorForm.Value
        End If
    End Function
 
    Public Overrides Function GetEditStyle(ByVal context As System.ComponentModel.ITypeDescriptorContext) As UITypeEditorEditStyle
        Return UITypeEditorEditStyle.Modal
    End Function
 
    'some stuff omitted
 
End Class

Basically, the GetEditorControl function returns a new instance of the TextEditorForm (which is the modal form you can see on the screenshot, used to edit the property), but first sets its Value property (the text in its TextBox) to the current value of the MyProperty property.
The GetEditedValue function is used to return the result of the edit (the text in the textbox, which is the Value property) back to the property.


This works just fine. I can edit the String property and the result is stored and shown forever. Great.


Then, I wanted something more involved. Instead of just a String property, I have a property that returns an instance of some nested class, which in turn carries a whole load of other properties.

So now the CustomTextbox class becomes a little more involved. It has one nested class (called NestedClass), with two string properties (as an example). It exposes an instance of this class via a NestedClassInstance property.

Imports System.ComponentModel
Imports System.Drawing.Design
 
Public Class CustomTextBox
    Inherits TextBox
 
    Public Sub New()
        _NestedClassInstance = New NestedClass()
    End Sub
 
    Private _NestedClassInstance As NestedClass
    <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
    <Editor(GetType(CustomPropertyEditor), GetType(UITypeEditor))> _
    Public Property NestedClassInstance() As NestedClass
        Get
            Return _NestedClassInstance
        End Get
        Set(ByVal value As NestedClass)
            _NestedClassInstance = value
        End Set
    End Property
 
    Public Class NestedClass
 
        Private _MyProperty1 As String
        Public Property MyProperty1() As String
            Get
                Return _MyProperty1
            End Get
            Set(ByVal value As String)
                _MyProperty1 = value
            End Set
        End Property
 
        Private _MyProperty2 As String
        Public Property MyProperty2() As String
            Get
                Return _MyProperty2
            End Get
            Set(ByVal value As String)
                _MyProperty2 = value
            End Set
        End Property
    End Class
 
End Class

This time, the Editor attribute is set on the NestedClassInstance property, because I want to edit that property directly via the editor form.

(Please note that, if I get rid of the Editor attribute, and replace it with an ExpandableObject TypeConverter attribute, (so that the property is expandable in the property grid), I can get and set the two string properties just fine, simply using the property grid, and they are stored like they should be.)


Now, in order for my editor form to be able to change this NestedClassInstance property, I gave it a PropertyGrid control instead of the TextBox. I also had it take an instance of the CustomTextBox.NestedClass in its constructor, so that the PropertyGrids SelectedObject can be set to that instance, so that it's editable. Finally, there is now a NestedClassInstance on the editor form as well, which simply returns the instance of the NestedClass which was passed again.

Imports System.Windows.Forms
 
Public Class TextEditorForm
 
    Private _NestedClassInstance As CustomTextBox.NestedClass
    Public Sub New(ByVal nc As CustomTextBox.NestedClass)
 
        ' This call is required by the Windows Form Designer.
        InitializeComponent()
 
        ' Add any initialization after the InitializeComponent() call.
        _NestedClassInstance = nc
        PropertyGrid1.SelectedObject = nc
    End Sub
 
    Public ReadOnly Property NestedClassInstance() As CustomTextBox.NestedClass
        Get
            Return _NestedClassInstance
        End Get
    End Property
 
    Private Sub OK_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK_Button.Click
        Me.DialogResult = System.Windows.Forms.DialogResult.OK
        Me.Close()
    End Sub
 
    Private Sub Cancel_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cancel_Button.Click
        Me.DialogResult = System.Windows.Forms.DialogResult.Cancel
        Me.Close()
    End Sub
 
End Class

Simple enough I hope.


Now finally, I also needed a slight change in the CustomPropertyEditor UITypeEditor, mainly just to pass the CurrentValue (cast to a NestedClass class) to the editor form, and to get it back again:

Imports System.Drawing
Imports System.Drawing.Design
Imports System.Windows.Forms
Imports System.Windows.Forms.Design
Imports System.ComponentModel
 
Public Class CustomPropertyEditor
    Inherits System.Drawing.Design.UITypeEditor
 
    Private m_editorForm As TextEditorForm
 
    Private Function GetEditControl(ByVal PropertyName As String, ByVal CurrentValue As Object) As System.Windows.Forms.Control
        Dim nestedClass = TryCast(CurrentValue, CustomTextBox.NestedClass)
        If nestedClass IsNot Nothing Then
            m_editorForm = New TextEditorForm(nestedClass)
            Return m_editorForm
        Else
            Return Nothing
        End If
    End Function
 
    Private Function GetEditedValue(ByVal EditControl As System.Windows.Forms.Control, ByVal PropertyName As String, ByVal OldValue As Object) As Object
        If m_editorForm Is Nothing _
        OrElse m_editorForm.DialogResult = DialogResult.Cancel Then
            Return OldValue
        Else
            Return m_editorForm.NestedClassInstance
        End If
    End Function
 
    Public Overrides Function GetEditStyle(ByVal context As System.ComponentModel.ITypeDescriptorContext) As UITypeEditorEditStyle
        Return UITypeEditorEditStyle.Modal
    End Function
 
End Class

Now when I click the button in the property grid, I get the new editor form with PropertyGrid control, which shows my two properties:


So far so good. I can change the properties on the editor form, press the OK button, and they seem to be stored. When I open the editor form again, the changes were persisted.

However...

When I build the solution, close the Form1 designer file, and then re-open it (so that it's reloaded), then the changes are gone! It seems they are not persisted after all, at least not in the form designer file I guess.

Also, when I make a change, Visual Studio doesn't seem to 'notice' it, as it does not tell me that the Form1.vb file has changed, so I can't even save it before closing it. (It doesn't get the asterisk * after it's name indicating an unsaved change).

As I said before: if I get rid of the whole custom UITypeEditor thingy, and just edit the properties from the property grid, it works fine. Then the changes are persisted even after building.


Am I missing something? Am I doing something fundamentally wrong? I can't really see the difference in using a String as the type to edit, or some custom class which in turn hosts some other properties. A String is just another class, right? So where's the difference?

Note also that I am already setting the DesignerSerializationVisibility attribute of the NestedClassInstance to Content, which, in my understanding, should ensure that any changes to that property are stored in the designer file. Still, it doesn't work.


Anyone? Thanks for any help!