An interesting test came up recently where we needed to URL encode everything but the slashes in an URL.  What is the best way to handle this speed wise as well as memory wise.

Method 1: Split/Join.  Split the URL by ‘/’, loop through and UrlEncode the pieces then Join it back together with ‘/’

Method 2: Replace. Url encode then replace ‘%2f’ with ‘/’

Method 3: Split/Concat. Split the URL by ‘/’, loop through the and UrlEncode the pieces then concatenate them to a final string

Method 4: Split/StringBuilder.  Same as Method 3 but use a StringBuilder with append instead of +=.

I wanted to know the difference in memory usage as well as speed between the methods.  There are situations where memory overhead is more important than speed like when running code on a large, heavily used, internet web site hosting tens to hundreds of applications per server.  Well the only way to prove is to test it so we brought out the trusty profiler and created the four tests.

Each test ran 1 million loops.  The URL was the same on each loop

Notice that the test with StringBuilder actually took more clock cycles and more memory than all the rest.  Odd, at least I know that Replace kicks but now I’m wondering about efficiencies built into .NET when the URL is the same.  I’m going to need to test this again with a variable URL.