Returning a RedirectResult with a URL causes NullReferenceException

[rob-hendrickx]

Investigative information

Please provide the following:

• Function App version (1.0 or 2.0): 2.0

Repro steps

1. Create a function app with a HTTP triggered function that returns a RedirectResult.
2. Run it on runtime version 2.0.12275.0

Expected behavior

Receive an HTTP redirect.
(it still works like this on version 2.0.12246.0)

Actual behavior

Receive an HTTP InternalServerError caused by a NullReferenceException in the UrlHelperBase.
(issue on 2.0.12275.0)

Known workarounds

Return a custom ActionResult like this:

public class CustomRedirectResult : StatusCodeResult
    {
        public string Url { get; set; }

        public CustomRedirectResult(string url) : base(307)
        {
            Url = url;
        }

        public override void ExecuteResult(ActionContext context)
        {
            base.ExecuteResult(context);
            context.HttpContext.Response.Redirect(Url, false);
        }
    }

Related information

Exception details:

System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=Microsoft.AspNetCore.Mvc.Core
StackTrace:
at Microsoft.AspNetCore.Mvc.Routing.UrlHelperBase..ctor(ActionContext actionContext) in //src/Microsoft.AspNetCore.Mvc.Core/Routing/UrlHelperBase.cs:line 31
at Microsoft.AspNetCore.Mvc.Routing.UrlHelperFactory.GetUrlHelper(ActionContext context) in //src/Microsoft.AspNetCore.Mvc.Core/Routing/UrlHelperFactory.cs:line 64
at Microsoft.AspNetCore.Mvc.Infrastructure.RedirectResultExecutor.ExecuteAsync(ActionContext context, RedirectResult result) in //src/Microsoft.AspNetCore.Mvc.Core/Infrastructure/RedirectResultExecutor.cs:line 48
at Microsoft.AspNetCore.Mvc.RedirectResult.ExecuteResultAsync(ActionContext context) in //src/Microsoft.AspNetCore.Mvc.Core/RedirectResult.cs:line 110
at Microsoft.Azure.WebJobs.Script.WebHost.Middleware.FunctionInvocationMiddleware.d__2.MoveNext() in C:\azure-webjobs-sdk-script\src\WebJobs.Script.WebHost\Middleware\FunctionInvocationMiddleware.cs:line 70
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() in E:\A_work\243\s\src\mscorlib\src\System\Runtime\ExceptionServices\ExceptionDispatchInfo.cs:line 132

[jsmith50-sc]

Getting the same here as well after the 2.16 update possibly.

[trydis]

We have a similar issue when returning a RedirectResult with a string, ends up with an internal server error. It works when pinning to 2.0.12246.0.

[tjgalama]

yep, also are running into this problem.

[tjgalama]

it looks like Type UrlHelperBase in Microsoft.AspNetCore.Mvc.Core,
Version=2.2.0.0 (previous runtime used 2.1.0.0) requires the ActionContext.RouteData to be set.
Since this property is null the NullReferenceException occurs.

This ActionContext instance is passed within the call-stack, but is created within method:
Microsoft.Azure.WebJobs.Script.WebHost.Middleware.FunctionInvocationMiddleware.Invoke(HttpContext context) within Microsoft.Azure.WebJobs.Script.WebHost.dll (File V. 2.0.12265.0). In this method the property RouteData is clearly not set.

For me adjusting the Function Runtime version is disturbing for our CI process.
Therefore, I added the following quick fix within my RedirectResult derived type;

public override Task ExecuteResultAsync(ActionContext context)
{
   ....
   if (context.RouteData == null)
      context.RouteData = new RouteData();
   return base.ExecuteResultAsync(context);
}

[rob-hendrickx]

@tjgalama Indeed, we noticed that that was the origin of the exception aswell. We created a workaround by creating a derived type of StatusCodeResult and generating a Redirect there. But your workaround is cleaner IMO. Well it works, so we'll leave it as is.

[rob-hendrickx]

Closed by accident

[brettsam]

@mathewc / @fabiocav -- could one of you look at this? Seems to be hitting a few people. @tjgalama's investigation above indicates it's a breaking change in ASP.NET 2.2. Is there any way we can work around this?

[pakrym]

cc @pranavkm