Automapper: Hydrate int? based on conditions

Question

I have the following code:

[Test] public void ConditionalMapping() { var src = new Sample1 {Age = 1, Number = null}; var dest = new Sample2 {Age = null, Number = 1}; Hydrate(src, dest, false); Assert.That(dest.Age, Is.EqualTo(1)); Assert.That(dest.Number, Is.EqualTo(1)); src = new Sample1 {Age = null, Number = 1}; dest = new Sample2 {Age = 1, Number = null}; Hydrate(src, dest, true); Assert.That(dest.Age, Is.Null); Assert.That(dest.Number, Is.EqualTo(1)); } public void Hydrate(Sample1 src, Sample2 dest, bool allowOverride) { if (!dest.Age.HasValue || allowOverride) dest.Age = src.Age; if (!dest.Number.HasValue || allowOverride) dest.Number = src.Number; } public class Sample1 { public int? Age { get; set; } public int? Number { get; set; } } public class Sample2 { public int? Age { get; set; } public int? Number { get; set; } } 

What basically moisturizes int? if the value is null , if allowOverride = true in which it will hydrate the value without checking the field value.

How do I do this in Automapper?

I know you can use .Condition () as shown here:

Automapper condition ignored

But I could not understand how:

• Apply int? based logic int? without defining it one by one.
• Enable allowOverride boolean in Mapper.

Answer 1

Perhaps I found a potential solution for you - depending on how you want to use the allowOverride flag.

If you want the flag to work the same for all mappings, you can create a TypeConverter as follows

 public class NullableIntConverter : ITypeConverter<int?, int?> { private bool AllowOverrides { get; set;} public NullableIntConverter(bool allowOverrides) { AllowOverrides = allowOverrides; } public int? Convert(ResolutionContext context) { var source = context.SourceValue as int?; var destination = context.DestinationValue as int?; if (destination.HasValue && !AllowOverrides) return destination; else return source; } } 

Initialize it as follows:

 Mapper.CreateMap<Sample1, Sample2>(); Mapper.CreateMap<int?, int?>().ConvertUsing(new NullableIntConverter(true)); Mapper.AssertConfigurationIsValid(); 

Now it checks the assignment for the value and redefines it depending on your constructor argument.

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OR

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If you want to configure it for each mapping, then you can use ValueResolver (note that this code can do with some additional verification):

 public class NullableIntResolver : IValueResolver { public bool AllowOverrides { get; set; } public NullableIntResolver(bool allowOverrides) { AllowOverrides = allowOverrides; } public ResolutionResult Resolve(ResolutionResult source) { // Add validation for source and destination types return source.New( ResolveCore((int?) source.Value, DestinationMemberValue(source.Context)), typeof(int?)); } public int? ResolveCore(int? source, int? destination) { if (destination.HasValue && !AllowOverrides) return destination; else return source; } private int? DestinationMemberValue(ResolutionContext context) { var destObject = context.DestinationValue; var destMemberName = context.MemberName; return (int?) destObject .GetType() .GetProperty(destMemberName) .GetValue(destObject, null); } } 

Then you can initialize your mappings as follows:

 var allowOverrides = true; Mapper.CreateMap<Sample1, Sample2>() .ForMember(dest => dest.Age, opt => opt.ResolveUsing<NullableIntResolver>() .FromMember(src => src.Age) .ConstructedBy(() => new NullableIntResolver(allowOverrides))) .ForMember(dest => dest.Number, opt => opt.ResolveUsing<NullableIntResolver>() .FromMember(src => src.Number) .ConstructedBy(() => new NullableIntResolver(allowOverrides))); Mapper.AssertConfigurationIsValid();