Method to handle exceptions in a async block to cannot convert return object to to async method return type

Question

I have implemented a method to handle exceptions around a async block like below:

public async Task<ServiceResponse<T>> RetryTest<T>(Func<Task<ServiceResponse<T>>> method)
    {
        try
        {
            return await method.Invoke();
        }
        catch (Exception exception)
        {
            return FormatExceptionResponse<T>(exception);
        }
    }

And use it to wrap async code like:

public async Task<ServiceResponse<DataJob>> Insert(DataJob entity)
    {

        return await RetryTest<ServiceResponse<DataJob>>(async () =>
        {
            Context.AddObject("DataJobs", entity);
            DataServiceResponse responses = await Context.SaveChangesAsync();

            return new ServiceResponse<DataJob>((HttpStatusCode)responses.Last().StatusCode, entity);

        });

    }

However the last return statement has an error: Cannot convert expression type ServiceResponse to async method return type ServiceResponse.

Any clue how to fix this?

Answer 1

Your definition of RetryTest accepts a T and then returns a ServiceResponse<T>

When you call it you've supplied: ServiceResponse<DataJob> as T , so the return type of RetryTest , since it needs to wrap T in a ServiceResponse , should return a ServiceResponse<ServiceResponse<DataJob>> rather than a ServiceResponse<DataJob> . (You're not returning that, hence the error.)

You simply want to pass DataJob as the generic argument to RetryTest instead of ServiceResponse<DataJob> .

Or, better yet, just remove the generic arguments entirely when calling RetryTest and let them be inferred properly, and then you can't mess it up.