Question

I’m creating a settings form that is quite similar to the Visual Studio 2008 “Connect To Database” form in the Server Explorer.

The settings form is opened as a modal dialog from the parent form as follows:

    private void settingsToolStripMenuItem_Click(object sender, EventArgs e)
    {
        var SettingsForm = new frmSettings();
        SettingsForm.ShowDialog(this); 
    }

On the SettingsForm, I have a ComboBox that will populate its list with the SQLServer instance names available on the network through the following code in the DropDown event:

    private void cboTrackingServerName_DropDown(object sender, EventArgs e)
    {
        DataTable dt = SmoApplication.EnumAvailableSqlServers(false);
        if (dt.Rows.Count > 0)
        {
            cboTrackingServerName.Items.Clear();

            foreach (DataRow row in dt.Rows)
            {
                cboTrackingServerName.Items.Add(
                     row["Server"] + "\\" + row["Instance"]);
            }
        }
    }

The problem is that whenever the user clicks the DropDown arrow on the ComboBox, the SettingsForm loses focus to its parent form for a quick second, the SettingsForm appears to redraw itself, and then the SettingsForm regains focus. This also causes the actual DropDown list not to appear until the user clicks it again.

Any helpful thoughts on the matter?

Answer 1

You should probably do this earlier in the dialog life cycle, like Form_Load. Also, even if you needed to do it here, don’t keep reloading the list. Check to see if the list is already loaded. Otherwise you will wipe out the current selection everytime the user opens the dropdown.