ServiceStack: Keep getting HTTP 500 errors for unknown reason - servicestack

Question

All of a sudden, I keep getting HTTP 500 errors in my self-hosted ServiceStack WS.
I have several requests already in place and they are working fine, but this one just wont work. I have added my license like this:
private void StartServiceStackService()
{
Licensing.RegisterLicenseFromFileIfExists("servicestack-license.txt".MapHostAbsolutePath());
_serviceStackHost = new ServiceStackWsHost(this, _frontEndModuleParameters, _alfaWebServicesSettings);
_serviceStackHost.Init();
if (!Debugger.IsAttached)
{
_serviceStackHost.Start(new[] { "http://+:8080/" });
}
else
{
_serviceStackHost.Start(new[] { "http://+:8081/" });
}
}
And the failing service is:
[Route(Bookings.BASE_PATH + "search", Verbs = "GET")]
public class SearchAddress : IReturn<SearchAddressResponse>
{
public string SearchString { get; set; }
}
public class SearchAddressResponse : ResponseBase
{
public string Test { get; set; }
// public List<Address> Addresses { get; set; }
}
internal class SearchAddressHandler : ServiceHandlerBase
{
public SearchAddressResponse Get(SearchAddress searchAddress)
{
return new SearchAddressResponse()
{
Test = "ASDASDASD"
};
}
}
And I call it using Fiddler4 like this:
GET http://192.168.0.147:8081/alfaonline/bookings/search?SearchString=123 HTTP/1.1
User-Agent: Fiddler
Host: 192.168.0.147:8081
AuthToken: a18b613c-23b2-4f4e-8934-ad8d6cbc57bb
DeviceUUID: 1baaace
and get this reply:
HTTP/1.1 500 Internal Server Error
Transfer-Encoding: chunked
Content-Type: text/html
Vary: Accept
Server: Microsoft-HTTPAPI/2.0
X-Powered-By: ServiceStack/5.20 Net45/Windows
Date: Wed, 26 Sep 2018 11:28:31 GMT
0
If I instead return "null", like this:
[MyAuthenticate]
internal class SearchAddressHandler : ServiceHandlerBase
{
public SearchAddressResponse Get(SearchAddress searchAddress)
{
return null;
}
}
Fiddler gives me HTTP 204 OK:
HTTP/1.1 204 OK
Content-Length: 0
Vary: Accept
Server: Microsoft-HTTPAPI/2.0
X-Powered-By: ServiceStack/5.20 Net45/Windows
Date: Wed, 26 Sep 2018 11:26:29 GMT
I see no errors, exceptions in VS in debug mode and "catch all" in Exception settings. I can put a breakpoint in the handler, and it breaks there, so the correct handler is executed.
UPDATE I have always been using Fiddler, now running Fiddler4. When I try the service, described below, in for example swagger (plugin to ServiceStack), it runs as expected. If I run the service in Postman, it runs as expected. But if I run it in Fiddler, I get HTTP 500
UPDATE 2 I also just noticed that going to http://127.0.0.1:8081/requestlogs also yields HTTP 500 error. More specifically, when I access /requestlogs and add the UncaughtExceptionHandlers, I see this error:
System.MissingMethodException: Method not found: 'System.String
ServiceStack.StringUtils.HtmlEncodeLite(System.String)'. at
ServiceStack.Formats.HtmlFormat.d__10.MoveNext()
at
System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine&
stateMachine) at
ServiceStack.Formats.HtmlFormat.SerializeToStreamAsync(IRequest req,
Object response, Stream outputStream) at
ServiceStack.HttpResponseExtensionsInternal.d__7.MoveNext()

Answer 1

Your first approach should be to get information about the Error:
Include a ResponseStatus property in your Response DTO if not already,
Enable Config.DebugMode
Add Debug Logging
Register Exception Handlers.