Add reflection helpers

Imported from the SVM ACW for Component-based Architectures

PolyFeed/Helpers/ReflectionHelpers.cs

@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Linq;
+using System.IO;
+
+namespace PolyFeed.Helpers
+{
+	internal static class ReflectionUtilities
+	{
+		public static bool Verbose = true;
+
+		public static IEnumerable<Assembly> IterateLoadedAssemblies()
+		{
+			return AppDomain.CurrentDomain.GetAssemblies();
+		}
+
+		public static IEnumerable<Type> IterateAllLoadedTypes()
+		{
+			return IterateLoadedAssemblies()
+				.SelectMany((Assembly nextAssembly) => nextAssembly.GetTypes());
+		}
+
+		public static IEnumerable<Type> IterateLoadedTypes(Assembly targetAssembly)
+		{
+			return targetAssembly.GetTypes();
+		}
+
+		public static void LoadAssembliesDirectory(string directory)
+		{
+			foreach (string nextDll in Directory.EnumerateFiles(directory, "*.dll"))
+			{
+				AssemblyName assemblyName = AssemblyName.GetAssemblyName(nextDll);
+
+				// Check that a strongname is actually present
+				if (assemblyName.GetPublicKeyToken().Length < 8)
+					continue;
+
+				// Verify the strongname is valid.
+				/*try
+				{
+					bool isOk = false;
+					NativeMethods.StrongNameSignatureVerificationEx(nextDll, 0xFF, ref isOk);
+					if (!isOk)
+						continue;
+				}
+				catch (DllNotFoundException error)
+				{
+					Console.Error.WriteLine($"Warning: Unable to verify the integrity of the StrongName for '{nextDll}' (DLL not found: {error.Message}).");
+				}*/
+
+				try
+				{
+					Assembly.LoadFrom(nextDll);
+					// FUTURE: Consider using Assembly.ReflectionOnlyLoadFrom in a separate AppDomain to figure out if there's anything useful in an assembly before loading it for reals
+				}
+				catch (BadImageFormatException error)
+				{
+					if (Verbose) Console.Error.WriteLine($"Error loading '{nextDll}': {error.Message}");
+				}
+			}
+		}
+
+
+		/// <summary>
+		/// Searches the types present in the specified assembly to find a type that implements 
+		/// the specified interface.
+		/// </summary>
+		/// <param name="targetInterface">The target interface that returned types should implement.</param>
+		/// <param name="assemblyToSearch">The assembly to search through for matching types.</param>
+		public static IEnumerable<Type> IterateImplementingTypes(Type targetInterface, Assembly assemblyToSearch)
+		{
+			if (!targetInterface.IsInterface)
+				throw new ArgumentException($"Error: The specified type {targetInterface} is not an " +
+					"interface, so it can't be used to search for implementing types.");
+
+			// FUTURE: Add caching here? Reflection is slow
+			foreach (Type nextType in IterateAllLoadedTypes())
+			{
+				// Make sure it implements the specified interface
+				if (!targetInterface.IsAssignableFrom(nextType))
+					continue;
+
+				yield return nextType;
+			}
+		}
+	}
+}

PolyFeed/PolyFeed.csproj

@@ -151,6 +151,7 @@
     <Compile Include="SnakeCasePropertySelector.cs" />
     <Compile Include="Helpers\HtmlHelpers.cs" />
     <Compile Include="Helpers\UserAgentHelper.cs" />
+    <Compile Include="Helpers\ReflectionHelpers.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />