Sometimes, the limitation on the upload size is at the other end, on the server. I'm not familiar with ASP, preferring to handle this sort of thing in PHP, where for instance the server can have a maximum upload size specified in the php.ini file; since my app allows users to upload files, which can be fairly large if not resized first, I had to change that to allow a larger file.
A quick google for similar settings on ASP.net turned up this link, which might be a useful starting point:
http://stackoverflow.com/questions/288612/how-to-increase-the-max-upload-file-size-in-asp-net
However, if you're allowing users to upload photos from their device camera, for example, then you're going to find you need to increase that every couple of years, as people get phones with ever higher resolutions, and users don't think about resizing.
So, you might want to think about scaling the image before uploading it; not only can you then do your best to ensure it stays within a reasonable size, but your app may seem more responsive, as a big file can take a long time to upload - and sometimes (perhaps counterintuitively) that seems worse when connected via WiFi, as a typical home DSL connection has a pretty slow upload speed. I often find it's quicker to upload on mobile data than from home.
If you scale the file, you can cut down on the time taken to upload, and probably give users more useful feedback than if you just change the settings on the server and then try to fling a huge file at it and hope for the best.