Csharp 如何在C#中判断方法的返回类型是否可以为null(启用了完全可以为null的上下文)

如何判断方法的返回类型是否可以为空？ 项目设置<Nullable>enable</Nullable>是活动的.

一些示例(所有方法都是类型Task或Task<T>)

public sealed class Dto
{
    public int Test { get; set; }
}

public sealed class Dto3
{
    public int? Test { get; set; }
}

public async Task<Dto?> GetSomething()
{
    // This should be found as "Nullable enabled" as the `?` is set.
}

public async Task<Dto3> GetSomething2()
{
    // This should not be found as "Nullable enabled" as the `?` is missing.
}

public async Task<List<Dto>> GetSomething3()
{
    // This should not be found as "Nullable enabled" as the `?` is missing
    // (And the list must be initialized anyways thanks to nullable context).
}

public async Task<List<Dto?>> GetSomething3()
{
    // This should not be found as "Nullable enabled" as the `?` is missing in the first generic type after `Task`.
}

我已经有了遍历搜索名称空间中的类和方法的代码，如下所示:

var assembly = Assembly.GetAssembly(typeof(ISomethingService));

if (assembly is null)
{
    throw new InvalidOperationException("This should never happen");
}

var classes = assembly.GetTypes().Where(type => 
 (type.Namespace == typeof(ISomethingService).Namespace || type.Namespace == typeof(ISomethingService2).Namespace) && type.IsInterface);

foreach (var @class in classes)
{
    var methods = @class.GetMethods();

    foreach (var method in methods)
    {
        foreach (var genericType in method.ReturnType.GenericTypeArguments)
        {
            if (IsNullable(genericType))
            {
                Console.WriteLine($"Return type of method {@class.Name}.{method.Name} is nullable: {genericType.Name}");
            }
        }
    }
 }

可为空的判断目前是这样实现的，但不能按预期工作:

private static bool IsNullable<T>(T obj)
{
    if (obj == null) return true; // obvious
    Type type = typeof(T);
    if (!type.IsValueType) return true; // ref-type
    if (Nullable.GetUnderlyingType(type) != null) return true; // Nullable<T>
    return false; // value-type
}

有没有办法达到想要的结果(例如，如果在Task<T>之后的第一级(泛型)上设置了?，则只有IsNullable是true)？