Uri escaping

 Posted by  Programming  Add comments  Tagged with:
Sep 102012

Either I need to download a certain page for further processing or I need to just post some data, code for generating url is quite similar. Just take two strings and merge them together. I usually then convert resulting string into Uri because most methods tend to require it, or even if they accept string, they convert it into Uri internally. For example:

var uriString = string.Format("http://www.example.com/{0}/", "ABC");
var uri = new Uri(uriString);
Debug.WriteLine(uriString + "\t" + uri.ToString());
// http://www.example.com/ABC/    http://www.example.com/ABC/

This, of course, does not deal with having special characters. All you need for those is escaping. Fortunately Uri class already has a method for that:

var uriString = string.Format("http://www.example.com/{0}/", Uri.EscapeDataString("A/BC"));
var uri = new Uri(uriString);
Debug.WriteLine(uriString + "\t" + uri.ToString());
// http://www.example.com/A%2FBC/  http://www.example.com/A/BC/

As you can see peculiar thing happened. While our string is escaped, transforming it to Uri actually loses this. Instead of encoded “A%2FBC” as one segment we get separate “A” and “BC”. Querying server with later will not result in expected content.

Solution here is to use double escaping.

var uriString = string.Format("http://www.example.com/{0}/", Uri.EscapeDataString(Uri.EscapeDataString("A/BC")));
var uri = new Uri(uriString);
Debug.WriteLine(uriString + "\t" + uri.ToString());
// http://www.example.com/A%252FBC/    http://www.example.com/A%252FBC/

End result might look ugly but it will get you that page every time.

P.S. Example.com does not contain said directories/files. To see double encoding example, you can check this link toward DigiKey (http://www.digikey.com/product-detail/en/DS2482S-100%252B/DS2482S-100%252B-ND/1197435) or just roll your own.

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