System.Enum.IsDefined C# (CSharp) Метод

        public static bool IsDefined(Type enumType, Object value)
        {
            if (enumType == null)
                throw new ArgumentNullException("enumType");

            if (!(enumType is RuntimeType))
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBeType"), "enumType");

            if (!enumType.IsEnum)
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBeEnum"), "enumType");

            if (value == null)
                throw new ArgumentNullException("value");

            // Check if both of them are of the same type
            Type valueType = value.GetType();

            if (!(valueType is RuntimeType))
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBeType"), "valueType");

            Type underlyingType = GetUnderlyingType(enumType);

            // If the value is an Enum then we need to extract the underlying value from it
            if (valueType.IsEnum)
            {
                Type valueUnderlyingType = GetUnderlyingType(valueType);

                if (valueType != enumType)
                    throw new ArgumentException(String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("Arg_EnumAndObjectMustBeSameType"), valueType.ToString(), enumType.ToString()));

                valueType = valueUnderlyingType;
            }
            else
                // The value must be of the same type as the Underlying type of the Enum
                if ((valueType != underlyingType) && (valueType != stringType))
            {
                throw new ArgumentException(String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("Arg_EnumUnderlyingTypeAndObjectMustBeSameType"), valueType.ToString(), underlyingType.ToString()));
            }

            // If String is passed in
            if (valueType == stringType)
            {
                // Get all of the Fields
                String[] names = GetHashEntry(enumType).names;

                for (int i = 0; i < names.Length; i++)
                    if (names[i].Equals((string)value))
                        return true;

                return false;
            }

            ulong[] values = GetHashEntry(enumType).values;

            // Look at the 8 possible enum base classes
            if (valueType == intType || valueType == typeof(short) || valueType == typeof(ushort) || valueType == typeof(byte) || valueType == typeof(sbyte) || valueType == typeof(uint) || valueType == typeof(long) || valueType == typeof(ulong))
            {
                ulong val = ToUInt64(value);

                return (BinarySearch(values, val) >= 0);
            }

            BCLDebug.Assert(false, "Unknown enum type");
            throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_UnknownEnumType"));
        }
        

        public EnumOrString(T value)
        {
            Contract.Requires(SystemEnum.IsDefined(typeof(T), value));

            m_enum   = value;
            m_string = null;
        }