//to create combobox in the datagrid
            DataGridViewComboBoxColumn t = new DataGridViewComboBoxColumn();

            // to display data in combobox from database

            SqlDataAdapter da1 = new SqlDataAdapter("select Name from stdu",cn);

            DataSet  ds1 = new DataSet();

            da1.Fill(ds1,"stdu");

            t.DataSource = ds1.Tables["stdu"];

            t.DisplayMember = "Name";

            t.DataPropertyName = "Name";