C# – Display custom error page when file upload exceeds allowed size in ASP.NET MVC

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My main issue is that I want to display an custom error page when an uploaded file exceeds allowed size (maxRequestLength in web.config).

When the big file is uploaded an HttpException is thrown before my upload action method in the controller is invoked. This is expected.

I have tried to catch the exception in a custom attribute and also to override OnException in the controller. Why isnt it possible to catch the exception in either the attribute or the OnException method?

Its possible though to catch the exception in Application_Error in global.asax but neither Response.Redirect nor Server.Transfer works for redirecting to the custom error page.
Server.Transfer gives the "failed to process child request" error and response.redirect gives the "Http headers already sent" error.

Any ideas?

Thanks in advance!

Marcus

Best Answer

When running under IIS7 and upwards there is another parameter:

<system.webServer>
  <security>
    <requestFiltering>
      <requestLimits maxAllowedContentLength="10485760" />
    </requestFiltering>
  </security>
</system.webServer>

The default setting is slightly less than 30 MB.

For uploaded files with size between maxRequestLength and maxAllowedContentLength IIS7 will throw an HttpException with HTTP code 500 and message text Maximum request length exceeded. When this exception is thrown, IIS7 kills the connection immediately. So an HttpModule that redirects on this error will only work if the HttpException is handled and cleared (using Server.ClearError()) in Application_Error() in global.asax.cs.

For uploaded files with size bigger than maxAllowedContentLength IIS7 will display a detailed error page with error code 404 and subStatusCode 13. The error page can be found in C:\inetpub\custerr\en-US\404-13.htm

For redirects on this error on IIS7 I recommend redirecting on httpErrors instead. To redirect to a different action set a smaller value for maxAllowedContentLength than maxRequestLength in web.config and also add the following to web.config:

<system.webServer>
  <httpErrors errorMode="Custom" existingResponse="Replace"> 
    <remove statusCode="404" subStatusCode="13" /> 
    <error statusCode="404" subStatusCode="13" prefixLanguageFilePath=""
       path="http://yoursite.com/Error/UploadTooLarge" responseMode="Redirect" /> 
  </httpErrors>
</system.webServer>

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Looking more closely at my web.config set up, one of the comments in this post is very helpful

in asp.net 3.5 sp1 there is a new parameter redirectMode

So we can amend customErrors to add this parameter:

<customErrors mode="RemoteOnly" defaultRedirect="~/errors/GeneralError.aspx" redirectMode="ResponseRewrite" />

the ResponseRewrite mode allows us to load the «Error Page» without redirecting the browser, so the URL stays the same, and importantly for me, exception information is not lost.

Asp.net-mvc – Routing for custom ASP.NET MVC 404 Error page

I've tried to enable custom errors on production server for 3 hours, seems I found final solution how to do this in ASP.NET MVC without any routes.

To enable custom errors in ASP.NET MVC application we need (IIS 7+):

Configure custom pages in web config under system.web section:
```
<customErrors mode="RemoteOnly"  defaultRedirect="~/error">
    <error statusCode="404" redirect="~/error/Error404" />
    <error statusCode="500" redirect="~/error" />
</customErrors>
```
RemoteOnly means that on local network you will see real errors (very useful during development). We can also rewrite error page for any error code.

Set magic Response parameter and response status code (in error handling module or in error handle attribute)

  HttpContext.Current.Response.StatusCode = 500;
  HttpContext.Current.Response.TrySkipIisCustomErrors = true;

Set another magic setting in web config under system.webServer section:
```
<httpErrors errorMode="Detailed" />
```

This was final thing that I've found and after this I can see custom errors on production server.

Best Answer

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