WebAPI ActionFilter Await ExecuteActionFilterAsync No Result

Question

I try to create a filter to modify the content. For some reason the var result = await actionContext.Request.Content.ReadAsStringAsync(); does not wait and returns me empty values. I'm sure that there is data. Checked directly inside controller and header. Is there maybe a workaround. Can be blocking, too (HttpContent seems just to have async methods).

 public class AsyncAttribute : FilterAttribute, IActionFilter
{
    public async Task<HttpResponseMessage> ExecuteActionFilterAsync(HttpActionContext actionContext, CancellationToken cancellationToken,
        Func<Task<HttpResponseMessage>> continuation)
    {
        await InternalActionExecuting(actionContext, cancellationToken);

        if (actionContext.Response != null)
        {
            return actionContext.Response;
        }

        HttpActionExecutedContext executedContext;

        try
        {
            var response = await continuation();
            executedContext = new HttpActionExecutedContext(actionContext, null)
            {
                Response = response
            };
        }
        catch (Exception exception)
        {
            executedContext = new HttpActionExecutedContext(actionContext, exception);
        }

        await InternalActionExecuted(executedContext, cancellationToken);
        return executedContext.Response;
    }

    public virtual async Task InternalActionExecuting(HttpActionContext actionContext, CancellationToken cancellationToken)
    {
        //////////////////////////////////////////////////////////////////////////
        var result = await actionContext.Request.Content.ReadAsStringAsync();// <------------------------------------------------------
        //////////////////////////////////////////////////////////////////////////
    }

    public virtual async Task InternalActionExecuted(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken)
    {
    }
 }

I like to have a filter attribute for some content manipulation stuff. — MR.ABC, May 13 '14 at 05:21
"I have a thing that changes stuff". Thanks. Could you vague that up for me? — Aron, May 13 '14 at 05:22
@MR.ABC I believe a sample HTTP request would be nice, because I believe your issue has something to do with that. — Matías Fidemraizer, May 13 '14 at 05:24
@Matías Fidemraizer i need to go. I do that later. Using json content-type maybe somebody will try it before. — MR.ABC, May 13 '14 at 05:27
@MR.ABC We don't need to try that. Your code should work, do you really think that something like WebAPI would become popular if basic things aren't working? It's your code/environment what generates the issue... — Matías Fidemraizer, May 13 '14 at 05:34

score 0 · Answer 1 · edited May 23 '17 at 10:25

You should not be accessing the body in an action filter, if you have any thing else accessing the body in parameter binding it might be already gone.
Why are you calling actionExecuted inside the action executing overload? The pattern is one gets called before the action is run and one after.
For some reason it also looks like you are trying to implement the filter pipeline itself inside this method.

If you want to bind data from the body your recommended alternative is to use a formatter. Implement a MediaTypeFormatter and read what you need into a string. See one example

My wild bet here is that something else already read the body stream (and technically you are done at the point) and you can try and rewind it first (it will only work if you are in buffered mode).

WebAPI ActionFilter Await ExecuteActionFilterAsync No Result

1 Answers1