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10.27.06
Validating A URL With Regular Expressions
 By
Mads Kristensen
I had to build web form that took user input from standard ASP.NET input controls. In one of the text boxes the user must enter a valid URL, so I had to make some validation logic.
But first of all, I had to find out what kind of URL's we would accept as being valid. These are the rules we decided upon:
• The protocol must be http or https
• Sub domains are allowed
• Query strings are allowed
Based on those rules, I wrote this regular expression:
It is used in a RegularExpressionValidator control on the web form and on a business object in C#.
Here is the server-side validator method used by the business object:
You can add more protocols to the expression easily. Just add them to the beginning of the regular expression:
You can also allow every thinkable protocol containing at least 3 characters by doing this:
About the Author:
Mads Kristensen currently works as a Senior Developer at Traceworks located in Copenhagen, Denmark. Mads graduated from Copenhagen Technical Academy with a multimedia degree in 2003, but has been a professional developer since 2000. His main focus is on ASP.NET but is responsible for Winforms, Windows- and web services in his daily work as well. A true .NET developer with great passion for the simple solution. |
