Step 1: - Design Page
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplicationDemo.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server" AutoPostBack="true" OnTextChanged="TextBox1_TextChanged"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Search" OnClick="Button1_Click" />
</div>
</form>
</body>
</html>
Step 2: - Code behind Page
using System;
using System.Text.RegularExpressions;
using System.Web.UI;
namespace WebApplicationDemo
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void
Page_Load(object sender, EventArgs e)
{
}
protected void
TextBox1_TextChanged(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(TextBox1.Text))
{
if (Regex.IsMatch(TextBox1.Text, "[a-zA-Z]+$"))
{
ScriptManager.RegisterStartupScript(Page,
this.GetType(), "alert", "alert('You entered the " + TextBox1.Text + ".')", true);
}
else
{
ScriptManager.RegisterStartupScript(Page,
this.GetType(), "alert", "alert('Please enter only alphabet to search.')", true);
}
}
}
protected void
Button1_Click(object sender, EventArgs e)
{
if (string.IsNullOrEmpty(TextBox1.Text))
{
ScriptManager.RegisterStartupScript(Page, this.GetType(), "alert", "alert('Please enter text to
search.')", true);
return;
}
TextBox1_TextChanged(null, EventArgs.Empty);
}
}
}
