Can you use “where” to require an attribute in c#?

问题

I want to make a generic class that accepts only serializable classes, can it be done with the where constraint?

The concept I\'m looking for is this:

public class MyClass<T> where T : //[is serializable/has the serializable attribute]

回答1:

Nope, I'm afraid not. The only things you can do with constraints are:

where T : class - T must be a reference type
where T : struct - T must be a non-nullable value type
where T : SomeClass - T must be SomeClass or derive from it
where T : ISomeInterface - T must be ISomeInterface or implement it
where T : new() - T must have a public parameterless constructor

Various combinations are feasible, but not all. Nothing about attributes.

回答2:

What I know; you can not do this. Have you though about adding an 'Initialize' method or something similar?

public void Initialize<T>(T obj)
{
     object[] attributes = obj.GetType().GetCustomAttributes(typeof(SerializableAttribute));
     if(attributes == null || attributes.Length == 0)
          throw new InvalidOperationException("The provided object is not serializable");
}

I haven't tested this code, but I hope that you get my point.

回答3:

Afraid not. Best you can do is a runtime check on Type.IsSerializable.

回答4:

If you are looking for any class that is serializable, I think you are out of luck. If you are looking for objects that you have created, you could create a base class that is serializable and have every class you want to support derive from it.

回答5:

I know this is old, but I am using a static constructor to check. It is later but allows you to throw an error at runtime.

来源：https://stackoverflow.com/questions/221687/can-you-use-where-to-require-an-attribute-in-c

标签

generics

attributes

constraints

where