title: ASP.NET Core MediatR error: Register your handlers with the container
body: <p>I have a .Net Core app where i use the <code>.AddMediatR</code> extension to register the assembly for my commands and handlers following a CQRS approach.</p>
  
  <p>In ConfigureServices in Startup.cs i have used the extension method from the official package <code>MediatR.Extensions.Microsoft.DependencyInjection</code> with the following parameter:</p>
  
  <pre><code>services.AddMediatR(typeof(AddEducationCommand).GetTypeInfo().Assembly);  
  </code></pre>
  
  <p>The command and commandhandler classes are as follow:</p>
  
  <p><strong>AddEducationCommand.cs</strong></p>
  
  <pre><code>public class AddEducationCommand : IRequest&lt;bool&gt;
  {
      [DataMember]
      public int UniversityId { get; set; }
  
      [DataMember]
      public int FacultyId { get; set; }
  
      [DataMember]
      public string Name { get; set; }
  }
  </code></pre>
  
  <p><strong>AddEducationCommandHandler.cs</strong></p>
  
  <pre><code>public class AddEducationCommandHandler : IRequestHandler&lt;AddEducationCommand, bool&gt;
      {
          private readonly IUniversityRepository _repository;
          public AddEducationCommandHandler(IUniversityRepository repository)
          {
              _repository = repository;
          }
  
          public async Task&lt;bool&gt; Handle(AddEducationCommand command, CancellationToken cancellationToken)
          {
              var university = await _repository.GetAsync(command.UniversityId);
  
              university.Faculties
                  .FirstOrDefault(f =&gt; f.Id == command.FacultyId)
                  .CreateEducation(command.Name);
  
              return await _repository.UnitOfWork.SaveEntitiesAsync();
          }
      }
  </code></pre>
  
  <p>When i run the REST endpoint that executes a simple <code>await _mediator.Send(command);</code> code, i get the following error from my log:</p>
  
  <pre><code>Error constructing handler for request of type MediatR.IRequestHandler`2[UniversityService.Application.Commands.AddEducationCommand,System.Boolean]. Register your handlers withthe container. See the samples in GitHub for examples.
  </code></pre>
  
  <p>I tried to look through the official examples from the docs without any luck. Does anyone know how i configure MediatR to work properly? Thanks in advance.</p>