c# - 定义子类型映射时，新版本的 Automapper 抛出转换异常

Question

假设我有一个源类和两个目标类，一个更通用，一个更具体(继承自更通用的类):

public class Source
{   
    public int A { get; set; }
    public string Str { get; set; }
}

public class DestinationBase
{
    public int A { get; set; }
}

public class DestinationDerived : DestinationBase       
{
    public string Str { get; set; }
}

对于 Automapper 3.*，此代码完美运行:

    Mapper.Initialize(cfg => {
        cfg.CreateMap<Source, DestinationBase>();
        cfg.CreateMap<Source, DestinationDerived>()
            .IncludeBase<Source, DestinationBase>();
    });

    var src = new Source() { A = 1, Str = "foo" };
    var dest = new DestinationBase();

    Mapper.Map(src, dest);

但是升级到4.0.4后，这个映射抛出异常:

System.InvalidCastException: Unable to cast object of type 'DestinationBase' to type 'DestinationDerived'

我做错了什么或者这是 AutoMapper 中的错误？

.net fiddle中的代码:

• 3.3.1 版本:https://dotnetfiddle.net/6K9PtK
• 4.0.4 版本:https://dotnetfiddle.net/0mF8y8

Answer 1

看起来在 4.x 中您不再需要显式包含 base。以下工作正常并按预期将 a 输出为 1。

Mapper.Initialize(cfg => {
    cfg.CreateMap<Source, DestinationBase>();
    cfg.CreateMap<Source, DestinationDerived>();
});

var src = new Source() { a = 1, str = "foo" };
var dest = new DestinationBase();

Mapper.Map(src, dest);

Console.WriteLine("dest.a: " + dest.a);

同样，映射到 DestinationDerived 也可以正确映射从 base 继承的属性:

var src = new Source() { a = 1, str = "foo" };
var dest = new DestinationDerived();

Mapper.Map(src, dest);

Console.WriteLine("dest.a: " + dest.a);