Samples:
private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e) { // Validate the CompanyName entry by disallowing empty strings. if (dataGridView1.Columns[e.ColumnIndex].Name == "CompanyName") { if (e.FormattedValue.ToString() == String.Empty) { dataGridView1.Rows[e.RowIndex].ErrorText = "Company Name must not be empty"; e.Cancel = true; } } }