external multi-column-combo-box problem

Oct 25 at 5:11 PM
hello,
I wanted to use the multi-column-combo-box from
https://www.intertech.com/Blog/winforms-multi-column-combo-box-in-a-datagridview/,

but there is a problem in the Multi Column Combo after compiling
 // Set custom properties of Multi Column Combo Box.
editingControl.ColumnNames = ColumnNames;
editingControl.ColumnWidths = ColumnWidths;
editingControl.BackColorEven = EvenRowsBackColor;
editingControl.BackColorOdd = OddRowsBackColor;
editingControl.OwnerCell = this;

if (Value != null) //<--- error here
Is there any chance of finding the solution and make both extensions to cooperate?