C#

using System.Windows.Forms;
using System.Data;
static class Program {
	static void Main() {
		Application.Run(new Frm());
		}
	}

class Frm: Form {
	public Frm() {
		DataTable table = new DataTable();
		DataColumn[] keys = new DataColumn[1];
		DataColumn column1 = new DataColumn();
		DataColumn column2 = new DataColumn();
		DataGrid grid = new DataGrid();
		
		grid.Dock = DockStyle.Fill;
		table.Columns.Add(column1);
		table.Columns.Add(column2);
		keys[0] = column2;
		table.PrimaryKey = keys;
		Controls.Add(grid);
		table.RowChanging += new DataRowChangeEventHandler(OnRowChanging);
		grid.SetDataBinding(table, "");
		}

	private void OnRowChanging(object sender, DataRowChangeEventArgs e) {
		if (e.Action == DataRowAction.Add) {
			string pk = e.Row.Table.PrimaryKey[0].ColumnName;
			if (e.Row[pk] == null)
				e.Row[pk] = new System.Guid();
			}
		}
	}