Server Error in '/' Application.

Sequence contains more than one matching element

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Sequence contains more than one matching element

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[InvalidOperationException: Sequence contains more than one matching element]
   System.Linq.Enumerable.Single(IEnumerable`1 source, Func`2 predicate) +338
   ServiceStack.WebHost.Endpoints.Metadata.BaseMetadataHandler.ProcessOperations(HtmlTextWriter writer, IHttpRequest httpReq, IHttpResponse httpRes) +325
   ServiceStack.WebHost.Endpoints.Support.HttpHandlerBase.ProcessRequest(HttpContext context) +47
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +3375
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +220
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +1361


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4700.0