How can i invoke helpprovider without pressing F1?

Assuming it is a chm-file you want to show, you should use System.Windows.Forms.Help

So listen to a key stroke, and show your chm-file:

void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.H)
        Help.ShowHelp(this, "my.chm");
}

If you wanted to listen for a key stroke globally, than look at this: Processing Global Mouse and Keyboard Hooks in C#