Added support for .NET 4.0

Author: ENikS

src/Extensions/Reflection/IntrospectionExtensions.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 
 namespace System.Reflection
@@ -35,6 +36,8 @@ internal TypeInfo(Type type)
 
         public Type AsType() => _type;
 
+        public bool IsAssignableFrom(Type type) => _type.IsAssignableFrom(type);
+
         public bool IsAssignableFrom(TypeInfo typeInfo) => _type.IsAssignableFrom(typeInfo.AsType());
 
         public bool IsGenericParameter => _type.IsGenericParameter;
@@ -195,6 +198,14 @@ public override bool Equals(object obj)
     internal static class IntrospectionExtensions
     {
 #if NET40
+
+        public static Attribute GetCustomAttribute(this ParameterInfo info, Type type)
+        {
+            return info.GetCustomAttributes(type, true)
+                       .Cast<Attribute>()
+                       .FirstOrDefault();
+        }
+
         public static TypeInfo GetTypeInfo(this Type type)
         {
             if (type == null)