Common Regular Expression Patterns for C#

Email id validation

Regular expression:

1. /^\w+([-+.’]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/ (Email Id)
2. /^([\w-\.]+@(?!gmail.com)(?!yahoo.com)(?!hotmail.com)([\w- ]+\.)+[\w-]{2,4})?$/ (free/domain specific email id)

URL validation

Regular expression:

1. /(http(s)?://)?([\w-]+\.)+[\w-]+[.com]+(/[/?%&=]*)?/ (with or without http)
2. /((www\.|(http|https|ftp|news|file)+\:\/\/)[_.a-z0-9-]+\.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\’|\# |!|\(|?|,| |>|<|;|\)])/( valid everywhere)

Password strength validation

Regular expression:

1. / ^[a-z0-9\.@#\$%&]+$/ (only contains letter [a-z] digits[0-9], special characters(@#$%&))
2. / ^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$/ (Minimum 8 characters at least 1 Alphabet and 1 Number)
3. / ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$@$!%*?&])[A-Za-z\d$@$!%*?&]{8,}/ (Minimum 8 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet, 1 Number and 1 Special Character)
4. / ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$@$!%*?&])[A-Za-z\d$@$!%*?&]{8,10}/ (Minimum 8 and Maximum 10 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet, 1 Number and 1 Special Character)
5. / ^[a-zA-Z0-9\s]{7,16}$/ (Minimum length 7 and Maximum length 16 Characters allowed [a–z] [A-Z] [0-9])

Mobile number validation

Regular expression:

1. / ^((\+){0,1}91(\s){0,1}(\-){0,1}(\s){0,1}){0,1}9[0-9](\s){0,1}(\-){0,1}(\s){0,1}[1-9]{1}[0-9]{7}$/ (without +91 or 0)
2. /^((\\+91-?)|0)?[0-9]{10}$/ (with or without +91 or 0)
3. ^((\\+|00)(\\d{1,3})[\\s-]?)?(\\d{10})$/ (split the number and the country code)

String pattern validation

Regular expression:

1. /(?s)^((?!manish).)*$/ (string contains manish)
2. \d/ (at list one digit )
3. /(.)*(\\d)(.)* / (contains number)
4. /^\d$/ (contains only number )
5. /^\d{11}$/ (contains only 11 digit number )
6. /^[a-zA-Z]+$/ (contains only letter )
7. /^[a-zA-Z0-9]+$/ (contains only letter and number )

Use of the regular expressions

Use the preceding regular expressions in the following ways.

In the following example, I am showing an email validation in various ways. Just replace the regular expression and use any of the others to use another validation.

Using JavaScript

1. “text/javascript”>
2.          function validateEmailId(email) {
3.              var reg = regular expression above pattern
4.              if (reg.test(email)) {
5.                  mesg.innerHTML = “”;
6.                  return true;
7.              }
8.              else {
9.                  mesg.style.color = “red”;
10.                  mesg.innerHTML = “Please provide a valid email address”;
11.                  return false;
12.              }
13.          }
14.     

Call the preceding method like.

Email Address:

1. <asp:TextBox ID=“txtemail” runat=“server” onblur=“validateEmailId(this.value)”></asp:TextBox>
2. <span id=“mesg” style=“font-size: small; position: relative;”>
3.  </span>

Using C# server-side

Using a normal function:

ASP.NET

 

• Email Address

 

1. <asp:TextBox ID=“txtemail” runat=“server” ></asp:TextBox>
2.     <asp:Label ID=“lblmsg” runat=“server” ></asp:Label>
3.     <br/>
4.     <asp:Button ID=“btnsubmit” runat=“server” Text=“Submit”
5.         onclick=“btnsubmit_Click”  />

• C#

 

1. private bool validateEmailId(string emailId)
2. {
3.    return Regex.IsMatch
4.    (
5.       emailId,
6.       @“^\w+([-+.’]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$”,
7.       RegexOptions.IgnoreCase
8.    );
9. }

• Call the preceding function in a button click.

 

1. protected void btnsubmit_Click(object sender, EventArgs e)
2. {
3.    if (validateEmailId(txtemail.Text.Trim()))
4.    {
5.       lblmsg.Text = string.Empty;
6.    }
7.    else
8.    {
9.       lblmsg.Text = “Please provide a valid email address”;
10.       lblmsg.ForeColor = System.Drawing.Color.Red;
11.    }
12. }

Using RegularExpressionValidator

ASP.NET

• Email Address:

 

1. <asp:TextBox ID=“txtemail” runat=“server” ></asp:TextBox>
2.     <asp:RegularExpressionValidator ID=“RegularExpressionValidator1” runat=“server”
3.         ErrorMessage=“Please provide a valid email address”
4.         ToolTip=“Please provide a valid email address”
5.         ValidationExpression=“^\w+([-+.’]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$”
6.         ControlToValidate=“txtemail” ForeColor=“Red”>Please provide a valid email address</asp:RegularExpressionValidator>

Using CustomValidator

ASP.NET

• Scripts

 

1. “text/javascript”>
2.         function validateEmailId(oSrc, args) {
3.             if (args.Value > 0) {
4.                 args.IsValid = (args.Value.match(/^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/));
5.             }
6.         }
7.     

• Email Address:

 

1. “text/javascript”>
2.         function validateEmailId(oSrc, args) {
3.             if (args.Value > 0) {
4.                 args.IsValid = (args.Value.match(/^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/));
5.             }
6.         }
7.     
8.    Email Address:
9.     <asp:TextBox ID=“txtemail” runat=“server” ></asp:TextBox>
10.     <asp:CustomValidator ID=“CustomValidator1” runat=“server”
11.         ErrorMessage=“Please provide a valid email address”
12.         ClientValidationFunction=“validateEmailId” ControlToValidate=“txtemail”
13.         Display=“Dynamic” ForeColor=“Red”
14.         ToolTip=“Please provide a valid email address”>Please provide a valid email address</asp:CustomValidator>

Change the preceding regular expression in case you need to use another expression.

Use regular expression with Linq:

Regex.Match(hrefValue, @”^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$”).Success

Using MVC:

Data Annotations

Suppose we have a student class like follows:

1. public partial class tblstudent
2. {
3.    public string Studentname { get; set; }
4.    public string Emailid { get; set; }
5. }

We can apply a regular expression like:

1. [RegularExpression(@“^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$”, ErrorMessage = “Please provide a valid email address”)]
2. public string Emailid { get; set; }

We can also extract a word or group of words from a string using a regular expression.

Suppose we want to extract a domain name and user name from an email id, then by using the following method we can do it.

Using C#:

1. string hrefValue = txtemail .Text .Trim ();
2. Match m = Regex.Match(hrefValue, @“^(\w+([-+.’]\w+)*)@(\w+([-.]\w+)*\.\w+([-.]\w+)*)$”);
3.             Response.Write(string .Format (“UserName : {0}”,  m.Groups[1].Value));
4.             Response.Write(“<br/>”);
5.             Response.Write(string.Format(“Domain : {0}”,  m.Groups[3].Value));

Using JavaScript:

1. “text/javascript”>
2.          function validateEmailId(email) {
3.              var reg = /^(\w+([-+.’]\w+)*)@(\w+([-.]\w+)*\.\w+([-.]\w+)*)$/;
5.              var matches = email.match(reg);
6.              UserId.innerHTML =‘UserName : ‘+ matches[1];
7.              Domain.innerHTML =‘Domain : ‘+  matches[3];
8.          }
9.