Thank you both for your inputs. As for why I couldn't delete any rows, I figured out what the problem was.
My code that gave value to my parameter for the DELETE statement, returned:
"System.Data.DataRowView"
E.g. it returned the object, and not the value as string.
So I changed my code to this:
DataRowView oDataRowView = comboBox1.SelectedItem as DataRowView;
string sValue = string.Empty;
if (oDataRowView != null) {
sValue = oDataRowView.Row["column1"] as string;
sqlCmd.Parameters.Add("@myParameter", SqlDbType.NVarChar).Value = sValue = oDataRowView.Row["column1"] as string;
sqlCmd.CommandType = CommandType.Text;
sqlCmd.ExecuteNonQuery();
I still have to tackle the issue OriginalGriff gave me an answer to, but at least this (the main issue) got resolved.
I have a sneaking suspicion that what I pasted above is not as efficient as it could be, although it works.
If anyone sees any bloats, feel free to tell me.