Using Custom Editors

Most of the grid editors inherit from BaseVirtualGridEditor. The following steps and code snippet demonstrate how to replace the standard editor with a custom one containing a RadMultiColumnComboBoxElement:

1. Create a class that inherits BaseVirtualGridEditor.
2. Override its CreateEditorElement method and return a new instance of RadMultiColumnComboBoxElement.
3. Introduce DataSource, ValueMember, DisplayMember properties of the custom editor in order to data bind the editor element.
4. Override the Value property and manage the editor's value considering the RadMultiColumnComboBoxElement.SelectedValue property.
5. Subscribe to the RadVirtualGrid.EditorRequired event and replace the default editor for the desired column with your custom one.

Creating MultiColumnComboBoxVirtualGridEditor

public class MultiColumnComboBoxVirtualGridEditor : BaseVirtualGridEditor
{
    protected override Telerik.WinControls.RadElement CreateEditorElement()
    {
        return new RadMultiColumnComboBoxElement();
    }
    public override object Value
    {
        get
        {
            RadMultiColumnComboBoxElement editor = this.EditorElement as RadMultiColumnComboBoxElement;
            if (editor.SelectedValue != null)
            {
                if (!string.IsNullOrEmpty(editor.ValueMember))
                {
                    return editor.SelectedValue;
                }
            }
            return -1;
        }
        set
        {
            RadMultiColumnComboBoxElement editor = this.EditorElement as RadMultiColumnComboBoxElement;
            if (value == null)
            {
                editor.SelectedIndex = -1;
            }
            else if (editor.ValueMember != null)
            {
                editor.SelectedValue = value;
            }
        }
    }
    public object DataSource
    {
        get
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            return editorElement.DataSource;
        }
        set
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            if (editorElement.BindingContext == null)
            {
                editorElement.BindingContext = new BindingContext();
            }
            editorElement.DataSource = value;
        }
    }
    public string ValueMember
    {
        get
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            return editorElement.ValueMember;
        }
        set
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            editorElement.ValueMember = value;
        }
    }
    public string DisplayMember
    {
        get
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            return editorElement.DisplayMember;
        }
        set
        {
            RadMultiColumnComboBoxElement editorElement = this.EditorElement as RadMultiColumnComboBoxElement;
            editorElement.DisplayMember = value;
        }
    }
}
private void radVirtualGrid1_EditorRequired(object sender, Telerik.WinControls.UI.VirtualGridEditorRequiredEventArgs e)
{
    if (e.ColumnIndex == 2)
    {
        MultiColumnComboBoxVirtualGridEditor editor = new MultiColumnComboBoxVirtualGridEditor();
        DataTable dt = new DataTable();
        dt.Columns.Add("Id", typeof(int));
        dt.Columns.Add("Name", typeof(string));
        dt.Rows.Add(-1, "");
        for (int i = 0; i <= 9; i++)
        {
            dt.Rows.Add(i, "Item" + i);
        }
        editor.DataSource = dt;
        editor.ValueMember = "Id";
        editor.DisplayMember = "Name";
        e.Editor = editor;
    }
}

Public Class MultiColumnComboBoxVirtualGridEditor
    Inherits BaseVirtualGridEditor
    Protected Overrides Function CreateEditorElement() As Telerik.WinControls.RadElement
        Return New RadMultiColumnComboBoxElement()
    End Function
    Public Overrides Property Value() As Object
        Get
            Dim editor As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            If editor.SelectedValue IsNot Nothing Then
                If Not String.IsNullOrEmpty(editor.ValueMember) Then
                    Return editor.SelectedValue
                End If
            End If
            Return -1
        End Get
        Set(value As Object)
            Dim editor As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            If value Is Nothing Then
                editor.SelectedIndex = -1
            ElseIf editor.ValueMember IsNot Nothing Then
                editor.SelectedValue = value
            End If
        End Set
    End Property
    Public Property DataSource() As Object
        Get
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            Return editorElement.DataSource
        End Get
        Set(value As Object)
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            If editorElement.BindingContext Is Nothing Then
                editorElement.BindingContext = New BindingContext()
            End If
            editorElement.DataSource = value
        End Set
    End Property
    Public Property ValueMember() As String
        Get
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            Return editorElement.ValueMember
        End Get
        Set(value As String)
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            editorElement.ValueMember = value
        End Set
    End Property
    Public Property DisplayMember() As String
        Get
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            Return editorElement.DisplayMember
        End Get
        Set(value As String)
            Dim editorElement As RadMultiColumnComboBoxElement = TryCast(Me.EditorElement, RadMultiColumnComboBoxElement)
            editorElement.DisplayMember = value
        End Set
    End Property
End Class
Private Sub radVirtualGrid1_EditorRequired(sender As Object, e As Telerik.WinControls.UI.VirtualGridEditorRequiredEventArgs)
    If e.ColumnIndex = 2 Then
        Dim editor As New MultiColumnComboBoxVirtualGridEditor()
        Dim dt As New DataTable()
        dt.Columns.Add("Id", GetType(Integer))
        dt.Columns.Add("Name", GetType(String))
        dt.Rows.Add(-1, "")
        For i As Integer = 0 To 9
            dt.Rows.Add(i, "Item" & i)
        Next
        editor.DataSource = dt
        editor.ValueMember = "Id"
        editor.DisplayMember = "Name"
        e.Editor = editor
    End If
End Sub

See Also

Virtual grid editors