调用自定义WebApi

调用自定义WebApi出现的错误，是什么原因呢？ 求解

"response_error:Code(-2147467259);{\"InnerExWrapper\":{\"IsEmpty\":false,\"Data\":{},\"HelpLink\":null,\"Message\":\"索引和长度必须引用该字符串内的位置。\\r\\n参数名: length\",\"Source\":null,\"StackTrace\":\" 在 System.String.Substring(Int32 startIndex, Int32 length)\\r\\n 在 Kingdee.BOS.ServiceFacade.KDServiceFx.ServiceTypeManager.ReflectServiceType(String svcFullName)\",\"TargetSite\":null,\"ExceptionType\":\"System.ArgumentOutOfRangeException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\",\"InnerException\":null},\"ClassName\":\"Kingdee.BOS.ServiceFacade.ServiceException\",\"Message\":\"索引和长度必须引用该字符串内的位置。\\r\\n参数名: length\",\"Data\":null,\"InnerException\":null,\"HelpURL\":null,\"StackTraceString\":\" 在 Kingdee.BOS.ServiceFacade.KDServiceFx.ServiceTypeManager.ReflectServiceType(String svcFullName)\\r\\n 在 Kingdee.BOS.ServiceFacade.KDServiceFx.RequestExcuteRuntime.BeginRquest(RequestExtractor requestExtractor, WebContext webCtx)\\r\\n 在 Kingdee.BOS.ServiceFacade.KDServiceFx.RequestExcuteRuntime.StartRequest(RequestExtractor requestExtractor, WebContext context)\\r\\n 在 Kingdee.BOS.ServiceFacade.KDServiceFx.KDSVCHandler.ExecuteRequest(WebContext ctx, RequestExtractor requestExtractor)\\r\\n 在 Kingdee.BOS.ServiceFacade.KDServiceFx.KDSVCHandler.ProcessRequestInternal(WebContext webCtx, RequestExtractor requestExtractor)\",\"RemoteStackTraceString\":null,\"RemoteStackIndex\":0,\"ExceptionMethod\":\"8\\nReflectServiceType\\nKingdee.BOS.ServiceFacade.KDServiceFx, Version=7.0.104.1, Culture=neutral, PublicKeyToken=null\\nKingdee.BOS.ServiceFacade.KDServiceFx.ServiceTypeManager\\nKingdee.BOS.ServiceFacade.KDServiceFx.ServiceType ReflectServiceType(System.String)\",\"HResult\":-2147467259,\"Source\":\"Kingdee.BOS.ServiceFacade.KDServiceFx\",\"WatsonBuckets\":null,\"_httpCode\":500}"