how not to allow multiple keystokes received at one key press?

Question

when we press a key and keep pressing it the keypress and keydown event continuously fires. Is there a way to let these fire only after a complete cycle ,eg keydown and the

Answer 1

You can do it application-wide by filtering the key down messages with IMessageFilter. Here's an example:

  public partial class Form1 : Form, IMessageFilter {
    public Form1() {
      InitializeComponent();
      Application.AddMessageFilter(this);
      this.FormClosed += (s, e) => Application.RemoveMessageFilter(this);
    }

    private Keys mLastKey = Keys.None;

    public bool PreFilterMessage(ref Message m) {
      if (m.Msg == 0x100 || m.Msg == 0x104) {
        // Detect WM_KEYDOWN, WM_SYSKEYDOWN
        Keys key = (Keys)m.WParam.ToInt32();
        if (key != Keys.Control && key != Keys.Shift && key != Keys.Alt) {
          if (key == mLastKey) return true;
          mLastKey = key;
        }
      }
      else if (m.Msg == 0x101 || m.Msg == 0x105) {
        // Detect WM_UP, WM_SYSKEYUP
        Keys key = (Keys)m.WParam.ToInt32();
        if (key == mLastKey) mLastKey = Keys.None;
      }
      return false;
    }
  }

One thing I pursued is the repeat count in the WM_KEYDOWN message. Oddly this didn't work on my machine, it was 1 for repeating keys. Not sure why.