How to convert DataGridViewComboBoxCell to DataGridViewTextBoxCell

Question

I searched a lot for this error many same question is already asked, but its not solving my problem. I am getting

Operation is not valid because it results in a reentrant call to the SetCurrentCellAddressCore function.

The scenario is I have datagridview with TextboxColumn I am using CellBeginEdit to convert it in ComboBoxColumn, and after CellValidate I again change ComboBoxColumn to TextboxColumn. The codes works for all. but getting said error in exact line e.RowIndex = 2 throws this exception, but others rows doses not show error. if I omit this error and continue then e.RowIndex = 2 cell value comes blank, and other rows value work.

Here is the code of CellBeginEdit

 if (e.ColumnIndex == 2 && e.RowIndex >= 0)
  {
    try
     {
      string s = Convert.ToString(_dgvCoarseAggegateTest[e.ColumnIndex, e.RowIndex].Value);
      string s1 = Convert.ToString(_dgvCoarseAggegateTest[e.ColumnIndex, 0].Value);
      DataGridViewComboBoxCell c = new DataGridViewComboBoxCell();

      string _SizeName = _cGetParrent._mGetParentCellValue(ref _dgvCoarseAggegateTest, e.RowIndex, 1);                  
      _mFillSieveSizeGridCombo(_mGetMetalSizeID(_SizeName), ref c); // Here My Combo Will GetValues from SQL and it Returning Value
      _dgvCoarseAggegateTest[e.ColumnIndex, e.RowIndex] = c; // Heres the error When e.RowIndex == 2 and if e.RowIndex != 2 then no error
      _dgvCoarseAggegateTest[e.ColumnIndex, e.RowIndex].Value = s;
      _dgvCoarseAggegateTest[e.ColumnIndex, 0].Value = s1;
     }
     catch (Exception ex)
      {
        MessageBox.Show(ex.Message);
      }
    }

How to resolve this.

UPDATE : No rows there user will add new row and select values, the base thing is i want to show combo and fill values from database, the fill values is depends on condition, so every time new values will come,

Sample Data

testTable
1      A
2      B
3      C
4      D
5      E
6      F
7      G
8      H
9      I

In column1 I added one combo with values from 1 to 9, in _mFillSieveSizeGridCombo I am passing id to sql server 2008 and filling combo using Combo.Item.Add(x) method.

Answer 1

There is a flag inside SetCurrentCellAddressCore() preventing any re-entrant call corrupting internal values of DataGridView. Usaully an event was raised with the flag = true and reset at the end of event.

To workaround this, you can simply add a wrapper of BeginInvoke() inside the event, to get your process run after the event with async.

EDIT

The issue can be reproduce in EditOnEnter mode, and the setter of cell outside the event in BeginInvoke results the indefinite loop

private bool _suppressCellBeginEdit = false;
private void dgv_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
{
    var dgv = sender as DataGridView;
    if (_suppressCellBeginEdit)
        return;

    if (e.ColumnIndex == 2 && e.RowIndex >= 0)
    {
        string s = Convert.ToString(dgv[e.ColumnIndex, e.RowIndex].Value);
        string s1 = Convert.ToString(dgv[e.ColumnIndex, 0].Value);
        DataGridViewComboBoxCell c = new DataGridViewComboBoxCell();

        c.Items.Add(string.Format("x{0}:y{1} {2}", e.RowIndex, e.ColumnIndex, 0));
        c.Items.Add(string.Format("x{0}:y{1} {2}", e.RowIndex, e.ColumnIndex, 1));
        c.Items.Add(string.Format("x{0}:y{1} {2}", e.RowIndex, e.ColumnIndex, 2));

        // special handling
        if (e.RowIndex == e.ColumnIndex)
        {
            this.BeginInvoke(new Action(() =>
            {
                _suppressCellBeginEdit = true;
                this.Invoke(new Action(() => 
                    {
                        c.Value = s;
                        dgv[e.ColumnIndex, e.RowIndex] = c;
                        dgv[e.ColumnIndex, 0].Value = s1;
                    }));
                _suppressCellBeginEdit = false;
            }));
        }
        else
        {
            c.Value = s;
            dgv[e.ColumnIndex, e.RowIndex] = c;
            dgv[e.ColumnIndex, 0].Value = s1;
        }
    }
}

Answer 2

As you can tell from the trouble you are having implementing this, DataGridView is very unhappy about you trying to pull the floor mat. It explicitly forbids changing the cell object at critical moments. While it is handling an event itself is such a critical moment. A generic problem with events, called re-entrancy. The trouble you are having with @Eric's approach shows that it is indeed a tricky issue to solve.

So what you do not want to do is modify the cell type or reference. Keep your eyes on the ball, what you really want to do is modify the content of the dropdown list. That is not a problem. Get back to the designer and change the ColumnType property of the column to DataGridViewComboBoxColumn. And use the CellBeginEdit event to dynamically alter the combobox items collection. A simple example:

    private void _dgvCoarseAggegateTest_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e) {
        var dgv = (DataGridView)sender;
        if (e.ColumnIndex == 2) {
            var cell = (DataGridViewComboBoxCell)dgv.Rows[e.RowIndex].Cells[e.ColumnIndex];
            cell.Items.Clear();
            // Run your dbase query here to fill cell.Items
            //...
            // We'll just fake it here for demo purposes:
            cell.Items.Add(e.RowIndex.ToString());
            cell.Items.Add((e.RowIndex+1).ToString());
            cell.Items.Add((e.RowIndex+2).ToString());
        }
    }

Answer 3

Here is a workaround: In the CellBeginEdit event first check to see if the ColumnType is DataGridViewComboBoxCell. If it isn't we cancel the event, call a function that changes the column type and then call the event once more:

void switchCellType(object sender, DataGridViewCellCancelEventArgs e)
{
    DataGridViewComboBoxCell c = new DataGridViewComboBoxCell();
    // prepare the cell:
    //..
    // fill the drop down items..
    c.Items.Add("1");  // use
    c.Items.Add("2");  // your 
    c.Items.Add("3");  // code here!
    DGV[e.ColumnIndex, e.RowIndex] = c;  // change the cell
    DGV_CellBeginEdit(sender, e);        // restart the edit with the original parms  
}


private void DGV_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
{

    DataGridViewCell cell = DGV[e.ColumnIndex, e.RowIndex];
    if (!(cell is DataGridViewComboBoxCell))
    {
        e.Cancel = true;
        switchCellType(sender, e);
        return;
    }
    //..

Now your code can proceed, obviously without the cell changing. Possibly you want to pass in the text value to set as well..

Note that you will have to make sure that the CellEndEdit event doesn't revert the change before its time!! Maybe a flag, maybe in the Tag will help. If you want I can have a look at your CellEndEdit code, if there is any..