UrlEncoding Plus(+) in URL in ASP.Net

Question

I'm encrypting and Base64 a string. Everything works great, until I retrieve the encrypted string from the QueryString collection. The Encrypted text contains a plus symbol. When I retrieve the encrypted string, where a plus once was there is now a space. As you can imagine this doesn't decrypt.

I have tried both Server.HtmlEncode/HtmlDecode and Server.UrlEncode/Server.UrlDecode with no avail. Both methods confuse the plus symbol with the space.

Any idea's?

Here is a similar post: QueryString Malformed

Edit: I found the solution: Server.UrlEncode does work, I was applying Server.UrlDecode and didn't need too.

Answer 1

Be careful, the method of substituting "+++" for "==" is dangerous because in rare situations, it is possible for an encrypted query string to validly contain "+++". In this case, the decryption fails. For a better solution to the problem, look at using the "modified base64 for url". It involves switching out "-" for "+" and "_" for "/" and has no "==" padding. It seems to be working for us, even in situations where the other failed. Here is the link I used for reference that is working for us.

Code for decoding/encoding a modified base64 URL