replace %20 or space from url in C#.net

Question

Hi All,

i m using visual stdio version :2010 and framework :4.0 , i am willing to replace the space in url with - 

here is my code 

<rule name="Myrule3" stopProcessing="true">
                   <match url="(.)((%20)|\ )(.)" />
                   <action type="Rewrite" url="{R:1}-{R:4}" logRewrittenUrl="true" />
               </rule>

but the above rule is not effecting my url .. any help will be appreciated.

Thanks