c# keypress listening in background

private void button1_Click(object sender, EventArgs e)
{
    Keys 开发者_如何学Pythonkey = new Keys();
    while (true)
    {
        if (key == Keys.F5)
        {
            MessageBox.Show("F5");
        }
        else if (key == Keys.F4)
        {
            MessageBox.Show("F4");
        }
    }
}

How can I make this run in the background when the form is out of focus? My ultimate goal is to make this run in the background, and wait for the F5/F4 key to be pressed.

I'm not entirely sure what your question is. If you want to register a global hotkey you can use the windows api function RegisterHotKey.
There are already a few questions on SO answering how to use this function in C#.

If you want a hot-key that's only active on a certain control or form you can use the events supplied by WinForms.

If you want to be notifed of all key-presses on the desktop then a low level keyboard hook is appropriate. But don't use a hook if you just want a global hotkey.

Your code itself doesn't make much sense. new Keys() just returns the default value of the Keys enum(Keys.None I guess) which is never equal to F4 or F5.

Not sure what the relationship is between the button1 and keypress, but take a look at the KeyPressEventHandler

Code example below, displays the last key pressed:

    private void button1_Click(object sender, EventArgs e)
    {
        this.textBox1.KeyPress += new KeyPressEventHandler(keypressed);
    }

    private void keypressed(Object o, KeyPressEventArgs e)
    {
        label1.Text = e.KeyChar.ToString();
    }