Unable to resolve service for type ‘automapper.imapper’ while attempting to activate

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Unable to resolve service for type ‘AutoMapper.IMapper’ while attempting to activate

When you see the error message “Unable to resolve service for type ‘AutoMapper.IMapper’ while attempting to activate”, it means that your application is trying to use AutoMapper but it can’t find the necessary dependencies.

AutoMapper is a library that simplifies object-to-object mapping. It allows you to define how to map properties from one object to another without writing repetitive code. To use AutoMapper in your application, you need to follow these steps:

  1. Install the AutoMapper NuGet package: Open the NuGet Package Manager in Visual Studio and search for “AutoMapper”. Install the latest version of the package.
  2. Create a mapping configuration: In your application startup file (for example, Startup.cs in ASP.NET Core), add a method to configure your mappings. This method usually has the name “ConfigureAutoMapper” or similar. Inside this method, you need to create a MapperConfiguration object and define your mappings. Here’s an example:
public void ConfigureAutoMapper()
{
    var config = new MapperConfiguration(cfg =>
    {
        cfg.CreateMap<SourceClass, DestinationClass>();
    });

    IMapper mapper = config.CreateMapper();
}
  1. Register the IMapper service: In the same startup file, you need to add the following line of code inside the ConfigureServices method:
services.AddSingleton<IMapper>(mapper);

By adding the IMapper service as a singleton, it will be available throughout your application whenever needed.

Make sure you also have the necessary using statements at the top of your startup file:

using AutoMapper;

Now, when you run your application, AutoMapper and its dependencies should be properly resolved. You should no longer see the “Unable to resolve service for type ‘AutoMapper.IMapper'” error.

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