<telerik:GridTemplateColumn HeaderText="VENDOR NAME" Visible="false" SortExpression="VENDOR_DESCR" UniqueName="VENDOR_ID">
    <ItemTemplate>
        <%# Eval("ShipCountry")%>
    </ItemTemplate>
    <EditItemTemplate>
        <telerik:RadDropDownList ID="rddl_Vendors" runat="server"
            OnDataBinding="rddl_Vendors_DataBinding"
            SelectedText='<%# Bind("ShipCountry") %>'
            DataTextField="ShipCountry"
            DataValueField="OrderID">
        </telerik:RadDropDownList>
    </EditItemTemplate>
</telerik:GridTemplateColumn>

<asp:Label ID="Label1" runat="server" Text="Action:"></asp:Label>
<telerik:RadGrid ID="RadGrid1" runat="server" AllowPaging="True" Width="800px"
    AutoGenerateEditColumn="true"
    AutoGenerateDeleteColumn="true"
    OnNeedDataSource="RadGrid1_NeedDataSource"
    OnInsertCommand="RadGrid1_InsertCommand"
    OnUpdateCommand="RadGrid1_UpdateCommand"
    OnDeleteCommand="RadGrid1_DeleteCommand">

    <MasterTableView AutoGenerateColumns="False" DataKeyNames="OrderID" CommandItemDisplay="Top" InsertItemDisplay="Top" InsertItemPageIndexAction="ShowItemOnLastPage">
        <Columns>
            <telerik:GridBoundColumn DataField="OrderID" DataType="System.Int32"
                FilterControlAltText="Filter OrderID column" HeaderText="OrderID"
                ReadOnly="True" SortExpression="OrderID" UniqueName="OrderID">
            </telerik:GridBoundColumn>
            <telerik:GridDateTimeColumn DataField="OrderDate" DataType="System.DateTime"
                FilterControlAltText="Filter OrderDate column" HeaderText="OrderDate"
                SortExpression="OrderDate" UniqueName="OrderDate">
            </telerik:GridDateTimeColumn>
            <telerik:GridNumericColumn DataField="Freight" DataType="System.Decimal"
                FilterControlAltText="Filter Freight column" HeaderText="Freight"
                SortExpression="Freight" UniqueName="Freight">
            </telerik:GridNumericColumn>
            <telerik:GridBoundColumn DataField="ShipName"
                FilterControlAltText="Filter ShipName column" HeaderText="ShipName"
                SortExpression="ShipName" UniqueName="ShipName">
            </telerik:GridBoundColumn>
            <telerik:GridBoundColumn DataField="ShipCountry" ReadOnly="true"
                FilterControlAltText="Filter ShipCountry column" HeaderText="ShipCountry"
                SortExpression="ShipCountry" UniqueName="ShipCountry">
            </telerik:GridBoundColumn>
            <telerik:GridTemplateColumn HeaderText="VENDOR NAME" Visible="false" SortExpression="VENDOR_DESCR" UniqueName="VENDOR_ID">
                <ItemTemplate>
                    <%# Eval("ShipCountry")%>
                </ItemTemplate>
                <EditItemTemplate>
                    <telerik:RadDropDownList ID="rddl_Vendors" runat="server"
                        OnDataBinding="rddl_Vendors_DataBinding"
                        SelectedText='<%# Bind("ShipCountry") %>'
                        DataTextField="ShipCountry"
                        DataValueField="OrderID">
                    </telerik:RadDropDownList>
                </EditItemTemplate>
            </telerik:GridTemplateColumn>
        </Columns>
    </MasterTableView>
</telerik:RadGrid>

#region Properties for CRUD Operations
public DataTable SessionDataSource
{
    get
    {
        string sessionKey = "SessionDataSource";

        if (Session[sessionKey] == null || !IsPostBack)
        {
            Session[sessionKey] = OrdersTable();
        }
        return (DataTable)Session[sessionKey];
    }
}
#endregion

#region RadGrid Events for CRUD Operations

// CREATE (Add New Record)
protected void RadGrid1_InsertCommand(object sender, GridCommandEventArgs e)
{
    GridEditableItem editedItem = e.Item as GridEditableItem;

    DataRow newRow = SessionDataSource.NewRow();

    //As this example demonstrates only in-memory editing, a new primary key value should be generated
    //This should not be applied when updating directly the database
    DataRow[] allValues = SessionDataSource.Select("OrderID = MAX(OrderID)");

    if (allValues.Length > 0)
    {
        newRow["OrderID"] = int.Parse(allValues[0]["OrderID"].ToString()) + 1;
    }
    else
    {
        newRow["OrderID"] = 1; //the table is empty;
    }

    //Set new values
    Hashtable newValues = new Hashtable();
    //The GridTableView will fill the values from all editable columns in the hash
    e.Item.OwnerTableView.ExtractValuesFromItem(newValues, editedItem);

    try
    {
        foreach (DictionaryEntry entry in newValues)
        {
            newRow[(string)entry.Key] = entry.Value;
        }
    }
    catch (Exception ex)
    {
        Label1.Text += string.Format("<br />Unable to insert into Orders. Reason: {0}", ex.Message);
        e.Canceled = true;
        return;
    }

    SessionDataSource.Rows.Add(newRow);
    //Code for updating the database ca go here...
    Label1.Text += string.Format("<br />Order {0} inserted", newRow["OrderID"]);
}

// READ (data binding)
protected void RadGrid1_NeedDataSource(object sender, GridNeedDataSourceEventArgs e)
{
    RadGrid1.DataSource = SessionDataSource;
}

// UPDATE
protected void RadGrid1_UpdateCommand(object sender, GridCommandEventArgs e)
{
    GridEditableItem editedItem = e.Item as GridEditableItem;

    //Locate the changed row in the DataSource
    DataRow[] changedRows = SessionDataSource.Select(string.Format("OrderID = {0}", editedItem.GetDataKeyValue("OrderID")));

    if (changedRows.Length != 1)
    {
        this.Label1.Text += "Unable to locate the Order for updating.";
        e.Canceled = true;
        return;
    }
    //Update new values
    Hashtable newValues = new Hashtable();
    e.Item.OwnerTableView.ExtractValuesFromItem(newValues, editedItem);
    changedRows[0].BeginEdit();
    try
    {
        foreach (DictionaryEntry entry in newValues)
        {
            changedRows[0][(string)entry.Key] = entry.Value;
        }
        changedRows[0].EndEdit();
    }
    catch (Exception ex)
    {
        changedRows[0].CancelEdit();
        Label1.Text += string.Format("Unable to update Orders. Reason: {0}", ex.Message);
        e.Canceled = true;
        return;
    }
}

// DELETE
protected void RadGrid1_DeleteCommand(object sender, GridCommandEventArgs e)
{
    GridDataItem dataItem = e.Item as GridDataItem;
    string ID = dataItem.GetDataKeyValue("OrderID").ToString();

    if (SessionDataSource.Rows.Find(ID) != null)
    {
        SessionDataSource.Rows.Find(ID).Delete();
    }
}
#endregion

#region DataSource
private DataTable OrdersTable()
{
    DataTable dt = new DataTable();

    dt.Columns.Add(new DataColumn("OrderID", typeof(int)));
    dt.Columns.Add(new DataColumn("OrderDate", typeof(DateTime)));
    dt.Columns.Add(new DataColumn("Freight", typeof(decimal)));
    dt.Columns.Add(new DataColumn("ShipName", typeof(string)));
    dt.Columns.Add(new DataColumn("ShipCountry", typeof(string)));

    dt.PrimaryKey = new DataColumn[] { dt.Columns["OrderID"] };

    for (int i = 0; i < 70; i++)
    {
        int index = i + 1;

        DataRow row = dt.NewRow();

        row["OrderID"] = index;
        row["OrderDate"] = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 0, 0, 0).AddHours(index);
        row["Freight"] = index * 0.1 + index * 0.01;
        row["ShipName"] = "Name " + index;
        row["ShipCountry"] = "Country " + index;

        dt.Rows.Add(row);
    }

    return dt;
}
#endregion

protected void rddl_Vendors_DataBinding(object sender, EventArgs e)
{
    var rddl = (RadDropDownList)sender;
    rddl.DataSource = OrdersTable();
}