How to intercept the TAB key press to prevent standard focus change in C#

Question

Normally when pressing the TAB key you change the focus to the next control in the given tab order. I would like to prevent that and have the TAB key do something else. In my case I'd like to change focus from a combobox to a completely different control. I can't do this by setting the tab order. I need to do this programatically. Any idea how? It seems like the KeyDown and KeyPress events can't handle TAB key correctly. Thanks.

Answer 1

覆盖表单上的ProcessDialogKey或ProcessTabKey ，并根据所关注的控件执行所需的逻辑。

Answer 2

Based on JRS's suggestion of using the PreviewKeyDown event, this sends the key press through to the control:

private void textBox1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
{
    if (e.KeyCode == Keys.Tab)
        e.IsInputKey = true;
}

Then you can handle the control's KeyDown event if you want to customise the behaviour:

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.Tab)
    {
        MessageBox.Show("The tab key was pressed while holding these modifier keys: "
                + e.Modifiers.ToString());
    }
}

---

TextBoxBase alternative

If the control is derived from TextBoxBase (ie TextBox or RichTextBox ), with the Multiline property set to true , then you can simply set the AcceptsTab property to true .

TextBoxBase.AcceptsTab Property

Gets or sets a value indicating whether pressing the TAB key in a multiline text box control types a TAB character in the control instead of moving the focus to the next control in the tab order.

Answer 3

Override the control's LostFocus event see link below for examples:

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.lostfocus.aspx

Answer 4

You can try this code on your KeyDown event:

if (e.KeyCode == Keys.Tab) {
  //your logic
  e.SuppressKeyPress = true;
}

If the button clicked is Tab, then do any custom logic you want, then call SuppressKeyPress to stop the KeyPress event from firing and invoking the normal Tab logic for you.

Answer 5

Since I am building a UserControl, I ended up using the PreviewKeyDown event on the control. This avoids having to handle key press events on the host form.

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.previewkeydown.aspx