Use SessionMessageType for WebSocket messages

MediaBrowser.Model/Net/WebSocketMessage.cs

@@ -2,6 +2,7 @@
 #pragma warning disable CS1591
 
 using System;
+using MediaBrowser.Model.Session;
 
 namespace MediaBrowser.Model.Net
 {
@@ -15,7 +16,7 @@ namespace MediaBrowser.Model.Net
         /// Gets or sets the type of the message.
         /// </summary>
         /// <value>The type of the message.</value>
-        public string MessageType { get; set; }
+        public SessionMessageType MessageType { get; set; }
 
         public Guid MessageId { get; set; }
 

MediaBrowser.Model/Session/SessionMessageType.cs

@@ -0,0 +1,50 @@
+#pragma warning disable CS1591
+
+namespace MediaBrowser.Model.Session
+{
+    /// <summary>
+    /// The different kinds of messages that are used in the WebSocket api.
+    /// </summary>
+    public enum SessionMessageType
+    {
+        // Server -> Client
+        ForceKeepAlive,
+        GeneralCommand,
+        UserDataChanged,
+        Sessions,
+        Play,
+        SyncPlayCommand,
+        SyncPlayGroupUpdate,
+        PlayState,
+        RestartRequired,
+        ServerShuttingDown,
+        ServerRestarting,
+        LibraryChanged,
+        UserDeleted,
+        UserUpdated,
+        SeriesTimerCreated,
+        TimerCreated,
+        SeriesTimerCancelled,
+        TimerCancelled,
+        RefreshProgress,
+        ScheduledTaskEnded,
+        PackageInstallationCancelled,
+        PackageInstallationFailed,
+        PackageInstallationCompleted,
+        PackageInstalling,
+        PackageUninstalled,
+        ActivityLogEntry,
+        ScheduledTasksInfo,
+
+        // Client -> Server
+        ActivityLogEntryStart,
+        ActivityLogEntryStop,
+        SessionsStart,
+        SessionsStop,
+        ScheduledTasksInfoStart,
+        ScheduledTasksInfoStop,
+
+        // Shared
+        KeepAlive,
+    }
+}