Check if AppDomain is already unloaded before accessing. (#54)

* Check if AppDomain is already unloaded before accessing. Fixes #51 * Bump package release version to 1.1.13
jthelin · Oct 13, 2018 · 2c5782d · 2c5782d
1 parent 413799a
commit 2c5782d
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Showing 2 changed files with 33 additions and 10 deletions.
diff --git a/ServerHost/ServerHost.cs b/ServerHost/ServerHost.cs
@@ -103,12 +103,14 @@ public static ServerHostHandle<TServer> LoadServerInNewAppDomain<TServer>(
         [SuppressMessage("ReSharper", "MemberCanBePrivate.Global")]
         public static void UnloadServerInAppDomain(AppDomain appDomain)
         {
-            if (appDomain == null) return;
+            if (appDomain == null || appDomain.IsUnloaded()) return;
 
             string appDomainName = "UNKNOWN";
 
             try
             {
+                // We may get AppDomainUnloadedException thrown here - X-ref: #46.
+
                 appDomainName = appDomain.FriendlyName;
 
                 appDomain.UnhandledException -= ReportUnobservedException;
@@ -138,20 +140,21 @@ public static void UnloadAllServers()
                 {
                     if (appDomain == null) continue;
 
-                    string appDomainName = null;
-                    try
+                    if (appDomain.IsUnloaded())
                     {
-                        // We may get AppDomainUnloadedException thrown here - X-ref: #46.
-
-                        appDomainName = appDomain.FriendlyName;
+                        Log.Debug($"AppDomain for server {serverName} has already been unloaded.");
+                        continue;
+                    }
 
-                        Log.Info($"Unloading Server {serverName} in AppDomain {appDomainName}");
+                    try
+                    {
+                        Log.Info($"Unloading AppDomain for server {serverName}.");
 
                         UnloadServerInAppDomain(appDomain);
                     }
                     catch (Exception exc)
                     {
-                        Log.Warn($"Ignoring error unloading AppDomain {appDomainName ?? serverName}. " + exc.Message, exc);
+                        Log.Warn($"Ignoring error unloading AppDomain for server {serverName}. " + exc.Message, exc);
                     }
                 }
             }
@@ -161,7 +164,7 @@ public static void UnloadAllServers()
         /// Construct AppDomain configuration metadata based on the current execution environment.
         /// </summary>
         /// <returns>AppDomainSetup info for creating an new child AppDomain.</returns>
-        private static AppDomainSetup GetAppDomainSetupInfo()
+        public static AppDomainSetup GetAppDomainSetupInfo()
         {
             AppDomain currentAppDomain = AppDomain.CurrentDomain;
 
@@ -190,5 +193,25 @@ private static void ReportUnobservedException(object sender, UnhandledExceptionE
             Exception exception = (Exception) eventArgs.ExceptionObject;
             Log.Warn("Unobserved exception: " + exception);
         }
+
+        /// <summary>
+        /// Check whether the specified AppDomain has already been unloaded and is now inaccessible.
+        /// </summary>
+        /// <returns> Returns <c>true</c> if the specified AppDomain has been unloaded.</returns>
+        /// <param name="appDomain"> The AppDomain to be checked. </param>
+        private static bool IsUnloaded(this AppDomain appDomain)
+        {
+            try
+            {
+                string unused = appDomain.FriendlyName;
+
+                // If this worked, then the AppDomain is still accessible.
+                return false;
+            }
+            catch (AppDomainUnloadedException)
+            {
+                return true;
+            }
+        }
     }
 }
diff --git a/ServerHost/ServerHost.csproj b/ServerHost/ServerHost.csproj
@@ -11,7 +11,7 @@
 
   <PropertyGroup>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
-    <Version>1.1.12</Version>
+    <Version>1.1.13</Version>
     <Authors>Jorgen Thelin</Authors>
     <Copyright>Copyright © Jorgen Thelin 2015-2018</Copyright>
     <Description>ServerHost - A .NET Server Hosting utility library, including in-process server host testing.</Description>