Question about registering a behavior

[bancroftway]

Discussed in #1074

^{Originally posted by bancroftway September 26, 2024}
I have a question regarding correct way to register my behavior whose complete code is below.

I have tried this way, but the behavior does not get called:

 builder.Services.AddMediatR(cfg => {
     cfg.RegisterServicesFromAssemblies(typeof(Program).Assembly);
     cfg.AddBehavior<IPipelineBehavior<IAppRequest<BaseResponse>,BaseResponse>, UnhandledExceptionBehavior<IAppRequest<BaseResponse>, BaseResponse>>();
 });

public class UnhandledExceptionBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IAppRequest<TResponse>
    where TResponse : BaseResponse
{
    private readonly ILogger<UnhandledExceptionBehavior<TRequest, TResponse>> _logger;

    public UnhandledExceptionBehavior(ILogger<UnhandledExceptionBehavior<TRequest, TResponse>> logger)
    {
        _logger = logger;
    }

    public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
    {
        try
        {
            return await next();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Unhandled Exception for Request {Name} {@Request}", typeof(TRequest).Name, request);

            var response = Activator.CreateInstance<TResponse>();
            response.IsSuccess = false;
            response.ErrorMessage = $"An error occurred while processing your request: {ex.Message}";

            return response;
        }
    }

[balogun14]

try separating MediatR configuration from the behavior registration. like this
builder.Services.AddMediatR(cfg =>
{
cfg.RegisterServicesFromAssemblies(typeof(Program).Assembly);
});

builder.Services.AddTransient(typeof(IPipelineBehavior<,>), typeof(UnhandledExceptionBehavior<,>));

[duongphuhiep]

try separating MediatR configuration from the behavior registration. like this builder.Services.AddMediatR(cfg => { cfg.RegisterServicesFromAssemblies(typeof(Program).Assembly); });

builder.Services.AddTransient(typeof(IPipelineBehavior<,>), typeof(UnhandledExceptionBehavior<,>));

I won't work, I had the same problem

[duongphuhiep]

In order to register Generic behaviors you have to use AddOpenBehavior instead of AddBehavior for eg: cfg.AddOpenBehavior(typeof(UnhandledExceptionBehavior<,>))

[1124541815]

泛型他没有提供注入，使用atuofac
builder.Host.UseServiceProviderFactory(new AutofacServiceProviderFactory());
builder.Host.ConfigureContainer(builder =>
{
builder.RegisterSource(new ContravariantRegistrationSource());
builder.RegisterGeneric(typeof(UnhandledExceptionBehavior<,>)).AsImplementedInterfaces();
}); 看下是否可以

[tolgacakir]

can you share your request? you should inherit from IAppRequest and your response should be BaseResponse.

[bancroftway]

Here is my request and response. Please help me with the registration code for the behavior as I am unable to understand the correct code to register the behavior, as this is not an open behavior

public sealed record GetTopQuestionsQry : IRequest<GetTopQuestionsQryResult>;

public sealed record GetTopQuestionsQryResult : BaseResponse
{
    public List<QuestionDto> Questions { get; set; }
}

[tolgacakir]

There are 2 ways to solve this issue:

1 - Use IRequest instead of IAppRequest in your behavior:

public class UnhandledExceptionBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : **IRequest<TResponse>**
    where TResponse : BaseResponse
{
    //...
}

2 - If you want to use IAppRequest, first you must define like this:

public interface IAppRequest<T> : IRequest<T>
{
}

and define your request like this:

public sealed record GetTopQuestionsQry : IAppRequest<GetTopQuestionsQryResult>;

[github-actions]

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