Dynamic TypeConverter

[shersu]

Hi,

I have a combo box and a property grid in a form. The combo box contains 2 items. If one item is selected, two properties are listed in the property grid. These properties should have a dropdown that contains a list of items. I have two string arrays that contain the values for these properties. Can I use one TypeConverter that inherits StringConverter for these lists to be displayed in two different properties? That is, with one TypeConverter class, can I populate both the lists? I will also have to do the same with the other items in the combo box.

Thanks

[.paul.]

can you explain exactly how you expect this to work?
i'm sure there's a simple solution, but your question is unclear

[ForumAccount]

Yes it is possible, as for whether it is the best practice, I would say no. You should be creating a new TypeConverter for each property. However, here is how you can do it. Drag a ComboBox and PropertyGrid onto your Form and use the following code:

Imports System.ComponentModel

Public Class Form1

    '//methods
    Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
        MyBase.OnLoad(e)

        '//add the two types
        Me.ComboBox1.Items.Add(GetType(Item1))
        Me.ComboBox1.Items.Add(GetType(Item2))

        '//display the type names
        Me.ComboBox1.DisplayMember = "Name"

    End Sub

    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) _
                                               Handles ComboBox1.SelectedIndexChanged
        Dim item = Me.ComboBox1.SelectedItem
        If item IsNot Nothing Then
            Dim type = DirectCast(item, Type)
            '//bind a new instance of that type to the property grid
            Me.PropertyGrid1.SelectedObject = Activator.CreateInstance(type, False)
        End If
    End Sub

End Class

Public Class Item1

    Private _name As String
    <TypeConverter(GetType(DynamicItemConverter))> _
    Public Property Name As String
        Get
            Return Me._name
        End Get
        Set(ByVal value As String)
            Me._name = value
        End Set
    End Property

    Private _country As String
    <TypeConverter(GetType(DynamicItemConverter))> _
    Public Property Country As String
        Get
            Return Me._country
        End Get
        Set(ByVal value As String)
            Me._country = value
        End Set
    End Property

End Class

Public Class Item2

    Private _address As String
    <TypeConverter(GetType(DynamicItemConverter))> _
    Public Property Address As String
        Get
            Return Me._address
        End Get
        Set(ByVal value As String)
            Me._address = value
        End Set
    End Property

End Class

Public Class DynamicItemConverter
    Inherits TypeConverter

    '//methods
    Public Overrides Function GetStandardValues _
            (ByVal context As ITypeDescriptorContext) As StandardValuesCollection

        If context IsNot Nothing Then
            If context.Instance IsNot Nothing Then
                If context.PropertyDescriptor IsNot Nothing Then
                    Select Case True
                        Case TypeOf context.Instance Is Item1
                            Select Case context.PropertyDescriptor.Name

                                '//corresponds to the property name of the type
                                Case "Name"
                                    Return New StandardValuesCollection({"John Smith", _
                                                                         "Jane Smith"})
                                Case "Country"
                                    Return New StandardValuesCollection({"Europe", _
                                                                         "Canada", _
                                                                         "USA"})
                            End Select

                        Case TypeOf context.Instance Is Item2
                            Select Case context.PropertyDescriptor.Name
                                Case "Address"
                                    Return New StandardValuesCollection({"123 Some Street", _
                                                                         "456 Some Avenue"})
                            End Select
                    End Select
                End If
            End If
        End If

        '//always call the base implementation
        Return MyBase.GetStandardValues(context)
    End Function

    Public Overrides Function GetStandardValuesSupported _
            (ByVal context As ITypeDescriptorContext) As Boolean

        '//yes, we can supply values for the property grid
        Return True
    End Function

End Class