No need for
Datacolumns
at top. Do like below
dtStaff.Columns.Clear();
dtStaff.Columns.Add("StaffID", typeof(Int32));
dtStaff.Columns.Add("FullName", typeof(String));
Or Create a
Datacolumn
at top & use it below for adding columns.
DataColumn dtColumn;
dtColumn = new DataColumn();
dtColumn.DataType = typeof(Int32);
dtColumn.ColumnName = "StaffID";
dtColumn.Caption = "Staff ID";
dtStaff.Columns.Add(dtColumn);
And learn about
SQL Injection[
^]. Change your code ASAP.