Question

Lets simplify. Lets say I have this class:

class Foo
{
    public string Name { get; set; }
    public int Age { get; set; }
    public int height{ get; set; }
    ...
}

and I have a DataGridView.DataSource bound to a BindingList<Foo> with N columns, each one bound to each property.

I need to:

• Allow the user to enter non validating ages, heights, etc (for instance “aaa”)
• Color the cells with non validating values (red background)
• Retain the non validating values displayed until the form is closed (I don’t want to lose the values entered until the form is closed, so the user has the option to correct the bad cells anytime he wants BEFORE closing the form)
• Keep the last correct values entered for each cell with non validating values entered.
• When the form is closed, ditch the non validating values and keep the last correct values entered.

Is there any easy way to do this?

Answer 1

I’ve got same problem with date column yesterday.

I’ve found CellFormatting and CellParsing events, but BindingSource seems to ignore them. So I did it like this. I’ve used cell. Tag property. dgv is DataGridView here.

  private void dgv_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
    {
        if (IsBirthdayColumn(e.ColumnIndex))
        {
            e.Value = dgv[e.ColumnIndex, e.RowIndex].Tag;
            if (e.Value is DateTime)
            {
                e.Value = ((DateTime)e.Value).ToShortDateString();
            }
            e.FormattingApplied = true;
        }
    }

    private void dgv_CellParsing(object sender, DataGridViewCellParsingEventArgs e)
    {
        DateTime date;
        if (IsBirthdayColumn(e.ColumnIndex))
        {
            if (e.Value != null && DateTime.TryParse(e.Value.ToString(), out date))
            {
                e.Value = date;
                dgv[e.ColumnIndex, e.RowIndex].Tag = e.Value;
            }
            else
            {
                dgv[e.ColumnIndex, e.RowIndex].Tag = e.Value;
                e.Value = DBNull.Value;
            }
            e.ParsingApplied = true;
        }
    }

   private void dgv_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
    {
        DateTime date;
        if (IsBirthdayColumn(e.ColumnIndex))
        {
            var cell = dgv[e.ColumnIndex, e.RowIndex];
            if (e.FormattedValue != null && !DateTime.TryParse(e.FormattedValue.ToString(), out date))
            {
                if (e.FormattedValue.ToString().Trim().Equals(""))
                {
                    cell.ErrorText = string.Empty;
                    return;
                }
                cell.ErrorText = "Invalid date format";
            }
            else
            {
                cell.ErrorText = string.Empty;
            }
        }
    }

Also u need to handle DataError event

    private void dgv_DataError(object sender, DataGridViewDataErrorEventArgs e)
    {
        ......
        e.Cancel = false;
        ......
    }

Now u can write anything in date column. In the case of invalid date it will show u error icon and save DBNull in DataSet. In the case of empty string it will just save DBNull.