How to determine whether the parameters of the method are allowed to be empty?

[NMSAzulX]

e.g.

public class Test{

public void Show1(string name){}

public void Show2(string? name){}
}

I did some experiments and found that PatameterInfo has no attribute to express that the parameter can be empty.
Is there any good idea?

[Clockwork-Muse]

If you mean "express that the parameter can be null ", then it's apparently done as an attribute.

[svick]

And if you look at the answer below that, you'll learn that .Net 6 has an API for that.

[NMSAzulX]

Thank you! It works. Can this method detect string?[] is there a null reference? GenericType or ElementType.

[NMSAzulX]

And if you look at the answer below that, you'll learn that .Net 6 has an API for that.

This API is really easy to use. But I'm working on netcore3.1 and 5. 0 compatibility, so I need another way. Do you have any suggestions?

[huoyaoyuan]

There isn't OOB package shipped, so you have to port the code manually.

[NMSAzulX]

Now, I have to port the source code and comment out some internal code. I'm not sure what problems this will cause. The three classes migrated to 3.1 or 5.0 are: NullabilityInfo ,NullabilityInfoContext, NullabilityState

Comment out some internal code

 private static MemberInfo GetMemberMetadataDefinition(MemberInfo member)
 {
        //Type? type = member.DeclaringType;
        //if ((type != null) && type.IsGenericType && !type.IsGenericTypeDefinition)
        //{
        //    return type.GetGenericTypeDefinition().GetMemberWithSameMetadataDefinitionAs(member);
       //}
       return member;
}

[Xyncgas]

The IDE highlights stuffs.
For example if you are assigning null to T instead of T?
But if you ignore it when IDE warns you or if you are using command lines to compile then it's going to compile as of 2021.

[Xyncgas]

Unless you use if check you can't ensure it's null.
maybe I am missing something here though, because I heard about System.Nullable and how you can use HasValue to check

[Clockwork-Muse]

In context, OP appears to be using reflection to extract information about methods - there's not going to be an IDE involved, and since the method itself is not being executed there's no way to check HasValue either.

[NMSAzulX]

Yes. Now I'm going to pause some work on nullable reference reflection because it's hard to reflect, such as method's return values, passing in generics, and so on.