Attach Event for Editor Changes

There is no default event for editor changes in grid columns - it is up to the developer to attach events to these editors when necessary. This operation can be performed hooking the ItemCreated event of Telerik RadGrid. For example- in case with GridDropDownColumn you have to:

1. Check whether the currently created grid item is GridDataItem and is in edit mode

2. Locate the dropdown list editor in the Controls collection of the cell which corresponds to the GridDropDownList column

3. Mark it with AutoPostBack = true and wire a handler to its SelectedIndexChanged event. Then in the SelectedIndexChanged handler you can update the selected value for the second dropdown.

<telerik:RadGrid RenderMode="Lightweight" ID="RadGrid1" runat="server">
  <MasterTableView EditMode="InPlace" AutoGenerateColumns="False">
    <Columns>
      <telerik:GridBoundColumn HeaderText="CustomerID" DataField="CustomerID" UniqueName="CustomerID">
      </telerik:GridBoundColumn>
      <telerik:GridDropDownColumn HeaderText="ContactName" ListDataMember="Customers" ListTextField="ContactName"
        DataField="CustomerID" UniqueName="DropDownColumn1" ListValueField="CustomerID">
      </telerik:GridDropDownColumn>
      <telerik:GridDropDownColumn HeaderText="ContactTitle" ListDataMember="Customers"
        ListTextField="ContactTitle" DataField="CustomerID" UniqueName="DropDownColumn2"
        ListValueField="CustomerID">
      </telerik:GridDropDownColumn>
      <telerik:GridEditCommandColumn UniqueName="EditCommandColumn">
      </telerik:GridEditCommandColumn>
    </Columns>
  </MasterTableView>
</telerik:RadGrid>

Private Sub RadGrid1_ItemCreated(ByVal sender As Object, ByVal e As Telerik.Web.UI.GridItemEventArgs) Handles RadGrid1.ItemCreated
    If (TypeOf e.Item Is GridEditableItem AndAlso e.Item.IsInEditMode) Then
        Dim list As DropDownList =
        CType(CType(e.Item, GridEditableItem)("DropDownColumn1").Controls(0),
        DropDownList)
        list.AutoPostBack = True
        AddHandler list.SelectedIndexChanged, AddressOf list_SelectedIndexChanged
    End If
End Sub
Private Sub list_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
    'change the selected value for ContactTitle here
End Sub

private void RadGrid1_ItemCreated(object sender, Telerik.Web.UI.GridItemEventArgs e)
{
    if (e.Item is GridEditableItem && e.Item.IsInEditMode)
    {
        DropDownList list = (e.Item as GridEditableItem)["DropDownColumn1"].Controls[0] as DropDownList;
        list.AutoPostBack = true;
        list.SelectedIndexChanged += new System.EventHandler(this.list_SelectedIndexChanged);
    }
}

private void list_SelectedIndexChanged(object sender, System.EventArgs e)
{
    // change the selected value for ContactTitle here
}