Is there only one instance of the JsonExceptionFilterAttribute?

“Collection was modified; enumeration operation may not execute.”

https://github.com/RicoSuter/NSwag/blob/master/src/NSwag.AspNet.WebApi/JsonExceptionFilterAttribute.cs#L108

Newtonsoft has seemed to have compatibility issues in other posts so here is my version of newtonsoft and dotnet:

• newtonsoft: 12.0.1
• Microsoft.AspNet.Core : 5.2.3

There seems to be a problem in the JsonExceptionFilterAttribute where when I use it to generate an exception message on the client side it is works, but generates the collection was modified error above.

Here is the console output: at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.List1.Enumerator.MoveNextRare() at System.Collections.Generic.List1.Enumerator.MoveNext() at NSwag.AspNet.WebApi.JsonExceptionFilterAttribute.CopySettings(JsonSerializerSettings settings) at NSwag.AspNet.WebApi.JsonExceptionFilterAttribute.OnActionExecuted(HttpActionExecutedContext context) at System.Web.Http.Filters.ActionFilterAttribute.OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken) — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext() — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext() — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext() — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() at DaksWeb.Security.AddChallengeOnUnauthorizedResult.<ExecuteAsync>d__9.MoveNext() in D:\daks\Source\Daks\DaksWeb\Security\AddChallengeOnUnauthorizedResult.cs:line 25 — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext() — End of stack trace from previous location where exception was thrown — at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()

[RicoSuter]

Created a PR which fixes this for me: https://github.com/RicoSuter/NSwag/pull/2292

[kwbonte]

@RicoSuter I believe the issue you have encountered is not running nuget restore, if you are using visual studio to run this, in the top right there is a search bar, type manage nuget packages, select the first option, there should be a list of packages and a popup option to restore. select restore and run the app. it should start on a 404 error and you have to manually change the url to the specified path above.