AutoMapper使用错误的构造函数 [英] AutoMapper using the wrong constructor

问题描述

今天，我使用AutoMapper v1.1将功能全面的应用程序升级为现在使用AutoMapper v2.1，并且遇到了一些以前版本中从未遇到过的问题.

Today I upgraded a fully functioning application using AutoMapper v1.1 to now use AutoMapper v2.1 and I am coming across some issues that I never encountered using the previous version.

这是我的代码从 Dto 映射到 Domain 对象

Here is an example of my code mapping back from Dto to Domain object

public class TypeOne
{
   public TypeOne()
   {
   }

   public TypeOne(TypeTwo two)
   {
      //throw ex if two is null
   }

   public TypeOne(TypeTwo two, TypeThree three)
   {
      //throw ex if two or three are null
   }

   public TypeTwo Two {get; private set;}

   public TypeThree Three {get; private set;}
}

public class TypeOneDto
{
   public TypeOneDto()
   {
   }

   public TypeTwoDto Two {get; set;}

   public TypeThreeDto Three {get; set;}
}

...

Mapper.CreateMap<TypeThreeDto, TypeThree>();
Mapper.CreateMap<TypeTwoDto, TypeTwo>();
Mapper.CreateMap<TypeOneDto, TypeOne>();

var typeOne = Mapper.Map<TypeOne>(typeOneDto);

但是，我在v2.1上遇到的第一个问题是，当其中一个args为null且应使用1个arg构造函数时，AutoMapper试图使用具有2个args的构造函数.

However the first problem I encountered with v2.1 was that AutoMapper was trying to use the constructor with 2 args when one of the args was null and should be using the 1 arg constructor.

然后我尝试使用

Mapper.CreateMap<TypeOneDto, TypeOne>().ConstructUsing(x => new TypeOne());

但是我一直遇到无法解决的模棱两可的调用"错误.

But I kept getting an 'Ambiguous Invocation' error that I couldn't resolve.

然后我尝试

Mapper.CreateMap<TypeOneDto, TypeOne>().ConvertUsing(x => new TypeOne());

并确实使用无参数构造函数成功创建TypeOne对象，但随后却无法设置私有setter属性.

and that did successfully create the TypeOne object using the parameterless constructor but then it failed to set the private setter properties.

我已经在AutoMapper网站上寻求帮助，并下载了源代码以使外观看起来不错，但由于篇幅很小的文档并不能理解，而且ConstructUsing的单元测试也不多.

I have looked for help on the AutoMapper website and downloaded the source code to have a good look but didn't get far with the little documentation about and there were not many unit tests for ConstructUsing.

我是否明显缺少我应该使用v2.1进行更改的问题?与v1.1相比，它发生了如此大的变化，我感到很惊讶.

Is there anything obvious I am missing that I should change with v2.1? I am surprised that it has changed so much from v1.1.

推荐答案

您只需要添加这是代码:

Mapper.CreateMap<TypeOneDto, TypeOne>().ConstructUsing(
            (Func<ResolutionContext, TypeOne>) (r => new TypeOne()));

AutoMapper的当前版本如下所述:

Current version of AutoMapper works as described below:

1. 按参数计数对目标类型的构造函数进行排序

1. Sorts destination type constructors by parameter count

destTypeInfo.GetConstructors().OrderByDescending(ci => ci.GetParameters().Length);

采用第一个构造函数，该构造函数的参数与源属性匹配(不检查空值).在您的情况下，它是带有两个参数的构造函数.

Takes first constructor which parameters match source properties (without any check for null value). In your case it is constructor with two parameters.

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