Question

让我们说，我们有两种用于映射的源类型和一个目标：

class TSource
{
    public float A { get; set; }
    public float B { get; set; }
}

class TSupport
{
    public float C { get; set; }
    public float D { get; set; }
}

class TDestination
{
    public float A { get; set; }
    public float B { get; set; }
    public float C { get; set; }
    public float D { get; set; }
}

使用TSource实例，使用某种方法获得TSupport的实例：

private TSupport GetSupportInstance(TSource source)

所以，通常，我会用双重映射来做到这一点：

Mapper.CreateMap<TSource, TDestination>();
Mapper.CreateMap<TSupport, TDestination>();
//...
var support = GetSupportInstance(source);

var destination = Mapper.Map<TSource, TDestination>(source);
Mapper.Map(support, destination);

这也可以使用手动解决方案在单一映射中完成：

Mapper.CreateMap<TSource, TDestination>()
    .ForMember(desc => desc.C, opt => opt.ResolveUsing(src =>
    {
        var support = GetSupportInstance(src);
        return support.C;
    }))
    .ForMember(desc => desc.D, opt => opt.ResolveUsing(src =>
    {
        var support = GetSupportInstance(src);
        return support.D;
    }));

正如您所看到的，我为每个属性使用了两次GetSupportInstance。所以，最后，我的问题是 - 是否有可能在映射中获得支持，以某种方式存储它，并在不同属性的映射中重用它？

Answer 1

这个怎么样：

Mapper.CreateMap<TSource, TDestination>()
    .ForMember(d => d.C, x => x.Ignore())
    .ForMember(d => d.D, x => x.Ignore())
    .AfterMap((src, dst) => {
        var support = GetSupportInstance(src);
        dst.C = support.C;
        dst.D = support.D;
    });

Answer 2

我可能会使用一个自定义解析器来缓存你需要的实例。它看起来像这样。

public class MySupportInstanceResolver : ValueResolver<TSource, TDestination> 
{
    private static readonly ISupportInstance _supportInstance;

    [ImportingConstructor]
    public MySupportInstanceResolver ()
    {
      _supportInstance=GetSupportInstance();
    }

    protected override string ResolveCore(Journal source)
    {
        return _supportInstance;
    }
}

然后你可以用它作为：

 cfg.CreateMap<TSource, Tdest>()
        .ForMember(dest => dest.C, 
            opt => opt.ResolveUsing<MySupportInstanceResolver>().FromMember(name => name.C));
});

＆＃34;存储＆＃34;使用automapper进行映射时的对象

2 个答案: