C# - Passing focus to a tabcontrol/page and not being able to mousewheel scroll

I have a combobox with four items that correspond to tabs in a tabcontrol. When the user selects an item from the combobox (by left clicking and left clicking again to select an item) the corresponding tabpage in the tabcontrol is selected. The tabpage is set to autoscroll but when the tabpage is selected in this way mousewheel scrolling does not work. (If I click a contr开发者_开发问答ol inside that tabpage manually I can then mousewheel scroll..)

If the user mousewheels to select an item from the same combobox (and successfully passes control to the corresponding tabpage) mousewheel scrolling works fine on that tabpage and I cant figure out why.

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    switch (comboBox1.SelectedIndex)
    {
        case 0:
            tabControl1.SelectedTab = tabPage3;
            tabPage3.Focus();
            break;
    }
    ...
}

I can't get a repro of this problem. Something that might help is to set the focus to the first control of the page instead, just like what happens when you fix the problem by clicking a control. And to do so later, after the combobox event is completed. Use this:

    private void setFocusToPage(TabPage page) {
        var ctl = page.Controls.Count > 0 ? page.Controls[0] : page;
        this.BeginInvoke((MethodInvoker)delegate { ctl.Focus(); });
    }

Call setFocusToPage instead of the Focus() method in your SelectedIndexChanged event handler.