DataGridView Validation & Changing Cell Value

Question

I would like to manipulate a cell in my DataGridView when it is validating so that if the user enters a value that is not valid for the database, but is easily converted to valid data, the program will change the value to an appropriate one.

I am able to validate my value properly but when I try to change it to something valid I get a DataError. Here is my code:

        private void unit_List_2_GroupsDataGridView_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
    {
        Console.WriteLine("Validating");
        DataGridViewColumn col = this.unit_List_2_GroupsDataGridView.Columns[e.ColumnIndex];
        DataGridViewCell cell = this.unit_List_2_GroupsDataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex];
        if (col == this.batchDataGridViewTextBoxColumn && this.unit_List_2_GroupsDataGridView.IsCurrentCellInEditMode)
        {
            Console.WriteLine("   Batch Column");
            DataRow[] rows = label_EntryDataSet.viewJobBatchList.Select(String.Format("Job={0} AND Display='{1}'"
                , comboBox1.SelectedValue, e.FormattedValue));
            if (rows.Length == 1)
            {
                Console.WriteLine("      Auto Completed item from list: {0}", rows[0]["Batch"]);
                //e.Cancel = true;
                cell.Value = rows[0]["Batch"];
                //this.unit_List_2_GroupsDataGridView.EndEdit();
            }
            else
            {
                Console.WriteLine("     No Autocomplete!");
                int i = 0;
                if (!int.TryParse(e.FormattedValue.ToString(), out i))
                {
                    Console.WriteLine("         Not an integer either");
                    e.Cancel = true;
                }
            }
        }
    }

The line that reads cell.Value = rows[0]["Batch"]; is not doing what I expect it to do.

Please post the exact error message and point out which line of code is mentioned. — David, Jan 20 '11 at 02:50

score 49 · Accepted Answer · answered Jan 20 '11 at 03:04

49

The CellValidating event occurs just prior to when the DataGridView leaves edit mode; it's an event that relates-to/involves the editing control (DataGridView.EditingControl). You should never attempt to change the cell value in the handler for this event, because unless you cancel the event (in which case the user is stuck in edit mode), the cell value is set to the value from the editing control immediately after the event finishes. This, therefore, undoes any action you perform in the handler.

What you have to do instead is change the value in the editing control (remembering not to cancel the event). For example, for a DataGridViewTextBoxCell, you would use the following instead of your problematic line:

unit_List_2_GroupsDataGridView.EditingControl.Text = Convert.ToString(rows[0]["Batch"]);

You should find that this solves your issue.

answered Jan 20 '11 at 03:04

Bradley Smith

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Your response was great and saved me lots of time. Is there a way to change the dgv cell Style Format and cell Tag from within the CellValidating event? I've tried a few things and have searched for answers without luck so far. – Cincy Steve Jul 17 '12 at 18:44
@SteveRehling You should be able to set the `Tag` property at any point in time. I haven't tried changing the cell style inside the `CellValidating` event; my advice would be to place this code in the `CellValueChanged` event instead (if possible). – Bradley Smith Jul 18 '12 at 00:22
If your column is not of String type, be sure to toString() the value before comparison. When changing the edited value be sure to make this type a string. – MrOli3000 Dec 12 '14 at 10:01
Thanks Bradley Smith, so great , since years together i was searching the best way to the situation. – sushil.agarwal Jun 16 '20 at 17:51

score 5 · Answer 2 · answered Nov 21 '13 at 14:22

5

In general, it is better to use the CellParsing event whenever you need to convert/change the value in a cell. From within that event, you can indicate that the user's value is invalid by setting the ErrorText value of the cell or row.

answered Nov 21 '13 at 14:22

drwatsoncode

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This answer solved my particular problem, but it was still necessary to handle CellValidating as well, because if the user's entry is garbage and I cannot correct it while handling CellParsing, I still want to keep them in edit mode (which can't be done when handling CellParsing). It is worth noting that in such circumstances, CellValidating is raised before CellParsing. – Morris Sep 26 '19 at 10:26

DataGridView Validation & Changing Cell Value

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