public static void AddAssembly(this HttpConfiguration httpConfiguration, Assembly assembly) { Dispatcher.IAssembliesResolver existingAssembliesResolver = GetAssembliesResolver(httpConfiguration); ICollection <Assembly> existingAssemblies = existingAssembliesResolver.GetAssemblies(); if (!existingAssemblies.Contains(assembly)) { AssembliesResolver assembliesResolver = new AssembliesResolver(existingAssemblies); assembliesResolver.Add(assembly); httpConfiguration.Services.Replace(typeof(Dispatcher.IAssembliesResolver), assembliesResolver); } }