C# AutoMapper 映射如果不为空，否则自定义转换
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AutoMapper Map If Not Null, Otherwise Custom Convert
提问by RPM1984
Here's my code:
这是我的代码：
Mapper.CreateMap<Foo, Foo2>()
.ForMember(dest => dest.Bar, opt => opt.MapFrom(src => src.Bar == null ? new BarViewModel() : src.Bar))
Basically, "BarViewModel" has a parameterless ctor which sets up properties in the class.
基本上，“BarViewModel”有一个无参数的构造函数，它在类中设置属性。
So i'm trying to say to AutoMapper:
所以我想对 AutoMapper 说：
If the value is null, then use the ctor for the class. otherwise use the mapping you have in place
如果值为空，则使用类的构造函数。否则使用您现有的映射
The above is giving me a C# compiler error. And i'm guessing a cast wouldn't work either.
上面给了我一个 C# 编译器错误。而且我猜演员也行不通。
So is there a AutoMapper trick to do this?
那么是否有 AutoMapper 技巧可以做到这一点？
Worst case i could remove that mapping for that property, and just do:
最坏的情况是，我可以删除该属性的映射，然后执行以下操作：
var mapped = Mapper.Map<Foo,Foo2>(src);
if (mapped.Bar == null) mapped.Bar = new BarViewModel();
But that's a tad ugly.
但这有点难看。
Ideas?
想法？
采纳答案by k0stya
You can use custom value resolver. The following should work:
您可以使用自定义值解析器。以下应该工作：
Mapper.CreateMap<Foo, Foo2>()
.ForMember(dest => dest.Bar, opt => opt.ResolveUsing(src => src.Bar == null ? new Bar() : Mapper.Map<Bar,Bar2>(src.Bar)))
回答by devuxer
I don't get a compiler error for the following:
我没有收到以下编译器错误：
public class Foo
{
public Bar Bar { get; set; }
}
public class Foo2
{
public Bar Bar { get; set; }
}
public class Bar
{
public int Id { get; set; }
public Bar()
{
Id = 3;
}
}
CreateMap<Foo, Foo2>()
.ForMember(
dest => dest.Bar,
opt => opt.MapFrom(src => src.Bar == null ? new Bar() : src.Bar));
...so I'm wondering if the problem is not actually with your mapping?
...所以我想知道问题是否实际上不在于您的映射？
回答by Vijai
Now you can use .NullSubstitute()to replace NULL value to some custom value in Automapper, e.g.:
现在您可以使用.NullSubstitute()Automapper 将 NULL 值替换为某些自定义值，例如：
CreateMap<SMModel, VM_SMModel>()
.ForMember(d => d.myDate, o => o.NullSubstitute(new DateTime(2017,12,12)));
回答by spottedmahn
As of Automapper 8, ResolveUsingis no longer an optionbut inline Func's, IValueResolverand IMemberValueResolverare .
从 Automapper 8 开始，ResolveUsing不再是一个选项，而是 inlineFunc的，IValueResolver并且IMemberValueResolver是 。
Inline Func Example
内联函数示例
Mapper.Initialize(cfg =>
{
cfg.CreateMap<Foo, FooViewModel>()
.ForMember(dest => dest.BarViewModel,
opt => opt.MapFrom((src, dest) =>
{
if (src.Bar == null)
return new BarViewModel ();
return Mapper.Map<Bar, BarViewModel>(src.Bar);
}));
cfg.CreateMap<Bar, BarViewModel>();
});
IMemberValueResolver Example
IMemberValueResolver 示例
Mapper.Initialize(cfg =>
{
cfg.CreateMap<Foo, FooViewModel>()
.ForMember(dest => dest.BarViewModel,
opt => opt.MapFrom<NullBarResolver, Bar>(src => src.Bar));
cfg.CreateMap<Bar, BarViewModel>();
});
public class NullBarResolver : IMemberValueResolver<object, object, Bar, BarViewModel>
{
public BarViewModel Resolve(object source, object destination, Bar sourceMember,
BarViewModel destMember, ResolutionContext context)
{
if (sourceMember == null)
return new BarViewModel();
return Mapper.Map(sourceMember, destMember);
}
}
There's some good documentation on Custom Value Resolvers here.
这里有一些关于自定义值解析器的很好的文档。
