【问题标题】：Making the C# compiler aware that a null-oblivious method may return null?Making the C# compiler aware that a null-oblivious method may return null?
【发布时间】：2022-12-02 05:52:06
【问题描述】：
AutoMapper's T IMapper.Map<T>(object) is null-oblivious for historical reasons. If you pass null, the result is null. The C# compiler does not warn about the possible null return when returning the result of Map from a method declared to return T.
Is there a way to make the compiler treat Map as if it had been declared as T? IMapper.Map<T>(object?)? I thought about wrapping IMapper in a different interface and injecting that instead, but that seems a bit heavy-handed.
【问题讨论】：
标签：
c#
automapper
nullability
【解决方案1】：
Firstly, object? is incorrect, as object is reference type and can accept null. Secondly, if generic parameter T is reference type, all good. And if it's value type — why don't you specify, for example, IMapper.Map<int?> instead of IMapper.Map<int>?
If for some reason you can't do that, you can cast a value type to its nullable twin:
object obj;
IMapper mapper;
// Initialize obj and mapper
var result = (int?)mapper.Map<int>(obj);