title: Collection Editor within a User Control at Design Time
body: <p>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.</p>
  
  <p>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.</p>
  
  <p>Here is my class:</p>
  
  <pre><code>Public Class Gauge
  Inherits Control
  
  Private WithEvents _Captions As New CaptionCollection
  
  &lt;Category("Gauge"), _
  TypeConverter(GetType(CaptionCollectionConverter)), _
  Description("Custom text displayed on the gauge.")&gt; _
  Public Property Captions() As CaptionCollection
      Get
          Return _Captions
      End Get
      Set(ByVal value As CaptionCollection)
          _Captions = value
      End Set
  End Property
  
  &lt;Category("Gauge"), _
  TypeConverter(GetType(CaptionConverter)), _
  Description("Custom text displayed on the gauge.")&gt; _
  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 &lt;&gt; 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 &lt;&gt; 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 &lt;&gt; 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 &lt;&gt; 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("#" &amp; 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 "#" &amp; 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
  </code></pre>
  
  <p>End Class</p>