validate Datagridview column

If you want to validate the column in the datagridview then you can choose "CellValidating"

Sample Codeing is as below

 private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
       {
           DataGridViewTextBoxCell cell = dataGridView1[e.ColumnIndex, e.RowIndex] as DataGridViewTextBoxCell;

           if (cell != null)
           {
               char[] chars = e.FormattedValue.ToString().ToCharArray();
               foreach (char c in chars)
               {
                   if (char.IsDigit(c) == false)
                   {
                       MessageBox.Show("You have to enter digits only");
                     
                       e.Cancel = true;
                       break;
                   }
               }
           }
       }

Suppose if you want to validate after pressing enter, then you can use as below

protected override bool ProcessDialogKey(Keys keyData)
    {
        if (keyData == Keys.Enter)
        {
            DataGridViewCell currentCell = CurrentCell;
            EndEdit();
            CurrentCell = null;
            CurrentCell = currentCell;
            return true;
        }
        return base.ProcessDialogKey(keyData);
    }

else you can also use EditControlShowing event

void dataGridView1_EditingControlShowing(object sender,
                 DataGridViewEditingControlShowingEventArgs e)
            {
                if (this.dataGridView1.CurrentCell.ColumnIndex == 0)
                {
                    if (e.Control is TextBox)
                    {
                        TextBox tb = e.Control as TextBox;
                        tb.KeyPress -= new KeyPressEventHandler(tb_KeyPress);
                        tb.KeyPress += new KeyPressEventHandler(tb_KeyPress);
                    }
                }
            }
 
            void tb_KeyPress(object sender, KeyPressEventArgs e)
            {
                if (!(char.IsDigit(e.KeyChar)))
                {
                    Keys key = (Keys)e.KeyChar;
 
                    if (!(key == Keys.Back || key == Keys.Delete))
                    {
                        e.Handled = true;
                    }
                }
            }
        }