c# - GetInterfaces() 返回 FullName = null 的通用接口(interface)类型

Question

谁能向我解释为什么下面代码中的 GetInterfaces() 会返回一个 FullName = null 的接口(interface)类型？

public class Program
{
    static void Main(string[] args)
    {
        Type[] interfaces = typeof (Data<>).GetInterfaces();
        foreach (Type @interface in interfaces)
        {
            Console.WriteLine("Name='{0}' FullName='{1}'", @interface.Name, @interface.FullName ?? "null");
        }
    }
}

public class Data<T> : IData<T>
{
    public T Content { get; set; }
}

public interface IData<T>
{
    T Content { get; set; }
}

程序的输出是:

Name=IData`1' FullName='null'

我有点期待:

Name=IData`1'
FullName='ConsoleApplication2.IData`1'

请赐教:)

Answer 1

https://learn.microsoft.com/archive/blogs/haibo_luo/type-fullname-returns-null-when

Update: Microsoft documentation is improved:

https://msdn.microsoft.com/en-us/library/system.type.fullname.aspx

Type.FullName is null if the current instance represents a generic type parameter, an array type, pointer type, or byref type based on a type parameter, or a generic type that is not a generic type definition but contains unresolved type parameters.

这是从文档中归纳出的 Type.FullName 为 null 的示例:

    [Fact]
    public void FullNameOfUnresolvedGenericArgumentIsNull()
    {
        Type openGenericType = typeof(Nullable<>);
        Type typeOfUnresolvedGenericArgument = openGenericType.GetGenericArguments()[0];

        Assert.Null(typeOfUnresolvedGenericArgument.FullName);
    }