One Notification Handler ?

[Val9000]

So currently I have this scenario, where each handler will have 1:1 the same logic, so if i have 10 notifications / events that will mean I will also have 10 handler methods...

Smth like this

public Task Handle(TestResultTestParameterAdded notification, CancellationToken cancellationToken)
    => HandleTestResultEvent(notification, cancellationToken);

public Task Handle(TestResultTestParameterRemoved notification, CancellationToken cancellationToken)
    => HandleTestResultEvent(notification, cancellationToken);

public Task Handle(TestResultTestParameterValueChanged notification, CancellationToken cancellationToken)
    => HandleTestResultEvent(notification, cancellationToken);

public Task Handle(TestResultTestRemoved notification, CancellationToken cancellationToken)
    => HandleTestResultEvent(notification, cancellationToken);

public Task Handle(TestResultUnlinkedFromRequirement notification, CancellationToken cancellationToken)
    => HandleTestResultEvent(notification, cancellationToken);

public Task Handle(TestResultCustomExpectedResultCommentChanged notification, CancellationToken cancellationToken) 
    => HandleTestResultEvent(notification, cancellationToken);

    public interface ITestResultContextSubscriber :
          INotificationHandler<TestResultRenamed>,
          INotificationHandler<TestResultTestCreated>,
          INotificationHandler<TestResultTestCommentChanged>,
          INotificationHandler<TestResultTestConceptChanged>,
          INotificationHandler<TestResultTestParameterAdded>,
          INotificationHandler<TestResultTestParameterRemoved>,
          INotificationHandler<TestResultTestParameterValueChanged>,
          INotificationHandler<TestResultTestRemoved>,
          INotificationHandler<TestResultUnlinkedFromRequirement>
          {
          }

Is it possible to just have one Handler, and maybe 1 event that has it's own unqiue handler ??

TestResultRenamed and all the other events listed inherit from TestResultEvent, which, in turn, inherits from DomainEvent, and DomainEvent implements INotification from MediatR.

I have tried the follwing but the handle never gets called.

services.AddScoped<ITestResultContextSubscriber<TestResultEvent>, TestResultContextSubscriber>();

public interface ITestResultContextSubscriber<in T> :
    INotificationHandler<T> where T : TestResultEvent
{
}

public class TestResultContextSubscriber : ITestResultContextSubscriber<TestResultEvent>{
     
      public Task Handle(TestResultEvent notification, CancellationToken cancellationToken) =>
           HandleTestResultEvent(notification, cancellationToken);
}

Thanks in advance !

[zachpainter77]

I think you should be able to do this.. I tried to make this example as close as I could to yours.

//some type of type constraint.. I used interface.
 public interface ITestResultEvent 
 {
     bool HandlerCalled { get; set; }
 }

//event class implements the constraint above and also INotification for MediatR
 public class TestResultTestParameterAdded : ITestResultEvent, INotification
 {
     public bool HandlerCalled { get; set; }
 }

//second event class like above to test that multiple events can have the same notification handler
 public class TestResultTestParameterRemoved : ITestResultEvent, INotification
 {
     public bool HandlerCalled { get; set; }
 } 

//generic notification handler handles all event notifications that implement ITestResultEvent from above
 public class TestResultEventNotificationHandler<TNotification> : INotificationHandler<TNotification>
     where TNotification : class, ITestResultEvent, INotification
 {
     public Task Handle(TNotification notification, CancellationToken cancellationToken)
     {
         notification.HandlerCalled = true;
         return Task.CompletedTask;
     }
 }
 

Then I made a test to test if each notification was calling the same handler.

[Fact]
public async Task Test()
{
    var mediator = _provider.GetService<IMediator>();

    var addedNotification = new TestResultTestParameterAdded();
    var removedNotification = new TestResultTestParameterRemoved();

    await mediator!.Publish(addedNotification);
    await mediator!.Publish(removedNotification);

    addedNotification.HandlerCalled.ShouldBeTrue();     //true
    removedNotification.HandlerCalled.ShouldBeTrue(); //true
}