How to use the new IValueResolver of AutoMapper?

How to use the new IValueResolver of AutoMapper?

The IValueResolver interface of AutoMapper allows you to create a custom value resolver to resolve the value of a single destination member using the values of one or more source members. Here's an example of how to use IValueResolver:

  • Create a custom value resolver that implements the IValueResolver interface. In this example, we are creating a resolver to map a Person object to a PersonDto object:
public class PersonResolver : IValueResolver<Person, PersonDto, string> { public string Resolve(Person source, PersonDto destination, string destMember, ResolutionContext context) { return source.FirstName + " " + source.LastName; } }

In this example, we are concatenating the FirstName and LastName properties of the Person object and returning the result as a string.

  • Configure AutoMapper in the Startup.cs file by adding the following code to the ConfigureServices() method:
var mapperConfig = new MapperConfiguration(cfg => { cfg.CreateMap<Person, PersonDto>() .ForMember(dest => dest.FullName, opt => opt.MapFrom<PersonResolver>()); });

In this example, we are creating a mapping from Person to PersonDto and using the ForMember() method to specify that the FullName property of the PersonDto object should be mapped using the PersonResolver value resolver.

  • Use AutoMapper to map the Person object to the PersonDto object:
var person = new Person { FirstName = "John", LastName = "Doe" }; var mapper = mapperConfig.CreateMapper(); var personDto = mapper.Map<PersonDto>(person);

In this example, we are creating a Person object, creating an instance of the AutoMapper mapper using the CreateMapper() method, and using the mapper to map the Person object to a PersonDto object.

When the mapping occurs, AutoMapper will call the Resolve() method of the PersonResolver value resolver to get the value of the FullName property of the PersonDto object. The value resolver will use the FirstName and LastName properties of the Person object to generate the value and return it to AutoMapper, which will set the value of the FullName property of the PersonDto object to the generated value.

Examples

  1. "AutoMapper IValueResolver tutorial"

    • Description: Find a tutorial on using the new IValueResolver in AutoMapper for mapping complex types in C#.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, string> { public string Resolve(Source source, Destination destination, string destMember, ResolutionContext context) { // Custom logic to resolve the value return "ResolvedValue"; } }

  2. "AutoMapper IValueResolver example"

    • Description: Explore an example demonstrating the implementation of IValueResolver in AutoMapper for custom value resolution.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, string> { public string Resolve(Source source, Destination destination, string destMember, ResolutionContext context) { // Custom logic to resolve the value based on source return source.SomeProperty + "_Resolved"; } }

  3. "AutoMapper IValueResolver complex mapping"

    • Description: Learn how to use IValueResolver for complex mapping scenarios in AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, ComplexType> { public ComplexType Resolve(Source source, Destination destination, ComplexType destMember, ResolutionContext context) { // Custom logic to map properties of ComplexType return new ComplexType { PropertyA = source.A, PropertyB = source.B }; } }

  4. "AutoMapper IValueResolver nested mapping"

    • Description: Understand how to use IValueResolver for nested object mapping with AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, NestedType> { public NestedType Resolve(Source source, Destination destination, NestedType destMember, ResolutionContext context) { // Custom logic to map properties of NestedType return new NestedType { InnerProperty = source.Inner.A + "_Resolved" }; } }

  5. "AutoMapper IValueResolver dependency injection"

    • Description: Find information on how to use dependency injection with IValueResolver in AutoMapper.
    • Code:
      // Add this in your startup or configuration services.AddTransient<IValueResolver<Source, Destination, string>, MyResolver>();

  6. "AutoMapper IValueResolver conditional mapping"

    • Description: Learn how to implement conditional mapping using IValueResolver in AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, string> { public string Resolve(Source source, Destination destination, string destMember, ResolutionContext context) { // Conditional logic to resolve the value return source.Condition ? "ResolvedValue" : "FallbackValue"; } }

  7. "AutoMapper IValueResolver with async logic"

    • Description: Explore how to use IValueResolver with asynchronous logic for mapping in AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, Task<string>> { public async Task<string> Resolve(Source source, Destination destination, Task<string> destMember, ResolutionContext context) { // Asynchronous logic to resolve the value return await SomeAsyncMethod(); } }

  8. "AutoMapper IValueResolver source and destination context"

    • Description: Understand how to access source and destination context in IValueResolver during mapping with AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, string> { public string Resolve(Source source, Destination destination, string destMember, ResolutionContext context) { // Access source and destination context var sourceValue = context.SourceValue; var destinationValue = context.DestinationValue; return "ResolvedValue"; } }

  9. "AutoMapper IValueResolver multiple source properties"

    • Description: Learn how to use IValueResolver with multiple source properties in AutoMapper.
    • Code:
      public class MyResolver : IValueResolver<Source, Destination, string> { public string Resolve(Source source, Destination destination, string destMember, ResolutionContext context) { // Custom logic using multiple source properties return source.PropertyA + source.PropertyB; } }

  10. "AutoMapper IValueResolver generic mapping"

    • Description: Explore how to implement generic mapping with IValueResolver in AutoMapper.
    • Code:
      public class MyResolver<T> : IValueResolver<Source, Destination, T> { public T Resolve(Source source, Destination destination, T destMember, ResolutionContext context) { // Generic mapping logic return SomeGenericMapping<T>(source); } }

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