我应该如何处理关于C#8.0中的nullable选项的泛型问题？

c#

最近我有，如果通用类型是一个类或结构，详细之间的麻烦，当我宣布T有既不限制class也不是struct，也是#nullable选项启用，则泛型类型得到一些意外行为。例如，如果我用该类型构造一个成员T?并T指定为不可为空的结构类型，则该T?类型不会作为可空结构进行操作。这是一个关于它的解释代码：

public class MyClass<T> {
    ...
    public MyClass (T value, T? another) { ... }

    public void DoExample () {
        MyClass<int> a = new MyClass<int>(1, null); /* causes the CS1503 error, indicating int cannot receive null.
        In other words, T? is still int, not the nullable int.*/
    }
}

我应该怎么做才能解决这个问题？

也许解决了

最后，我找到了一个不完整但非常合理的解决方案来解决它。以下内容将帮助我们解决问题。

public class NullableWrapper<T> where T : notnull /* this constraint is not necessary
but if you want every type that specifies T to be non-nullable
and/or would not like to consider the null reference exception which may arise at Equals,
GetHashCode, and ToString, that would modify the type accuracy and/or your need. */ {
    public T Value { get; set; } = default!;

    internal NullableWrapper (T value) => this.Value = value;

    public override bool Equals (object? obj) => this.Value.Equals(obj);
    public override int GetHashCode () => this.Value.GetHashCode();
    public override string? ToString () => $"NullableWrapper({this.Value})";

    public static implicit operator NullableWrapper<T> (T itself)
        => new NullableWrapper<T>(itself);
    public static implicit operator T (NullableWrapper<T> itself)
        => itself.Value;
}

然后，我之前的代码更改为如下所示：

public class MyClass<T> where T : notnull {
    ...
    public MyClass (T value, NullableWrapper<T>? another) { ... }

    public void DoExample () {
        MyClass<int> a = new MyClass<int>(1, null); // this causes none of error.
        MyClass<string> b = new MyClass<string>("hello", null); // similarly, no error happens.
        MyClass<double> c = new MyClass<double>(2.6, 5.2); // it's equivalent to the previous.
        MyClass<string> d = new MyClass<string>("asd", "def"); // as well.
    }
}

回答