Default value for all string properties when source properties are null

Question

Is it possible to set all string properties that are null in my source object to some default value within my destination object using AutoMapper?

For example, let's say I had the following two class definitions:

public class UniversalForm
{
    public string LastName { get; set; }
    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string FaxNumber { get; set; }
    ...
}

public class UniversalFormDto
{
    public string LastName { get; set; }
    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string FaxNumber { get; set; }
    ...
}

Now, MiddleName and FaxNumber are properties that are likely to be null in the UniversalForm class. So what I would like to be able to do is if FaxNumber or MiddleName are null then in UniversalFormDto object I would like for the value of the corresponding properties to be set to "N/A".

I know this can be accomplished by creating a mapping for each individual member, but I would like to avoid that if at all possible.

I'm looking for a way to define a default value for all my string properties to be used when the corresponding property on my source object (UniversalForm) is null.

Aske B. · Accepted Answer · 2016-11-15 12:32:56Z

11

Here's a few methods I know:

ForAllMembers

All null values on all properties will be substituted as "N/A". Will crash if any of the properties can't be mapped to a string:

cfg.CreateMap<UniversalForm, UniversalFormDto>()
.ForAllMembers(opt => opt.NullSubstitute("N/A"));

ForMember

A substitute for every individual property:

cfg.CreateMap<UniversalForm, UniversalFormDto>()
.ForMember(dto => dto.FirstName, opt => opt.NullSubstitute("N/A"))
...
;

ConvertUsing

Universal substitute for all null strings in any property:

cfg.CreateMap<string, string>().ConvertUsing(s => s ?? "N/A");

answered Nov 15, 2016 at 12:32

Aske B.

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Comments

Sven Grosen · Accepted Answer · 2021-04-27 17:52:22Z

5

Not sure if these existed when the question was posted, but I'd suggest using a Value Transformer like this:

var configuration = new MapperConfiguration(cfg => {
    cfg.ValueTransformers.Add<string>(val => val ?? "N/A");
});

or if using profiles:

public class MyProfile : Profile
{
   public MyProfile()
   {
     ValueTransformers.Add<string>(val => val ?? "N/A");
   }
}

answered Apr 27, 2021 at 17:52

Sven Grosen

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Comments

Shar1er80 · Accepted Answer · 2015-08-05 22:47:47Z

2

I'm not too familiar with AutoMapper, but after doing some research you may want to try conditional mapping for each property.

Mapper.CreateMap<Source, Target>()
      .ForMember(dest => dest.MiddleName, 
                 opt => opt.MapFrom
                 (src => String.IsNullOrEmpty(src.MiddleName) 
                             ? "N/A" 
                             : src.MiddleName));

Hope this helps.

edited Aug 5, 2015 at 22:47

answered Aug 5, 2015 at 22:32

Shar1er80

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Comments

Brian · Accepted Answer · 2015-08-05 22:07:35Z

1

You can set your desired default properties in the constructor:

public UniversalFormDto() 
{
    FaxNumber = "N/A";
    MiddleName = "N/A";
    //etc...
}

answered Aug 5, 2015 at 22:07

Brian

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1 Comment

Rudy Padron Over a year ago

That's probably what I will do if it turns out that AutoMapper can't do what I need it to do.

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