Allow assembly hot replacement from stream

ILSpy/AssemblyList.cs

@@ -145,6 +145,29 @@ namespace ICSharpCode.ILSpy
 			}
 			return newAsm;
 		}
+
+		/// <summary>
+		/// Replace the assembly object model from a crafted stream, without disk I/O
+		/// Returns null if it is not already loaded.
+		/// </summary>
+		public LoadedAssembly HotReplaceAssembly(string file, Stream stream)
+		{
+			App.Current.Dispatcher.VerifyAccess();
+			file = Path.GetFullPath(file);
+
+			var target = this.assemblies.FirstOrDefault(asm => file.Equals(asm.FileName, StringComparison.OrdinalIgnoreCase));
+			if (target == null)
+				return null;
+
+			var index = this.assemblies.IndexOf(target);
+			var newAsm = new LoadedAssembly(this, file, stream);
+			lock (assemblies)
+			{
+				this.assemblies.Remove(target);
+				this.assemblies.Insert(index, newAsm);
+			}
+			return newAsm;
+		}
 		
 		public void Unload(LoadedAssembly assembly)
 		{

ILSpy/LoadedAssembly.cs

@@ -35,7 +35,7 @@ namespace ICSharpCode.ILSpy
 		readonly string fileName;
 		readonly string shortName;
 		
-		public LoadedAssembly(AssemblyList assemblyList, string fileName)
+		public LoadedAssembly(AssemblyList assemblyList, string fileName, Stream stream = null)
 		{
 			if (assemblyList == null)
 				throw new ArgumentNullException("assemblyList");
@@ -44,7 +44,7 @@ namespace ICSharpCode.ILSpy
 			this.assemblyList = assemblyList;
 			this.fileName = fileName;
 			
-			this.assemblyTask = Task.Factory.StartNew<ModuleDefinition>(LoadAssembly); // requires that this.fileName is set
+			this.assemblyTask = Task.Factory.StartNew<ModuleDefinition>(LoadAssembly, stream); // requires that this.fileName is set
 			this.shortName = Path.GetFileNameWithoutExtension(fileName);
 		}
 		
@@ -93,12 +93,26 @@ namespace ICSharpCode.ILSpy
 			get { return assemblyTask.IsFaulted; }
 		}
 		
-		ModuleDefinition LoadAssembly()
+		ModuleDefinition LoadAssembly(object state)
 		{
+			var stream = state as Stream;
+			ModuleDefinition module;
+
 			// runs on background thread
 			ReaderParameters p = new ReaderParameters();
 			p.AssemblyResolver = new MyAssemblyResolver(this);
-			ModuleDefinition module = ModuleDefinition.ReadModule(fileName, p);
+
+			if (stream != null)
+			{
+				// Read the module from a precrafted stream
+				module = ModuleDefinition.ReadModule(stream, p);
+			}
+			else
+			{
+				// Read the module from disk (by default)
+				module = ModuleDefinition.ReadModule(fileName, p);
+			}
+
 			if (DecompilerSettingsPanel.CurrentDecompilerSettings.UseDebugSymbols) {
 				try {
 					LoadSymbols(module);