<Schema>
    <Model ID="CustomerID">
        <%--<telerik:ClientDataSourceModelField FieldName="CustomerID" DataType="Number" />
        <telerik:ClientDataSourceModelField FieldName="CompanyName" DataType="String" />
        <telerik:ClientDataSourceModelField FieldName="ContactName" DataType="String" />
        <telerik:ClientDataSourceModelField FieldName="ContactTitle" DataType="String" />--%>
    </Model>
</Schema>

protected void RadClientDataSource1_Init(object sender, EventArgs e)
{
    var clientDataSource = sender as RadClientDataSource;
    foreach (GridColumn col in RadGrid1.Columns)
    {
        if (col is GridBoundColumn)
        {
            clientDataSource.Schema.Model.Fields.Add(new ClientDataSourceModelField() { FieldName = (col as GridBoundColumn).DataField });
        }
    }

}

protected void RadGrid1_Init(object sender, EventArgs e)
{
    var grid = sender as RadGrid;
    foreach (ClientDataSourceModelField item in RadClientDataSource1.Schema.Model.Fields)
    {
        grid.Columns.Add(new GridBoundColumn()
        { 
            HeaderText = item.FieldName,
            DataField = item.FieldName
        });
    }
}