I want to be able to play/pause/next/back the tracks in whatever media
player app is running. So if iTunes is running, it will receive those
commands, if Windows Media Player is, it will receive those commands,
and so on, just like my multimedia keyboard does. I can't find any way
to do this. I have tried sending:
System.Windows.Forms.Keys.MediaPlayPause,
System.Windows.Forms.Keys.MediaPreviousTrack, ect.
but it didn't do anything. Is there a way to send a key that will
control any open media player app, or do I have to have my app check
all the open apps and use the appropriate method for each app to
control it? Any suggestions? Thanks.
SendKeys would work if the media keys were supported, but they're not.
Instead, you can call SendInput() yourself by P/Invoking. Here's a short but
complete sample as a console application. It uses .NET 3.5 and LINQ, but
this is just for convenience and you should have no trouble adapting it to
.NET 2.0 if required.
using System;
using System.Linq;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using System.ComponentModel;
[StructLayout(LayoutKind.Sequential)]
public struct INPUT {
public int type;
public INPUTUNION inputUnion;
}
[StructLayout(LayoutKind.Explicit)]
public struct INPUTUNION {
// Fields
[FieldOffset(0)]
public HARDWAREINPUT hi;
[FieldOffset(0)]
public KEYBDINPUT ki;
[FieldOffset(0)]
public MOUSEINPUT mi;
}
[StructLayout(LayoutKind.Sequential)]
public struct HARDWAREINPUT {
public int uMsg;
public short wParamL;
public short wParamH;
}
[StructLayout(LayoutKind.Sequential)]
public struct KEYBDINPUT {
public short wVk;
public short wScan;
public int dwFlags;
public int time;
public IntPtr dwExtraInfo;
}
[StructLayout(LayoutKind.Sequential)]
public struct MOUSEINPUT {
public int dx;
public int dy;
public int mouseData;
public int dwFlags;
public int time;
public IntPtr dwExtraInfo;
}
static class NativeMethods {
[DllImport("user32.dll", SetLastError = true)]
public static extern int SendInput(int nInputs, [In] INPUT[] pInputs,
int cbSize);
}
class Program {
static int SendKeys(params Keys[] keys) {
var nativeKeys = keys.Select(
k => new INPUT {
type = 1, inputUnion = new INPUTUNION {
ki = new KEYBDINPUT { wVk = (short) k }
}
}
).ToArray();
int keysSent = NativeMethods.SendInput(nativeKeys.Length, nativeKeys,
Marshal.SizeOf(typeof(INPUT)));
if (keysSent == 0) throw new Win32Exception();
return keysSent;
}
static void Main(string[] args) {
while (true) {
var cki = Console.ReadKey();
switch (cki.KeyChar) {
case 'q': Environment.Exit(0); break;
case ' ': SendKeys(Keys.MediaPlayPause); break;
case 'n': SendKeys(Keys.MediaNextTrack); break;
case 'p': SendKeys(Keys.MediaPreviousTrack); break;
case 's': SendKeys(Keys.MediaStop); break;
}
}
}
}
