Merge .NET 4.0 Tasks / Extensions of Different Types

I am currently implementing System.Web.Http.IActionFilterthat calls an internal service to determine if the current request can continue. The problem I am facing is returning Task<T1>based on the piece of logic enclosed in Task<T2>.

An example may help.

The internal service API is implemented using Tasks. The logic is trivial using .NET 4.5 async / wait:

public async Task<HttpResponseMessage> ExecuteActionFilterAsync(HttpActionContext actionContext, CancellationToken cancellationToken, Func<Task<HttpResponseMessage>> continuation)
{
    UserAuthenticationResult authResult = await HitInternalServiceAsync();

    if (!authResult.IsAuthenticated)
    {
        throw new HttpResponseException("User is not authenticated", HttpStatusCode.Unauthorized);
    }

    return await continuation();
}

However, more complicated with the old task API in .NET 4.0 ;

public Task<HttpResponseMessage> ExecuteActionFilterAsync(HttpActionContext actionContext, CancellationToken cancellationToken, Func<Task<HttpResponseMessage>> continuation)
{
    return HitInternalServiceAsync()
            .ContinueWith(t1 => {
                UserAuthenticationResult authResult = t1.Result;

                if (!authResult.IsAuthenticated)
                {
                    throw new HttpResponseException("User is not authenticated", HttpStatusCode.Unauthorized);
                }

                //Hack hack - this blocks the thread until the task retuned by continuation() completes
                return continuation().Result;
            });
}

The difficult part arises when authentication is successful - I want to wait for the task returned by the continue function.

.NET 4.0 , , continuation(), , API continuation(), .

: .NET 4.0?

API , , .

: , 4.0 - ASP.NET, HttpContext.Current . ...

public Task<HttpResponseMessage> ExecuteActionFilterAsync(HttpActionContext actionContext, CancellationToken cancellationToken, Func<Task<HttpResponseMessage>> continuation)
{
    Task<UserAuthenticationResult> authResultTask = HitInternalServiceAsync();

    var authResult = authResultTask.Result;

    if (!authResult.IsAuthenticated)
    {
        throw new HttpResponseException("User is not authenticated", HttpStatusCode.Unauthorized);
    }

    return continuation();
}