将struct变量初始化为Nullable <int>

_yer必须声明为int？或Nullable .

    int? _yer;
    int _ner;

    public MyStruct(int? ver, int ner) {

        _yer = ver;
        _ner = ner;
    }
}

或者像这样:

    Nullable _yer;
    int _ner;

    public MyStruct(Nullable ver, int ner) {

        _yer = ver;
        _ner = ner;
    }
}

请记住,结构不能包含显式无参数构造函数.

error CS0568: Structs cannot contain explicit parameterless constructors