找出枚举是否设置了“标志”属性

Question

Using reflection, how do I determine whether an enum has the Flags attribute or not

so for MyColor return true

[Flags]
public enum MyColor
{
    Yellow = 1,
    Green = 2,
    Red = 4,
    Blue = 8
}

and for MyTrade return false

public enum MyTrade
{
    Stock = 1,
    Floor = 2,
    Net = 4,
}

Answer 1

if (typeof(MyEnum).GetCustomAttributes(typeof(FlagsAttribute), false).Length > 0)

Answer 2

If you are on .NET 4.5:

if (typeof(MyColor).GetCustomAttributes<FlagsAttribute>().Any())
{
}

Answer 3

If you just want to check if an attribute is present, without inspecting any attribute data, you should use MemberInfo.IsDefined . It returns a bool that indicates "whether one or more attributes of the specified type or of its derived types is applied to this member" instead of dealing with a collection of attributes.

Example

typeof(MyColor).IsDefined(typeof(FlagsAttribute), inherit: false); // true
typeof(MyTrade).IsDefined(typeof(FlagsAttribute), inherit: false); // false

Or, if you're on .NET 4.5+:

using System.Reflection;

typeof(MyColor).IsDefined<FlagsAttribute>(inherit: false); // true
typeof(MyTrade).IsDefined<FlagsAttribute>(inherit: false); // false