Validating Email ID in TextBox in C# .Net

To validate a email id in textbox you can place this code in Validating event of textbox or in Leave event of textbox:

System.Text.RegularExpressions.Regex rEMail = new System.Text.RegularExpressions.Regex(@"^[a-zA-Z][\w\.-]{2,28}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$");

//txtmail is name/object of textbox
if (txtmail.Text.Length > 0){

//rEMail is object of Regex class located in System.Text.RegularExpressions
if (!rEMail.IsMatch(txtmail.Text))
{
MessageBox.Show("E-Mail expected", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
txtmail.SelectAll();
e.Cancel = true;
}

The regex classes are located in the namespace System.Text.RegularExpressions. To make them available, place Imports System.Text.RegularExpressions at the start of your source code.

REgex provide immutable expression. and u can use System.Text.RegularExpressions to find a valuie in a richtextbox like in notepad or in any other application.

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