/// <summary>
/// Adds a middleware to the pipeline that will catch exceptions, log them, reset the request path, and re-execute the request.
/// The request will not be re-executed if the response has already started.
/// </summary>
/// <param name="app"></param>
/// <param name="errorHandlingPath"></param>
/// <returns></returns>
public static IApplicationBuilder UseErrorHandler(this IApplicationBuilder app, string errorHandlingPath)
{
var options = new ErrorHandlerOptions()
{
ErrorHandlingPath = new PathString(errorHandlingPath)
};
return(app.UseMiddleware <ErrorHandlerMiddleware>(options));
}
public ErrorHandlerMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, ErrorHandlerOptions options)
{
_next = next;
_options = options;
_logger = loggerFactory.CreateLogger<ErrorHandlerMiddleware>();
if (_options.ErrorHandler == null)
{
_options.ErrorHandler = _next;
}
}
public ErrorHandlerMiddleware(RequestDelegate next, ILogger <ErrorHandlerMiddleware> logger, IOptions <ErrorHandlerOptions> options)
{
if (options.Value.WebSettings == null)
{
throw new ArgumentNullException("WebSettings", "Unable to get WebSettings from the ErrorHandlerOptions");
}
_next = next;
_logger = logger;
_options = options.Value;
}
/// <summary>
/// Adds a middleware to the pipeline that will catch exceptions, log them, and re-execute the request in an alternate pipeline.
/// The request will not be re-executed if the response has already started.
/// </summary>
/// <param name="app"></param>
/// <param name="configure"></param>
/// <returns></returns>
public static IApplicationBuilder UseErrorHandler(this IApplicationBuilder app, Action <IApplicationBuilder> configure)
{
var subAppBuilder = app.New();
configure(subAppBuilder);
var errorPipeline = subAppBuilder.Build();
var options = new ErrorHandlerOptions()
{
ErrorHandler = errorPipeline
};
return(app.UseMiddleware <ErrorHandlerMiddleware>(options));
}
/// <summary>
/// API exceptions will return a JSON error message
/// Page exceptions will redirect to an error page based on the http status code in not Dev environments
/// </summary>
private static Task HandleExceptionAsync(HttpContext httpContext, Exception exception, ErrorHandlerOptions options, ILogger logger)
{
//this checks if we should rethrow the error to display in the development exception screen.
bool throwDevError = false;
string responseText = "";
EventId eventID;
if (exception is BaseException)
{
eventID = ((BaseException)exception).EventID;
}
else
{
eventID = new EventId();
}
try
{
int httpStatusCode = exception.GetStatusCode();
httpContext.Response.StatusCode = httpStatusCode;
//check if this is an API error or a Page error
if (httpContext.Request.Path.Value.StartsWith("/api/", StringComparison.OrdinalIgnoreCase))
{
//partial views will be expecting HTML but we are returning a JSON error message
httpContext.Response.ContentType = "application/json; charset=utf-8";
APIError error;
if (options.WebSettings.ShowErrors)
{
error = new APIError(exception);
}
else
{
error = new APIError();
}
error.Action = exception.GetAction();
//log error details
logger.LogError(eventID, exception, error.ReferenceNum.ToString() + " - " + exception.Message);
//create a JSON response for API error
responseText = error.ToString();
}
else
{
//get TempData handle
ITempDataDictionaryFactory factory = httpContext.RequestServices.GetService(typeof(ITempDataDictionaryFactory)) as ITempDataDictionaryFactory;
ITempDataDictionary tempData = factory.GetTempData(httpContext);
//pass reference number to error controller
Guid ReferenceNum = Guid.NewGuid();
tempData["ReferenceNumber"] = ReferenceNum.ToString();
//log error details
logger.LogError(eventID, exception, ReferenceNum.ToString() + " - " + exception.Message);
//handle Page error
if (options.WebSettings.ShowErrors)
{
throwDevError = true;
}
else
{
//if this was a page load redirect to the error page
httpContext.Response.Redirect("/Error/" + httpStatusCode.ToString("d"));
}
}
//track number of errors in this session
int errorCount = httpContext.Session.GetInt32(ERROR_COUNT_KEY).GetValueOrDefault();
httpContext.Session.SetInt32(ERROR_COUNT_KEY, ++errorCount);
options.LogErrorCallback?.Invoke(exception, httpContext, options.WebSettings, logger);
//if the max number is reached block user
if (options.WebSettings.MaxSessionErrors != null && options.WebSettings.MaxSessionErrors == errorCount)
{
options.MaxErrorCountCallback?.Invoke(httpContext, options.WebSettings, logger);
}
}
catch (Exception ex)
{
logger.LogCritical(ex.Message);
throw ex;
}
if (throwDevError)
{
throw exception;
}
return(httpContext.Response.WriteAsync(responseText));
}
public static IApplicationBuilder UseErrorHandling(this IApplicationBuilder app, ErrorHandlerOptions options)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
return(app.UseMiddleware <ErrorHandlerMiddleware>(Options.Create(options)));
}
/// <summary>
/// Insert a global error handler into the pipeline
/// </summary>
/// <param name="options">options.WebSettings cannot be null</param>
/// <returns></returns>
public static IApplicationBuilder UseErrorHandlerMiddleware(this IApplicationBuilder app, ErrorHandlerOptions options)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
//use dev page if we are returning detailed errors
if (options.WebSettings.ShowErrors)
{
app.UseDeveloperExceptionPage();
}
return(app.UseMiddleware <ErrorHandlerMiddleware>(Options.Create(options)));
}