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asp net 4.61 WebAPI - Error catching

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User-1668014665 posted

TESTING in POSTMAN - Chrome App

The URL below works fine, and errors around this URL design I can catch

http://localhost:49327/api/data?Symbol=AAPL

Question1 how can I tidy up the ugly error reports when a User makes a mistake like this
http://localhost:49327/api/

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>IIS 10.0 Detailed Error - 404.0 - Not Found</title> <style type="text/css"> <!-- body{margin:0;font-size:.7em;font-family:Verdana,Arial,Helvetica,sans-serif;} code{margin:0;color:#006600;font-size:1.1em;font-weight:bold;} .config_source code{font-size:.8em;color:#000000;} Etc etc

Gives a 404, do I create a webconfig custom error HTML page or something??

Question2 How does catch this error, a variable is Not entered on the URL
http://localhost:49327/api/data?symbol=

After Symbol= there is nothing,

in Code Symbol is a string

Checking for Symbol ="" in code does not catch this error, can there be a NULL Check or something else

Thanks
Monday, March 4, 2019 10:51 PM

Answers

User1120430333 posted

I use a filter to catch all unhandled exceptions, which means there are no try/catch in the WebAPI or a classlib project code the WebAPI is referencing, and it's all caught by the global exception handler.

https://stackify.com/csharp-catch-all-exceptions/

The exception was caught and logged by that WebAPI, but the ASP.NET MVC project the presentation layer that used the WebAPI also had the exception returned. The MVC project knew about the exception that was thrown by the WebAPI, and it too threw an exemption so that its GEH logged the error and notified the user at the screen that something bad had happened.

Imports System.Net
Imports System.Net.Http
Imports System.Web.Http.Filters
Imports log4net

Public Class CustomExceptionFilter
    Inherits ExceptionFilterAttribute

    private ReadOnly _logger As ILog

    public sub New()
        _logger = LogManager.GetLogger(GetType(CustomExceptionFilter))
    End sub

    Public Overrides Sub OnException(actionExecutedContext As HttpActionExecutedContext)
        MyBase.OnException(actionExecutedContext)

        Dim exceptionMessage as String = String.Empty

        If IsNothing(actionExecutedContext.Exception.InnerException ) Then
            exceptionMessage = actionExecutedContext.Exception.Message _
                               & " " & actionExecutedContext.Exception.StackTrace
        Else 
            exceptionMessage =  actionExecutedContext.Exception.Message _
                                & " " & actionExecutedContext.Exception.InnerException.Message _
                                & " " & actionExecutedContext.Exception.StackTrace
        End If

        _logger.Error(exceptionMessage)

        dim response =  New HttpResponseMessage(HttpStatusCode.InternalServerError)With {.Content = New StringContent(“An unhandled exception was thrown by service.”),
                .ReasonPhrase = "Internal Server Error.Please Contact your Administrator."}

        actionExecutedContext.Response = response

    End Sub
End Class

Imports System.Web.Http
Imports DAL
Imports Entities

Namespace Controllers

    <CustomExceptionFilter>
    Public Class ProjectController
        Inherits ApiController

        Private ReadOnly _daoproject As IDaoProject

        public sub New (daoproject As IDaoProject)
            _daoproject = daoproject
        End sub

        <HttpGet>
        <ActionName("GetProjectById")>
        public Function GetProjectById(ByVal id As Int32) As DtoProject
            return _daoproject.GetProjectById(id)
        End Function


        <HttpGet>
        <ActionName("GetProjectsByUserId")>
        public Function GetProjectsByUserId(ByVal userid As String) As List(Of DtoProject)
            return _daoproject.GetProjectsByUserId(userid)
        End Function

        <HttpPost>
        <ActionName("CreateProject")>
        public sub CreateProject(ByVal dto As DtoProject)
            Call _daoproject.CreateProject(dto)
        End sub
        
        <HttpPost>
        <ActionName("UpdateProject")>
        public sub UpdateProject(ByVal dto As DtoProject)
            Call _daoproject.UpdateProject(dto)
        End sub

        <HttpPost>
        <ActionName("DeleteProject")>
        public sub  DeleteProject(ByVal dto As DtoId)
            Call _daoproject.DeleteProject(dto.Id)
        End sub
        
    End Class
End Namespace

Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM

Tuesday, March 5, 2019 12:16 AM

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Sign in to vote
User475983607 posted

TESTING in POSTMAN - Chrome App

The URL below works fine, and errors around this URL design I can catch

http://localhost:49327/api/data?Symbol=AAPL

Question1 how can I tidy up the ugly error reports when a User makes a mistake like this
http://localhost:49327/api/

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>IIS 10.0 Detailed Error - 404.0 - Not Found</title> <style type="text/css"> <!-- body{margin:0;font-size:.7em;font-family:Verdana,Arial,Helvetica,sans-serif;} code{margin:0;color:#006600;font-size:1.1em;font-weight:bold;} .config_source code{font-size:.8em;color:#000000;} Etc etc

Gives a 404, do I create a webconfig custom error HTML page or something??

Question2 How does catch this error, a variable is Not entered on the URL
http://localhost:49327/api/data?symbol=

After Symbol= there is nothing,

in Code Symbol is a string

Checking for Symbol ="" in code does not catch this error, can there be a NULL Check or something else

Thanks

The docs cover the basics.

https://docs.microsoft.com/en-us/aspnet/web-api/overview/error-handling/exception-handling

https://docs.microsoft.com/en-us/aspnet/web-api/overview/error-handling/web-api-global-error-handling

But yes, you can use filters to tidy up general errors.
Monday, March 4, 2019 11:51 PM