C#：Activeになっているウィンドウのアプリケーション名を取得する

GetForegroundWindowProductName.cs

[DllImport("user32.dll")]
public static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll", EntryPoint = "GetWindowText", CharSet = CharSet.Auto)]
public static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

[DllImport("user32.dll")]
private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);

int processid;

try{
    GetWindowThreadProcessId(GetForegroundWindow(), out processid);
    if (0 != processid){
        Process p = Process.GetProcessById(processid);
        System.Diagnostics.Debug.Write(processid + ":");
        System.Diagnostics.Debug.WriteLine(p.MainModule.FileVersionInfo.ProductName);//アプリケーションの名前が出てきます
    }
    else{
        System.Diagnostics.Debug.Write(processid + ":Sleep");
    }
}
catch (System.ComponentModel.Win32Exception e){
    System.Diagnostics.Debug.Writeln("何もしない");
}