HttpUtility.UrlDecode Method (String)
Converts a string that has been encoded for transmission in a URL into a decoded string.
Assembly: System.Web (in System.Web.dll)
If characters such as blanks and punctuation are passed in an HTTP stream, they might be misinterpreted at the receiving end. URL encoding converts characters that are not allowed in a URL into character-entity equivalents; URL decoding reverses the encoding. For example, when embedded in a block of text to be transmitted in a URL, the characters < and > are encoded as %3c and %3e.
To encode or decode values outside of a web application, use the WebUtility class.