Finding all words starting with "re" using regular expressions with .net
In this regular expression we are going to find all words starting with "re". Means we are going to search words beginning(first two character) will be "re".
Regular Expression Pattern
(\bre)\w+\b
A description of the regular expression:
[1]: A numbered capture group. [\bre]
\bre
First or last character in a word
re
\w+\b
Alphanumeric, one or more repetitions
First or last character in a word
Sucessful Matches
replace
regex
regular
How It Works
This regular expression will check for begining of a word followed by “re”, any Alphanumeric value, one or more repetitions with last character in a word.
If you want to match words like regex, Regex or RegEx you need to turn on Turn ON Ignore Case option. "(\b(?i)re)\w+\b" regex pattern will do it for you. Read more about Mode Modifiers – Using Regular Expressions Metacharacters with .net – Comments and Mode Modifiers
ASP.NET
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Finding all words starting with "re" using regular expressions</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<span>Valid Format: enter word start with "re" </span><br />
<asp:TextBox id="txtInput" runat="server"></asp:TextBox><br />
<asp:RegularExpressionValidator Id="vldRejex" RunAt="server" ControlToValidate="txtInput" ErrorMessage="word not start with re" ValidationExpression="^(\bre)\w+\b$">
</asp:RegularExpressionValidator><br />
<asp:Button Id="btnSubmit" RunAt="server" CausesValidation="True" Text="Submit"></asp:Button>
</div>
</form>
</body>
</html>
C#.NET
//use System.Text.RegularExpressions befour using this function
//using System.Text.RegularExpressions;
public bool vldRegex(string strInput)
{
//create Regular Expression Match pattern object
Regex myRegex = new Regex("^(\\bre)\\w+\\b$");
//boolean variable to hold the status
bool isValid = false;
if (string.IsNullOrEmpty(strInput))
{
isValid = false;
}
else
{
isValid = myRegex.IsMatch(strInput);
}
//return the results
return isValid;
}
VB.NET
‘Imports System.Text.RegularExpressions befour using this function
Public Function vldRegex(ByVal strInput As String) As Boolean
‘create Regular Expression Match pattern object
Dim myRegex As New Regex("^(\bre)\w+\b$")
‘boolean variable to hold the status
Dim isValid As Boolean = False
If strInput = "" Then
isValid = False
Else
isValid = myRegex.IsMatch(strInput)
End If
‘return the results
Return isValid
End Function
[...] Finding all words starting with "re" using regular expressions with .net [...]