MVVM Light push/pop message for parameter passing - mvvm-light

Question

A question for Laurent and others.
I've added extension functions to the MVVM Light messenger to push and pop messages. The idea is that when a viewmodel needs to open another view/viewmodel, it would push the parameters from the message stack and then the newly opened viewmodel (or possibly the viewmodellocator) would subscribe to the message and pop the message to get the parameters. I'm looking for feedback on this idea. The code is posted below.
MVVMlightMessengerStackExtension.cs (code below has been updated since the original post to clean things up a bit and be more consistent with stack behavior)
namespace GalaSoft.MvvmLight.Messaging
{
public static class MessageHelper
{
/// <summary>
/// Store a list of all the pushed messages
/// </summary>
private static List<Tuple<int, object, object>> _q = new List<Tuple<int, object, object>>();
private static int _q_idx = Int32.MaxValue; // SL has no SortedList or SortedDictionary so keep an index the of the list to push/pops are in order
/// <summary>
/// Push a message for later retrival. Typically by a viewmodel constructor.
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
/// <param name="message"></param>
/// <param name="token"></param>
[DebuggerStepThrough()]
public static void Push<TMessage>(this Messenger M, TMessage message, object token = null)
{
Monitor.Enter(_q);
try
{
_q.Add(Tuple.Create<int, object, object>(_q_idx--, message, token));
}
finally
{
Monitor.Exit(_q);
}
}
/// <summary>
/// Send a stored/delayed message
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
[DebuggerStepThrough()]
public static void PopAndSend<TMessage>(this Messenger M, object token = null)
{
TMessage mesg = M.Pop<TMessage>(token);
if (token != null)
M.Send(mesg, token);
else
M.Send(mesg);
}
/// <summary>
/// Pop a stored/delayed message
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
[DebuggerStepThrough()]
public static TMessage Pop<TMessage>(this Messenger M, object token = null)
{
Monitor.Enter(_q);
try
{
var result = _q.OrderBy(a => a.Item1).FirstOrDefault(a => a.Item2 is TMessage && a.Item3 == token);
if (result == null)
throw new InvalidOperationException("The stack is empty.");
_q.Remove(result);
return (TMessage)result.Item2;
}
finally
{
Monitor.Exit(_q);
}
}
/// <summary>
/// Peek at a stored/delayed message
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
[DebuggerStepThrough()]
public static TMessage Peek<TMessage>(this Messenger M, object token = null)
{
Monitor.Enter(_q);
try
{
var result = _q.OrderBy(a => a.Item1).FirstOrDefault(a => a.Item2 is TMessage && a.Item3 == token);
if (result == null)
throw new InvalidOperationException("The stack is empty.");
return (TMessage)result.Item2;
}
finally
{
Monitor.Exit(_q);
}
}
/// <summary>
/// Clear the stack
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
[DebuggerStepThrough()]
public static void Clear(this Messenger M)
{
Monitor.Enter(_q);
try
{
_q.Clear();
}
finally
{
Monitor.Exit(_q);
}
}
/// <summary>
/// Clear the stack
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="M"></param>
[DebuggerStepThrough()]
public static void Clear<TMessage>(this Messenger M)
{
Monitor.Enter(_q);
try
{
var delList = _q.Where(a => a.Item2 is TMessage);
foreach (var item in delList)
_q.Remove(item);
}
finally
{
Monitor.Exit(_q);
}
}
}
}

Answer 1

I have a somewhat similar concept in my backlog, very interesting implementation here. I will bookmark it and come back to it when the time comes.
Cheers and thanks for sharing!
Laurent