namespace System.Web.ModelBinding {
    using System;
    using System.Linq;
 
    internal static class TypeHelpers {
 
        public static Type ExtractGenericInterface(Type queryType, Type interfaceType) {
            Func<Type, bool> matchesInterface = t => t.IsGenericType && t.GetGenericTypeDefinition() == interfaceType;
            return (matchesInterface(queryType)) ? queryType : queryType.GetInterfaces().FirstOrDefault(matchesInterface);
        }
 
        public static Type[] GetTypeArgumentsIfMatch(Type closedType, Type matchingOpenType) {
            if (!closedType.IsGenericType) {
                return null;
            }
 
            Type openType = closedType.GetGenericTypeDefinition();
            return (matchingOpenType == openType) ? closedType.GetGenericArguments() : null;
        }
 
        public static bool IsCompatibleObject(Type type, object value) {
            return ((value == null && TypeAllowsNullValue(type)) || type.IsInstanceOfType(value));
        }
 
        public static bool IsNullableValueType(Type type) {
            return Nullable.GetUnderlyingType(type) != null;
        }
 
        public static bool TypeAllowsNullValue(Type type) {
            return (!type.IsValueType || IsNullableValueType(type));
        }
 
    }
}