How to use RadDropDownList as editor in RadPropertyGrid

Environment

Product Version	Product	Author
2019.1.219	RadPropertyGrid for WinForms	Dimitar Karamfilov

Description

You want to use RadDropDownList as editor for a specific property in RadPropertyGrid. In addition the a proper value should be displayed when the user is not editing as well. The below image shows how this will look when ready.

Solution

There a built-in editor that can be used for this PropertyGridDropDownListEditor but this editor is not used by for the standard types. First you need to use the EditorRequired event to change the editor. Then you can use the EditorInitialized event to set the data source. The final step is to format the when not in edit mode and the drop down list is not visible. The following snippet a complete example for this:

public partial class RadForm1 : Telerik.WinControls.UI.RadForm
{
    DataTable table = GetTable();
    public RadForm1()
    {
        InitializeComponent();
        new RadControlSpyForm().Show();
        PropertyStoreItem intItem = new PropertyStoreItem(typeof(int), "Id", 1);

        RadPropertyStore store = new RadPropertyStore();
        store.Add(intItem);

        this.radPropertyGrid1.SelectedObject = store;

        radPropertyGrid1.EditorRequired += RadPropertyGrid1_EditorRequired;
        radPropertyGrid1.EditorInitialized += RadPropertyGrid1_EditorInitialized;
        radPropertyGrid1.ItemFormatting += RadPropertyGrid1_ItemFormatting;
    }

    private void RadPropertyGrid1_ItemFormatting(object sender, PropertyGridItemFormattingEventArgs e)
    {
        if (e.Item.Name == "Id")
        {
            var visualItem = e.VisualElement as PropertyGridItemElement;
            var valueElememt = visualItem.ValueElement;
            var value = (int)(visualItem.Data as PropertyGridItem).Value;
            valueElememt.Text = GetValueById(value, "Id", "Name");
        }

    }

    private string GetValueById(int value, string valueMember, string displayMember)
    {
        for (int i = 0; i < table.Rows.Count; i++)
        {
            var row = table.Rows[i];
            if (value.Equals(row[valueMember]))
            {
                return row[displayMember].ToString();
            }
        }
        return string.Empty;
    }
    private void RadPropertyGrid1_EditorInitialized(object sender, PropertyGridItemEditorInitializedEventArgs e)
    {
        if (e.Item.Name == "Id")
        {
            var editor = e.Editor as PropertyGridDropDownListEditor;
            var element = editor.EditorElement as BaseDropDownListEditorElement;
            element.DisplayMember = "Name";
            element.ValueMember = "Id";
            element.DataSource = GetTable();
        }
    }
    private void RadPropertyGrid1_EditorRequired(object sender, PropertyGridEditorRequiredEventArgs e)
    {
        if (e.Item.Name == "Id")
        {
            e.EditorType = typeof(PropertyGridDropDownListEditor);
        }
    }
    static DataTable GetTable()
    {
        DataTable table = new DataTable();
        table.Columns.Add("Id", typeof(int));
        table.Columns.Add("Name", typeof(string)); 

        table.Rows.Add(1, "David");
        table.Rows.Add(2, "Sam");
        table.Rows.Add(3, "Christoff");
        table.Rows.Add(4, "Janet");
        table.Rows.Add(5, "Melanie");
        return table;
    }
}

Partial Public Class RadForm1
    Inherits Telerik.WinControls.UI.RadForm

    Private table As DataTable = GetTable()
    Public Sub New()
        InitializeComponent()
        Call (New RadControlSpyForm()).Show()
        Dim intItem As New PropertyStoreItem(GetType(Integer), "Id", 1)

        Dim store As New RadPropertyStore()
        store.Add(intItem)

        Me.radPropertyGrid1.SelectedObject = store

        AddHandler radPropertyGrid1.EditorRequired, AddressOf RadPropertyGrid1_EditorRequired
        AddHandler radPropertyGrid1.EditorInitialized, AddressOf RadPropertyGrid1_EditorInitialized
        AddHandler radPropertyGrid1.ItemFormatting, AddressOf RadPropertyGrid1_ItemFormatting
    End Sub

    Private Sub RadPropertyGrid1_ItemFormatting(ByVal sender As Object, ByVal e As PropertyGridItemFormattingEventArgs)
        If e.Item.Name = "Id" Then
            Dim visualItem = TryCast(e.VisualElement, PropertyGridItemElement)
            Dim valueElememt = visualItem.ValueElement
            Dim value = CInt(Math.Truncate((TryCast(visualItem.Data, PropertyGridItem)).Value))
            valueElememt.Text = GetValueById(value, "Id", "Name")
        End If

    End Sub

    Private Function GetValueById(ByVal value As Integer, ByVal valueMember As String, ByVal displayMember As String) As String
        For i As Integer = 0 To table.Rows.Count - 1
            Dim row = table.Rows(i)
            If value.Equals(row(valueMember)) Then
                Return row(displayMember).ToString()
            End If
        Next i
        Return String.Empty
    End Function
    Private Sub RadPropertyGrid1_EditorInitialized(ByVal sender As Object, ByVal e As PropertyGridItemEditorInitializedEventArgs)
        If e.Item.Name = "Id" Then
            Dim editor = TryCast(e.Editor, PropertyGridDropDownListEditor)
            Dim element = TryCast(editor.EditorElement, BaseDropDownListEditorElement)
            element.DisplayMember = "Name"
            element.ValueMember = "Id"
            element.DataSource = GetTable()
        End If
    End Sub
    Private Sub RadPropertyGrid1_EditorRequired(ByVal sender As Object, ByVal e As PropertyGridEditorRequiredEventArgs)
        If e.Item.Name = "Id" Then
            e.EditorType = GetType(PropertyGridDropDownListEditor)
        End If
    End Sub
    Private Shared Function GetTable() As DataTable
        Dim table As New DataTable()
        table.Columns.Add("Id", GetType(Integer))
        table.Columns.Add("Name", GetType(String))

        table.Rows.Add(1, "David")
        table.Rows.Add(2, "Sam")
        table.Rows.Add(3, "Christoff")
        table.Rows.Add(4, "Janet")
        table.Rows.Add(5, "Melanie")
        Return table
    End Function
End Class