Collection Editor within a User Control at Design Time

Question

I have a UserControl class in a Windows Application project. One of the properties of it is a collection of another class that I have defined. I can't seem to find a good example of how to get the standard collection editor working for it at design time.

I got it working using some example code I found to a degree, but the data in my collection doesn't get saved. When I exit the form and open it back up in design time the data isn't there any more.

Here is my class:

Public Class Gauge
Inherits Control

Private WithEvents _Captions As New CaptionCollection

<Category("Gauge"), _
TypeConverter(GetType(CaptionCollectionConverter)), _
Description("Custom text displayed on the gauge.")> _
Public Property Captions() As CaptionCollection
 Get
  Return _Captions
 End Get
 Set(ByVal value As CaptionCollection)
  _Captions = value
 End Set
End Property

<Category("Gauge"), _
TypeConverter(GetType(CaptionConverter)), _
Description("Custom text displayed on the gauge.")> _
Public Class Caption
 Private _Text As String = ""
 Private _Color As Color = Color.Black
 Private _TextIsValue As Boolean
 Private _Position As New Point(0, 0)

 Public Property Text() As String
  Get
   Return _Text
  End Get
  Set(ByVal value As String)
   If _Text <> value Then
    _Text = value
   End If
  End Set
 End Property

 Public Property Color() As Color
  Get
   Return _Color
  End Get
  Set(ByVal value As Color)
   If _Color <> value Then
    _Color = value
   End If
  End Set
 End Property

 Public Property TextIsValue() As Boolean
  Get
   Return _TextIsValue
  End Get
  Set(ByVal value As Boolean)
   If _TextIsValue <> value Then
    _TextIsValue = value
   End If
  End Set
 End Property

 Public Property Position() As Point
  Get
   Return _Position
  End Get
  Set(ByVal value As Point)
   If _Position <> value Then
    _Position = value
   End If
  End Set
 End Property
End Class

Public Class CaptionCollection
 Inherits CollectionBase
 Implements ICustomTypeDescriptor

 Public Sub Add(ByVal c As Caption)
  Me.List.Add(c)
 End Sub

 Public Sub Remove(ByVal c As Caption)
  Me.List.Remove(c)
 End Sub

 Default Public ReadOnly Property Item(ByVal index As Integer) As Caption
  Get
   Return DirectCast(Me.List(index), Caption)
  End Get
 End Property

 ' Implementation of interface ICustomTypeDescriptor 
 Public Function GetClassName() As String Implements System.ComponentModel.ICustomTypeDescriptor.GetClassName
  Return TypeDescriptor.GetClassName(Me, True)
 End Function

 Public Function GetAttributes() As AttributeCollection Implements System.ComponentModel.ICustomTypeDescriptor.GetAttributes
  Return TypeDescriptor.GetAttributes(Me, True)
 End Function

 Public Function GetComponentName() As String Implements System.ComponentModel.ICustomTypeDescriptor.GetComponentName
  Return TypeDescriptor.GetComponentName(Me, True)
 End Function

 Public Function GetConverter() As TypeConverter Implements System.ComponentModel.ICustomTypeDescriptor.GetConverter
  Return TypeDescriptor.GetConverter(Me, True)
 End Function

 Public Function GetDefaultEvent() As EventDescriptor Implements System.ComponentModel.ICustomTypeDescriptor.GetDefaultEvent
  Return TypeDescriptor.GetDefaultEvent(Me, True)
 End Function

 Public Function GetDefaultProperty() As PropertyDescriptor Implements System.ComponentModel.ICustomTypeDescriptor.GetDefaultProperty
  Return TypeDescriptor.GetDefaultProperty(Me, True)
 End Function

 Public Function GetEditor(ByVal editorBaseType As Type) As Object Implements System.ComponentModel.ICustomTypeDescriptor.GetEditor
  Return TypeDescriptor.GetEditor(Me, editorBaseType, True)
 End Function

 Public Function GetEvents(ByVal attributes As Attribute()) As EventDescriptorCollection Implements System.ComponentModel.ICustomTypeDescriptor.GetEvents
  Return TypeDescriptor.GetEvents(Me, attributes, True)
 End Function

 Public Function GetEvents() As EventDescriptorCollection Implements System.ComponentModel.ICustomTypeDescriptor.GetEvents
  Return TypeDescriptor.GetEvents(Me, True)
 End Function

 Public Function GetPropertyOwner(ByVal pd As PropertyDescriptor) As Object Implements System.ComponentModel.ICustomTypeDescriptor.GetPropertyOwner
  Return Me
 End Function

 Public Function GetProperties(ByVal attributes As Attribute()) As PropertyDescriptorCollection Implements System.ComponentModel.ICustomTypeDescriptor.GetProperties
  Return GetProperties()
 End Function

 Public Function GetProperties() As PropertyDescriptorCollection Implements System.ComponentModel.ICustomTypeDescriptor.GetProperties
  ' Create a collection object to hold property descriptors
  Dim pds As New PropertyDescriptorCollection(Nothing)

  ' Iterate the list of employees
  For i As Integer = 0 To Me.List.Count - 1
   ' Create a property descriptor for the caption item and add to the property descriptor collection
   Dim pd As New CaptionCollectionPropertyDescriptor(Me, i)
   pds.Add(pd)
  Next
  ' return the property descriptor collection
  Return pds
 End Function
End Class

' This is a special type converter which will be associated with the Caption class.
' It converts a Caption object to string representation for use in a property grid.
Friend Class CaptionConverter
 Inherits ExpandableObjectConverter

 Public Overloads Overrides Function ConvertTo(ByVal context As ITypeDescriptorContext, ByVal culture As System.Globalization.CultureInfo, ByVal value As Object, ByVal destType As Type) As Object
  'Return "(Collection)"
  If destType Is GetType(String) AndAlso TypeOf value Is Caption Then
   ' Cast the value to an Caption type
   Dim emp As Caption = DirectCast(value, Caption)
   ' Return the text for display.
   Return emp.Text
  End If
  Return MyBase.ConvertTo(context, culture, value, destType)
 End Function
End Class

' This is a special type converter which will be associated with the CaptionCollection class.
' It converts a CaptionCollection object to a string representation for use in a property grid.
Friend Class CaptionCollectionConverter
 Inherits ExpandableObjectConverter

 Public Overloads Overrides Function ConvertTo(ByVal context As ITypeDescriptorContext, ByVal culture As System.Globalization.CultureInfo, ByVal value As Object, ByVal destType As Type) As Object
  If destType Is GetType(String) AndAlso TypeOf value Is CaptionCollection Then
   ' Return department and department role separated by comma.
   Return "(Collection)"
  End If
  Return MyBase.ConvertTo(context, culture, value, destType)
 End Function
End Class

Public Class CaptionCollectionPropertyDescriptor
 Inherits PropertyDescriptor
 Private collection As CaptionCollection = Nothing
 Private index As Integer = -1

 Public Sub New(ByVal coll As CaptionCollection, ByVal idx As Integer)
  MyBase.New("#" & idx.ToString(), Nothing)
  Me.collection = coll
  Me.index = idx
 End Sub

 Public Overloads Overrides ReadOnly Property Attributes() As AttributeCollection
  Get
   Return New AttributeCollection(Nothing)
  End Get
 End Property

 Public Overloads Overrides Function CanResetValue(ByVal component As Object) As Boolean
  Return True
 End Function

 Public Overloads Overrides ReadOnly Property ComponentType() As Type
  Get
   Return Me.collection.[GetType]()
  End Get
 End Property

 Public Overloads Overrides ReadOnly Property DisplayName() As String
  Get
   Return "Caption" + (index + 1).ToString()
  End Get
 End Property

 Public Overloads Overrides ReadOnly Property Description() As String
  Get
   Return "Caption" + (index + 1).ToString()
  End Get
 End Property

 Public Overloads Overrides Function GetValue(ByVal component As Object) As Object
  Return Me.collection(index)
 End Function

 Public Overloads Overrides ReadOnly Property IsReadOnly() As Boolean
  Get
   Return False
  End Get
 End Property

 Public Overloads Overrides ReadOnly Property Name() As String
  Get
   Return "#" & index.ToString()
  End Get
 End Property

 Public Overloads Overrides ReadOnly Property PropertyType() As Type
  Get
   Return Me.collection(index).[GetType]()
  End Get
 End Property

 Public Overloads Overrides Sub ResetValue(ByVal component As Object)
 End Sub

 Public Overloads Overrides Function ShouldSerializeValue(ByVal component As Object) As Boolean
  Return True
 End Function

 Public Overloads Overrides Sub SetValue(ByVal component As Object, ByVal value As Object)
  ' this.collection[index] = value;
 End Sub
End Class

End Class

Answer 1

I found my answer. The thing I was missing was this attribute in the Captions property: DesignerSerializationVisibility(DesignerSerializationVisibility.Content