void Main()
{
  // in case of non 64 bit system change "Program Files (x86)" to "Program Files"
  string net40Dir = @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\";
  string net45Dir = @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\";

  // 1. Get all types from all xml doc files in both directories that are containing .NET assemblies and group them by assemblies
  var net40Grouped = GetPublicTypesByAssembly(net40Dir);
  var net45Grouped = GetPublicTypesByAssembly(net45Dir);

  // 2. Get list of newly added assemblies
  var newAssemblies = net45Grouped.Where(kvp => !net40Grouped.ContainsKey(kvp.Key)).ToList();
  Console.WriteLine("New assemblies in .NET 4.5 Beta: (total count - {0})", newAssemblies.Count);
  newAssemblies.ForEach(kvp => Console.WriteLine(kvp.Key));

  Console.WriteLine();

  // 3. Get all assemblies that are not present in .NET 4.5 beta
  var nonExistentAssemblies = net40Grouped.Where(kvp => !net45Grouped.ContainsKey(kvp.Key)).ToList();

  Console.WriteLine("Assemblies that are not present in .NET 4.5 Beta folder comparing to .NET 4.0: (total count - {0})", nonExistentAssemblies.Count);
  nonExistentAssemblies.ForEach(kvp => Console.WriteLine(kvp.Key));

  Console.WriteLine();

  // 4. Get all new types in .NET 4.0 and .NET 4.5 Beta assemblies
  var net40 = net40Grouped.SelectMany(kvp => kvp.Value).ToList();
  var net45 = net45Grouped.SelectMany(kvp => kvp.Value).ToList();

  var newTypes = net45.Except(net40).ToList();
  Console.WriteLine("Types count in .NET 4.0:|{0}", net40.Count);
  Console.WriteLine("Types count in .NET 4.5 Beta:|{0}", net45.Count);
  Console.WriteLine("New types count in .NET 4.5 Beta comparing to .NET 4.0:|{0}", newTypes.Count);

  // 5. Get assemblies that are containing new types
  var assembliesWithChanges = net45Grouped.Where(kvp => newTypes.Any(type => kvp.Value.ContainsValue(type.Value)));

  // 6. Remove existent in .NET 4.0 types from assembliesWithChanges to get clear lists of new types grouped by assemblies
  var newTypesGrouped = assembliesWithChanges
      .ToDictionary(typesGroup => typesGroup.Key, typesGroup => typesGroup.Value.Except(net40)
      .Select(kvp => kvp.Value).ToList());

  Console.WriteLine("New types by assembly:");
  foreach (var assemblyWithNewTypes in newTypesGrouped)
  {
      Console.WriteLine("{0}|{1}", assemblyWithNewTypes.Key, assemblyWithNewTypes.Value.Count);
      foreach (var typeName in assemblyWithNewTypes.Value)
      {
          Console.WriteLine(typeName);
      }
      Console.WriteLine();
  }
}

Dictionary<string, Dictionary<int, string>> GetPublicTypesByAssembly(string xmlDocsDirectory)
{
  string[] xmlDocFiles = Directory.GetFiles(xmlDocsDirectory, "*.xml");
  var result = new Dictionary<string, Dictionary<int, string>>();

  foreach (var xmlDoc in xmlDocFiles)
  {
      var root = XDocument.Load(xmlDoc).Root;
      if (root == null) continue;

      var members = root.Element("members");
      if (members == null) continue;

      var typesByAssembly = members.Elements("member")
          .Where(e => e.Attribute("name").Value.StartsWith("T:"))
          .ToDictionary(e => e.Attribute("name").Value.GetHashCode(), e => e.Attribute("name").Value.Substring(2) /* T: */);

      result.Add(Path.GetFileNameWithoutExtension(xmlDoc) + ".dll", typesByAssembly);
  }

  return result;
}