Inheriting Grid Columns

In some scenarios you may want to extend the default functionality of GridColumn (including additional properties for it, embedding extra controls in its cells, etc.). The proper way to accomplish this task is by inheriting the corresponding default GridColumn class (in your own class) and overriding the InitializeCell(cell, columnIndex,gridItem) method of that class. Thus you can reuse the custom configuration of your choice in all your grid instances in your application.The example below shows a basic approach how to redefine the object model for GridBoundColumn:

ASP.NET

<%@ Register tagprefix="custom" namespace="MyNamespace" %>
<telerik:RadGrid RenderMode="Lightweight" ID="RadGrid1" DataSourceID="SqlDataSource1" AllowPaging="True"
  AllowSorting="True" runat="server" AutoGenerateColumns="false">
  <MasterTableView DataKeyNames="CustomerID">
    <Columns>
      <custom:MyCustomColumn DataField="CustomerID" HeaderText="CustomerID">
      </custom:MyCustomColumn>
    </Columns>
  </MasterTableView>
</telerik:RadGrid>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
   SelectCommand="SELECT * FROM [Customers]"></asp:SqlDataSource>

C#

public class MyCustomColumn : GridBoundColumn
{

    public override void InitializeCell(System.Web.UI.WebControls.TableCell cell, int columnIndex, Telerik.Web.UI.GridItem inItem)
    {
        if (inItem is GridHeaderItem)
        {
            cell.Text = this.DataField;
        }
        if (inItem is GridDataItem)
        {
            string ID = inItem.OwnerTableView.DataKeyValues[inItem.ItemIndex]["CustomerID"];
            cell.Controls.Add(new LiteralControl(ID));
        }
    }
}

VB

Namespace MyNamespace

  Public Class MyCustomColumn
      Inherits GridBoundColumn

       Public Overrides Sub InitializeCell(ByVal cell As System.Web.UI.WebControls.TableCell, ByVal columnIndex As Integer, ByVal inItem As
      Telerik.Web.UI.GridItem)
           If TypeOf inItem Is GridHeaderItem Then
              cell.Text = Me.DataField
           End If
           If TypeOf inItem Is GridDataItem Then
               Dim ID As String = inItem.OwnerTableView.DataKeyValues(inItem.ItemIndex)( "CustomerID")
              cell.Controls.Add( New LiteralControl(ID))
           End If
       End Sub
  End Class
End Namespace

When inheriting grid columns in hierarchy, you need to override their Clone() method and copy the base properties as follows:

C#

public override GridColumn Clone()
{
    RequiredGridBoundColumn requiredGridBoundColumn = new RequiredGridBoundColumn();

    //you should override CopyBaseProperties if you have some column specific properties
    requiredGridBoundColumn.CopyBaseProperties(this);

    return requiredGridBoundColumn;
}

VB

Public Overloads Overrides Function Clone() As GridColumn
    Dim requiredGridBoundColumn As New RequiredGridBoundColumn()

    'you should override CopyBaseProperties if you have some column specific properties
    requiredGridBoundColumn.CopyBaseProperties(Me)

    Return requiredGridBoundColumn
End Function

Note that we do not support issues with inherited versions of RadGrid and the purpose of this topic is to provide basic instructions how to inherit your custom grid columns from RadGrid.