An item with the same key has already been added

[andrewzamer]

I'm not sure what changed, but there seems to be a key duplicating causing this error. Is there a way to determine what the key is that's duplicating and where it's coming from?

500 : {"message":"An error has occurred.","exceptionMessage":"An item with the same key has already been added.","exceptionType":"System.ArgumentException","stackTrace":" at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)\r\n at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add)\r\n at Swashbuckle.Swagger.SchemaRegistry.GetOrRegister(Type type)\r\n at Swashbuckle.Swagger.SwaggerGenerator.CreateOperation(ApiDescription apiDescription, SchemaRegistry schemaRegistry)\r\n at Swashbuckle.Swagger.SwaggerGenerator.CreatePathItem(IEnumerable1 apiDescriptions, SchemaRegistry schemaRegistry)\r\n at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)\r\n at Swashbuckle.Swagger.SwaggerGenerator.GetSwagger(String rootUrl, String apiVersion)\r\n at Swashbuckle.Application.SwaggerDocsHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Net.Http.HttpMessageInvoker.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Web.Http.Dispatcher.HttpRoutingDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n at System.Web.Http.Cors.CorsMessageHandler.d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at U4.PublicApiFramework.Core.MessageHandlers.NotMatchedUriMessageHandler.d__3.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.HttpServer.d__0.MoveNext()"} http://localhost/agrtest-BusinessWorld-web-api/documentation/swagger/v1

STEPS TO REPRODUCE:

Opening up the site http://localhost/agrtest-BusinessWorld-web-api/swagger/ui/index

EXPECTED RESULT:

Swagger document should be displayed

ACTUAL RESULT:

The above error message is being displayed

[andrewzamer]

We were able to get the issue resolved by modifying the file set slightly

[ravideepbansal]

Hi Andrew, I am facing same issue. what did you change or how did you fix it?

[andrewzamer]

Hi @ravideepbansal ,
It almost looks like any API-related change done to the file set makes it work again for us. I simply deleted an unneeded file from our \Web Api\bin folder and restarted the WebAPI app pool and it worked for us.