Cannot edit DataGridView-cell, Validating-event sets e.Cancel = true

Question

The DatagridView drives me crazy again. So i have a form with a DatagridView which works until now. But now there's an invalid value in the database which causes the Validating event to block the program flow.

This is it:

private void GrdChargeAssignment_Validating(Object sender, DataGridViewCellValidatingEventArgs e)
{
    e.Cancel = false;
    var grid = (DataGridView)sender;
    ErpService.ArrivalChargeAssignment ass = grid.Rows[e.RowIndex].DataBoundItem as ErpService.ArrivalChargeAssignment;

    string countValue = grid.Rows[e.RowIndex].Cells[AssignedCol.Name].EditedFormattedValue.ToString();
    if (string.IsNullOrWhiteSpace(countValue))
    {
        grid.Rows[e.RowIndex].Cells[AssignedCol.Name].Value = "0";
        countValue = "0";
    }

    int count;
    if (!int.TryParse(countValue, out count))
    {
        grid.Rows[e.RowIndex].ErrorText = "Insert a valid integer for count!";
        e.Cancel = true;
    }
    else if (count > ass.Count_Actual)
    {
        grid.Rows[e.RowIndex].ErrorText = string.Format("Please insert a count between 0 and arrival-count({0})!", ass.Count_Actual);
        e.Cancel = true;  // !!!! HERE !!!!
    }

    if (e.Cancel == false)
        grid.Rows[e.RowIndex].ErrorText = "";
}

The line that i've commented with !!!! HERE !!!! !!!! HERE !!!! causes the event to be canceled which blocks the gui. The user cannot edit this invalid value.

During databinding i have already unsubscribed from this event to disable it. But now it is still triggered if the user clicks into the cell to edit the invalid value. The call-stack window shows that it's triggered internally from the CellMouseDown -event. How can i prevent this? I want it to be validated only if the user has edited a cell and leaves it.

Answer 1

If you only want to validate when the user changes the value, could you check for modifications before applying the validation? Something like:

else if (count > ass.Count_Actual)
{
    if( count == ass.Count )
    {
        // The data has not changed, do not validate
    }
    else
    {
        grid.Rows[e.RowIndex].ErrorText = string.Format("Please insert a count between 0 and arrival-count({0})!", ass.Count_Actual);
        e.Cancel = true;  // !!!! HERE !!!!
    }
}

If the user edits the value to another invalid value, the validation will kick in, otherwise, the bad data is ignored.