Enum.IsDefine源碼

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");    }    Type type = value.GetType();    if (!(type is RuntimeType))    {        throw new ArgumentException(Environment.GetResourceString("Arg_MustBeType"), "valueType");    }    Type underlyingType = GetUnderlyingType(enumType);    if (type.IsEnum)    {        Type type3 = GetUnderlyingType(type);        if (type != enumType)        {            throw new ArgumentException(string.Format(Environment.GetResourceString("Arg_EnumAndObjectMustBeSameType"), type.ToString(), enumType.ToString()));        }        type = type3;    }    else if ((type != underlyingType) && (type != stringType))    {        throw new ArgumentException(string.Format(Environment.GetResourceString("Arg_EnumUnderlyingTypeAndObjectMustBeSameType"), type.ToString(), underlyingType.ToString()));    }    if (type == stringType)    {        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;    if ((((type != intType) && (type != typeof(short))) && ((type != typeof(ushort)) && (type != typeof(byte)))) && (((type != typeof(sbyte)) && (type != typeof(uint))) && ((type != typeof(long)) && (type != typeof(ulong)))))    {        throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_UnknownEnumType"));    }    ulong num2 = ToUInt64(value);    return (BinarySearch(values, num2) >= 0);}