After reading a lot, I separated my code into two cases, for metro application and all other applications. 
My solution handle the exception I got for metro applications and exceptions I got regarding the platform.
This is the code that finally worked:
[DllImport("user32.dll")]
public static extern IntPtr GetForegroundWindow();
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
[DllImport("user32.dll")]
static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);
public string GetActiveWindowTitle()
{
    var handle = GetForegroundWindow();
    string fileName = "";
    string name = "";
    uint pid = 0;
    GetWindowThreadProcessId(handle, out pid);
    Process p = Process.GetProcessById((int)pid);
    var processname = p.ProcessName;
    switch (processname)
    {
        case "explorer": //metro processes
        case "WWAHost":
            name = GetTitle(handle);
            return name;
        default:
            break;
    }
    string wmiQuery = string.Format("SELECT ProcessId, ExecutablePath FROM Win32_Process WHERE ProcessId LIKE '{0}'", pid.ToString());
    var pro = new ManagementObjectSearcher(wmiQuery).Get().Cast<ManagementObject>().FirstOrDefault();
    fileName = (string)pro["ExecutablePath"];
    // Get the file version
    FileVersionInfo myFileVersionInfo = FileVersionInfo.GetVersionInfo(fileName);
    // Get the file description
    name = myFileVersionInfo.FileDescription;
    if (name == "")
        name = GetTitle(handle);
 return name;
}
public string GetTitle(IntPtr handle)
{
string windowText = "";
    const int nChars = 256;
    StringBuilder Buff = new StringBuilder(nChars);
    if (GetWindowText(handle, Buff, nChars) > 0)
    {
        windowText = Buff.ToString();
    }
    return windowText;
}