I'm generally a VB guy, but this seems to work for me as demo code, using the form itself as the input source:
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
private bool _keyHeld;
public Form1()
{
InitializeComponent();
this.KeyUp += new KeyEventHandler(Form1_KeyUp);
this.KeyDown += new KeyEventHandler(Form1_KeyDown);
this._keyHeld = false;
}
void Form1_KeyUp(object sender, KeyEventArgs e)
{
this._keyHeld = false;
}
void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (!this._keyHeld)
{
this._keyHeld = true;
if (this.BackColor == Control.DefaultBackColor)
{
this.BackColor = Color.Red;
}
else
{
this.BackColor = Control.DefaultBackColor;
}
}
else
{
e.Handled = true;
}
}
}
}
I think the logic gets a little sketchy if you're holding down multiple keys at a time, but that seems to only fire the event from the last key that was pressed anyway, so I don't think it becomes an issue.
I tested this in a TextBox in VB, and it worked fine. Wasn't sure on the inheritance conventions I should follow in c#, so I left it as a straight Form for this answer.
Apologies for any gross code formatting errors, again, this isn't my usual language.