How to show ErrorIcon in DataGridViewCll on Cell TextChange?

Question

I have two columns in a DataGridView:

• orderdQuantity
• receivedQuantity

If I input receivedQuantity greater than orderdQuantity, then on that cell TextChanged event, I want to display ErrorIcon.
Currently, it is not functioning as I previously described. What currently is working is, if I click on another cell of DataGridview, then ErrorIcon is displayed.

My code is the following:

//txtBox_TextChanged is called in datagridview1_EditingControlShowing() event

private void txtBox_TextChanged(object sender, EventArgs e)
{
    try
    {
        if (datagridview1.Rows.Count > 0)
        {
            if (txtBox.Text != "")
            {
                int rowIndex = datagridview1.CurrentRow.Index;
                int recQty = Convert.ToInt32(txtBox.Text);
                int orderedQty = Convert.ToInt32(datagridview1.Rows[rowIndex].Cells["Ordered Qty"].Value);
                if (recQty > orderedQty)
                {
                    this.datagridview1.CurrentCell.ErrorText = "Invalid Quantity";
                }
            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show("Oops something went wrong.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

Answer 1

How can I show the error icon when the user is typing in the cell?

By default when you set ErrorText for a cell, the error icon will not show when the cell is in edit mode. Also none of events of the DataGridView handles change of text while the user is typing in a cell. To set an error text and show error icon while the user is typing in a cell you should follow these steps:

• Get the editing control in EditingControlShowing and handle its TextChanged event.
• In the TextChanged event of the text box, set or remove ErrorText for the cell.
• Apply a right padding to the cell when starting edit and in CellBeginEdit event and remove it in CellEndEdit.
• Paint error icon in CellPainting event.

Example

This example shows an error in cell while the user types in the first cell if the text of the cell become empty.

In EditingControlShowing attach TextChanged event to the TextBox:

void grid_EditingControlShowing(object sender,DataGridViewEditingControlShowingEventArgs e)
{
    if (this.grid.CurrentCell.ColumnIndex == 0)
    {
        var textbox = e.Control as DataGridViewTextBoxEditingControl;
        if (textbox != null)
        {
            textbox.TextChanged -= textBox_TextChanged;
            textbox.TextChanged += textBox_TextChanged;
        }
    }
}

In TextChanged event of TextBox perform validation and remove or set ErrorText for the cell:

void textBox_TextChanged(object sender, EventArgs e)
{
    var textbox = (TextBox)sender;
    if (string.IsNullOrEmpty(textbox.Text))
        this.grid.CurrentCell.ErrorText = "Invalid Value";
    else
        this.grid.CurrentCell.ErrorText = null;
}

In CellBeginEdit add a right padding to show error Icon and in CellEndEdit we remove the padding:

void grid_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
{
    var cell = grid.Rows[e.RowIndex].Cells[e.ColumnIndex];
    cell.Style.Padding = new Padding(0, 0, 18, 0);
}
void grid_CellEndEdit(object sender, DataGridViewCellEventArgs e)
{
    var cell = grid.Rows[e.RowIndex].Cells[e.RowIndex];
    cell.Style.Padding = new Padding(0, 0, 0, 0);
}

In CellPainting draw error icon yourself:

private void grid_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    e.Paint(e.ClipBounds, DataGridViewPaintParts.All &
                        ~(DataGridViewPaintParts.ErrorIcon));
    if (!String.IsNullOrEmpty(e.ErrorText))
    {
        GraphicsContainer container = e.Graphics.BeginContainer();
        e.Graphics.TranslateTransform(e.CellStyle.Padding.Right, 0);
        e.Paint(e.CellBounds, DataGridViewPaintParts.ErrorIcon);
        e.Graphics.EndContainer(container);
    }
    e.Handled = true;
}