[英]AutoMapper: Working with empty images (map to null in byte[] but not other collections)
In AutoMapper, the general concept for collections is that they should never be null.在 AutoMapper 中,collections 的一般概念是它们永远不应该是 null。 This makes sense, but how do I manage this when working with things like images?
这是有道理的,但是在处理图像之类的东西时,我该如何管理呢? Images, kept in C# as
byte[]
, must not be an empty array when it should be null
.图像,作为
byte[]
保存在 C# 中,当它应该是null
时不能是空数组。 I do not want to use something like the AllowNullCollections
configuration setting to change the default behaviour for all collections.我不想使用类似
AllowNullCollections
配置设置来更改所有 collections 的默认行为。 I only want byte[]
to map null
to null
.我只想要
byte[]
到 map null
到null
。
I'm currently using AutoMapper 8.我目前正在使用 AutoMapper 8。
The entities实体
public class SourceClass
{
public int Id { get; set; }
public byte[] Image1 { get; set; }
public byte[] Image2 { get; set; }
public byte[] Image3 { get; set; }
public List<SourceChildClass> Children { get; set; }
}
public class SourceChildClass
{
public string Test { get; set; }
}
public class DestinationClass
{
public int Id { get; set; }
public byte[] Image1 { get; set; }
public byte[] Image2 { get; set; }
public byte[] Image3 { get; set; }
public List<DestinationChildClass> Children { get; set; }
}
public class DestinationChildClass
{
public string Test { get; set; }
}
The mapping映射
CreateMap<SourceClass, DestinationClass>()
// .ForMember(dest => dest.Image1, ... default behaviour ...)
.ForMember(dest => dest.Image2, opts => opts.AllowNull()) // does not work
.ForMember(dest => dest.Image3, opts => opts.NullSubstitute(null)); // does not work
CreateMap<SourceChildClass, DestinationChildClass>();
The test code测试代码
var sourceEmpty = new SourceClass
{
Id = 1,
};
// I want the byte[] images to map to null,
// but "Children" should map to an empty list, as per the default behavour.
var destinationEmpty = Mapper.Map<SourceClass, DestinationClass>(sourceEmpty);
Have you tried value transformers?你试过价值转换器吗? You can apply this to a member.
您可以将此应用于成员。 https://docs.automapper.org/en/stable/Value-transformers.html
https://docs.automapper.org/en/stable/Value-transformers.html
I currently have two answers to this question.我目前对这个问题有两个答案。
On a case-by-case basis, using After Map .根据具体情况,使用After Map 。
CreateMap<SourceClass, DestinationClass>().AfterMap((src, dest) => { if (src.Image == null) dest.Image = null; });
On a more global scale, using a value transformer .在更全球范围内, 使用价值转换器。
cfg.ValueTransformers.Add<byte[]>(val => val.Length == 0? null: val);
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