Action Filters returns an empty body in asp.net-core 2.0

[jernejk]

I have same problem as #5594 and the potential fix doesn't work.
When Result is set, status code is changed (422) but response is empty.

I tried different combinations of setting up the actionExecutedContext.Exception and actionExecutedContext.ExceptionHandled.

Initial code:

public override void OnActionExecuted(ActionExecutedContext actionExecutedContext)
{
    if (actionExecutedContext.Exception is ModelValidationException validationException)
    {
        var result = new BadRequestObjectResult(validationException.Errors) { StatusCode = 422 };
        actionExecutedContext.Exception = null;
        actionExecutedContext.ExceptionHandled = true;
        actionExecutedContext.Result = result;
    }

    base.OnActionExecuted(actionExecutedContext);
}

As well as suggested workaround:

public override void OnActionExecuted(ActionExecutedContext actionExecutedContext)
{
    if (actionExecutedContext.Exception is ModelValidationException validationException)
    {
        actionExecutedContext.ExceptionHandled = false; // mark exception as handled
        actionExecutedContext.HttpContext.Response.Clear();
        actionExecutedContext.HttpContext.Response.StatusCode = 422;
        actionExecutedContext.HttpContext.Response.ContentType = new MediaTypeHeaderValue("application/json").ToString();
        string json = JsonConvert.SerializeObject(validationException.Errors);
        actionExecutedContext.HttpContext.Response.WriteAsync(json, Encoding.UTF8).Wait();
    }

    base.OnActionExecuted(actionExecutedContext);
}

It works as expected on OnActionExecuting:

public override void OnActionExecuting(ActionExecutingContext actionContext)
{
    if (!actionContext.ModelState.IsValid)
    {
        //422 - Unprocessable Entity
        var result = new BadRequestObjectResult(actionContext.ModelState) { StatusCode = 422 };
        actionContext.Result = result;
    }
}

Edit:
The ValidationException.Errors is Dictionary<string, IEnumerable<string>> so that JSON structure is consistent with actionContext.ModelState.

[rathorer]

I changed actionExecutedContext.ExceptionHandled = true; to
actionExecutedContext.ExceptionHandled = false;.
It worked for me.

[mkArtakMSFT]

@rynowak, @dougbu what is the expected behavior in the first sample @rathorer has shared?

[rynowak]

Wait, never mind, this is an action filter not an exception filter.

[rynowak]

It's expected that setting ActionExecutedContext.Result to a result value will replace the action result returned by the method and cause the new action result to run if the action is considered successful.
Setting:

actionExecutedContext.Exception = null;

OR

actionExecutedContext.ExceptionHandled = true;

Should mark the action as successful.

Do you have a repro project you can share for this?

[jernejk]

@rathorer solution worked!
It seems I haven't used actionExecutedContext.ExceptionHandled = false; for all of the combinations.

@rynowak I'll create a repro where having actionExecutedContext.ExceptionHandled = true; didn't work properly on the weekend.

Thanks for the help, we can now do proper validation for the forms. :)

[mkArtakMSFT]

@jernejk, have you got a chance to prepare a sample repro project so we can investigate it?

[mkArtakMSFT]

Hi. We're closing this issue as no response or updates have been provided in a timely manner and we have been unable to reproduce it. If you have more details and are encountering this issue please add a new reply and re-open the issue.