Automatically Hyperlink URLs and E-Mail Addresses in ASP.NET Pages with C#

Introduction

This article introduces how to hyperlink URLs and e-mail addresses in ASP.NET pages with C#, When you design a forum or other Web site, the code is very useful.

Background

After I designed the Web site http://www.outsourcexp.com, I found that many users post URL and e-mail information, but these URLs and e-mails just display as text. If you want to visit these URLs or e-mail addressess, you have to copy them and then paste them to your browser or e-mail client. I searched articles about automatically hyperlinking URLs, but only found VB source code. So, I decided do it myself.

Using the Code

The first step is how to detect URLs and e-mail addresses. Of course, the best way is with regular expressions. By using regular expressions, you can automatically detect hyperlink-sensitive text and automatically wrap it into elements pointing to the same URL. Here's how to proceed. The idea is to preprocess any displayable text using ad hoc regular expressions to identify portions of text that are e-mail addresses or Web site URLs. You create a RegEx object and initialize it with the regular expression. Next, you call IsMatch on the input string to see whether at least one match is found. Next, you call the Replace method. Replace takes the input as its first argument.

First, when you use regular expressions, you must include System.Text.RegularExpressions:

using System.Text.RegularExpressions;

The second step is to detect a URL:

Regex urlregex = new Regex(@"(http:\/\/([\w.]+\/?)\S*)",
   RegexOptions.IgnoreCase|RegexOptions.Compiled);

Here is how to detect an e-mail address:

Regex emailregex = new Regex(@"([a-zA-Z_0-9.-]+\@[a-zA-Z_0-9.-]+\.\w+)",
   RegexOptions.IgnoreCase|RegexOptions.Compiled);

When you detect a URL or e-mail address, you need to replace it with <a href=...></a>. I put all these into a function.

private void Button1_Click(object sender, System.EventArgs e)
{
   string strContent = InputTextBox.Text;
   Regex urlregex = new Regex(@"(http:\/\/([\w.]+\/?)\S*)",
                    RegexOptions.IgnoreCase| RegexOptions.Compiled);
   strContent = urlregex.Replace(strContent, 
                "<a href=\"$1\" target=\"_blank\">$1</a>");
   Regex emailregex = new Regex(@"([a-zA-Z_0-9.-]+\@[a-zA-Z_0-9.-]+\.\w+)",
      RegexOptions.IgnoreCase| RegexOptions.Compiled);
   strContent = emailregex.Replace(strContent, "<a href=mailto:$1>$1</a>");
   lbContent.Text += "<br>"+strContent;
}

Here you go. Build this control library, add references to your project, and enjoy validating.



About the Author

Roland Luo

I am a programmer who work for Offshore Outsourcing Inc. as well as run my own website, Outsourcing Software Development , which is a good place for freelancing activities,this website help people outsource software development to India,China or other countries, find freelance programmers and web designers all over the world. Started out doing Classic ASP, and moved on from there. My skillset now encompasses ASP, ASP.NET / C#, C++, VC++, MFC, SQL Server.

Downloads

Comments

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Live Event Date: October 29, 2014 @ 11:00 a.m. ET / 8:00 a.m. PT Are you interested in building a cognitive application using the power of IBM Watson? Need a platform that provides speed and ease for rapidly deploying this application? Join Chris Madison, Watson Solution Architect, as he walks through the process of building a Watson powered application on IBM Bluemix. Chris will talk about the new Watson Services just released on IBM bluemix, but more importantly he will do a step by step cognitive …

  • It's no secret what keeps CIOs up at night. Mobile, cloud, data, security, and social have become the "five imperatives," the drivers of business progress, innovation, and competitive differentiation. Business leaders around the world want to hear how other companies are succeeding. How are they applying the latest technologies? How did they get started? What outcomes are they achieving? Read this online magazine for success stories from organizations like the NBA, Pfizer, and San Jose State University as they …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds