private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e) { for(int i=0;i<dataGridView1.rows.count;i++) { if(e.RowIndex!=i) { if(dataGridView1.Rows[i].Cells[0].Value.ToString()==dataGridView1.Rows[e.RowsIndex].Cells[0].Value.ToString()) { MessageBox.Show("Cette valeur set dejé dans une autre ligne"); dataGridView1.Rows[e.RowsIndex].Cells[0].Value = ""; dataGridView1.Rows[e.RowIndex].Selected=true; } } } }