Using Combo box in Datagridview

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C#

C#4.0

Telerik

I'm Using Telerik RadDataGridview Component and
Bind a Table to my grid by LINQ instructions
How to show a defined column as combo box when i
edit the row?

I can use following code for example

GridViewComboBoxColumn comboCol = new GridViewComboBoxColumn("col5");
			comboCol.DataSource = colors;
			comboCol.DisplayMember = "Name";
			comboCol.ValueMember = "Name";
			radGridView1.Columns.Add(comboCol); 

but i want use loaded columns as combo box and dont want
add a new column.

what shall i do?