convert textboxcolumn into combobox column in c#.net window application

1st option:
at first you have to copy the entries of the column
2nd, delete the column
3rd, add the new column as required type
4th, fill the column with the entries

2nd option:
always create and edit 2 colums (one combo, one text) and just switch visibility between both if you need to


ps:
you will get textlines to items with something like this
[code]
foreach(var x in text.replace('\r', string.empty).split('\n'))
combobox.itmes.add(x);
[/code]

and other way around:
[code]
text = string.concat(combobox.items, "\r\n");
[/code]