Convert input in TextBox into decimal : TextBox « ASP.net Controls « ASP.NET Tutorial

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" 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>Simple Calculator</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h1>The Simple Calculator</h1>
        First number:
        <asp:TextBox ID="txtFirst" runat="server" />  
        <br /><br />
        Second number:
        <asp:TextBox ID="txtSecond" runat="server" />  
        <br /><br />
        <asp:Button ID="btnAdd" runat="server"   
            OnClick="btnAdd_Click" Text="Add" />
        <br /><br />
        The answer is:
        <asp:Label ID="lblAnswer" runat="server" />  
    </div>
    </form>
</body>
</html>

File: Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;


public partial class _Default : System.Web.UI.Page 
{
    protected void btnAdd_Click(object sender, EventArgs e)
    {
        decimal a = decimal.Parse(txtFirst.Text);
        decimal b = decimal.Parse(txtSecond.Text);
        decimal c = a + b;
        lblAnswer.Text = c.ToString();
    }
}

3.5.TextBox
	3.5.1.	Important properties, method and event of TextBox control
	3.5.2.	TextBox can display different types of input fields depending TextMode property
	3.5.3.	Show AutoComplete
	3.5.4.	Set the focus to a TextBox
	3.5.5.	Get input value from asp:textbox (VB.net)
	3.5.6.	Set textbox text value in button action
	3.5.7.	asp:TextBox changed event (C#)
	3.5.8.	Use if statement to check form input data (VB.net)
	3.5.9.	Bind string value to asp:textBox (VB.net)
	3.5.10.	Use Cint to convert input value in asp:textbox to integer (VB)
	3.5.11.	Use Convert.ToInt32 to convert input value in asp:textbox to integer (C#)
	3.5.12.	Check form input value and report error in case of empty input (VB.net)
	3.5.13.	Set AutoCompleteType
	3.5.14.	Convert input in TextBox into decimal
	3.5.15.	Extrapolate date values from the typed text