AutoMapper:如果source == null，则创建目标类型的实例 [英] AutoMapper: create instance of destination type if source == null

问题描述

如果源对象为null，是否可以将AutoMapper配置为返回目标类型的新实例?

Is it possible to configure AutoMapper to return a new instance of the destination type if the source object is null?

Source source = null;
Dest d1 = AutoMapper.Mapper.Map<Source, Dest>(source);
// d1 == null

// I'm looking for a way to configure AutoMapper to
// eliminate this code:
Dest d2 = AutoMapper.Mapper.Map<Source, Dest>(source) ?? new Dest();

推荐答案

(部分地)回答我自己的问题:

Answering my own question (partially):

AutoMapper具有名为AllowNullDestinationValues的配置属性，默认情况下将其设置为true.通过将此设置为false，我可以看到问题中显示的行为，例如:

AutoMapper has a configuration property named AllowNullDestinationValues which is set to true by default. By setting this to false, I get the behavior shown in the question, e.g:

Mapper.Configuration.AllowNullDestinationValues = false;

//...

Source source = null;
Dest d = AutoMapper.Mapper.Map<Source, Dest>(source);
// d is now a new instance of Dest

此解决方案适用于简单类型，其中源类型和目标类型映射良好.对于复杂的映射，我仍然有一些问题(我将更新问题以显示示例).

This solution works OK for simple types, where source and destination types map well. I still have some issues with complex mappings (I will update the question to show an example).

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