Question

Background

When I hit a button on a WinForm, I am loading data into a BindingSource that serves as the data source for a DataGridView. Once the data is loaded, I go through and make some modifications to the DataGridView; in particular, I 1) set any cells that are valued as DBNull to the string value “NULL”, 2) italicize the same cells, and 3) highlight some rows.

Simple example of what I’m doing:

private void btnFetch_Click(object sender, EventArgs e)
{
    // If there's already a DataSource, Dispose of it.
    if (bsMessageTracking.DataSource != null)
    {
        (bsMessageTracking.DataSource as DataTable).Dispose();
    }

    // Get new DataSource.
    bsMessageTracking.DataSource = GetDataTable(); // Details not relevant.

    // Show NULL values.
    foreach (DataGridViewRow row in dgv.Rows)
    {
        foreach (DataGridViewCell cell in row.Cells)
        {
            if (cell.Value is DBNull)
            {
                cell.Value = "NULL";
                cell.Style.Font = new Font(dgv.DefaultCellStyle.Font, FontStyle.Italic);
            }
        }
    }

    // Apply highlighting.
    foreach (DataGridViewRow row in dgvMessageTracking.Rows)
    {
        if (HighlightRow(row)) // Details not relevant.
        {
            row.DefaultCellStyle.BackColor = Color.LightYellow;
        }
    }
}

The data gets loaded based on input into a TextBox on the form.

Situation

Everything works great if this occurs on the button click. However, in order to provide some convenience to the user, I am allowing this form to get loaded with data prepopulated – the main form will instantiate this form with the data to put into the TextBox, and this btnFetch_Click handler will get called from the constructor:

internal MessageTracking(string ID)
{
    InitializeComponent();

    // Setup data source.
    dgvMessageTracking.DataSource = bsMessageTracking;

    // Set ID and run query.
    if (ID != null)
    {
        // Set ID.
        txtlID.Text = ID;

        // Run!
        btnFetch_Click(null, null);
    }
}

The value of the cells gets changed (so I see NULL), but the font and the highlighting don’t stick.

What I’ve tried

If I replicate the highlighting code in the OnShown method, the highlighting sticks. However, replicating the font code there doesn’t work. I can make the font stick if I put it in CellFormatting, but that seems like overkill to me, because I only need this to be run once when the form is loaded – it works fine if the process is run after the form is visible.

Plea

If anyone has any suggestions, I would appreciate them. Thanks!

Answer 1

I guess, from the lack of responses, that there is no better way if you want the formatting shown when the form first becomes visible. I have removed the Show NULL values portion of the btnFetch_Click handler and added this dgvMessageTracking_CellFormatting handler to handle this functionality at all times:

private void dgvMessageTracking_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    if (e.Value is DBNull)
    {
        e.Value = "NULL";
        e.CellStyle.Font = new Font(dgvMessageTracking.DefaultCellStyle.Font, FontStyle.Italic);
    }
}