编辑没有绑定源的DataGridView单元格？

New to .NET/C# stuff so please forgive me if it's something obvious ;-) I'm trying to get cell editing going on a DataGridView control (WinForms). I've set all "ReadOnly"-type options to false, I've set EditMode to "EditOnEnter", I've added a row and selected a current cell programmatically, I've tried calling BeginEdit() but all to no avail - I can't edit the cell's contents.New to .NET/C# stuff so please forgive me if it