How come the discount amount textbox and total price aren't calculating right?

Question

How come the discount amount textbox and total price aren't calculating right?

4.2k Views Asked by User445555 At 11 April 2025 at 03:26

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace XEx02Quotation
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
       
        protected void Button1_Click(object sender, EventArgs e)
        {
            if (IsValid)
            {
                int SalesPrice = Convert.ToInt32(TextBox1.Text);
                // When a user inputs an integer, I want it to be able to handle input of fractions
                // without getting an exception error. 



                // If a user inputs a whole number or fractional number (like 20.25), it should be able
                // to handle it.
                double DiscountPercentage = Convert.ToDouble(TextBox2.Text);
                

                double discountValue = this.CalculateDiscountValue(SalesPrice, DiscountPercentage);
                double TotalPrice = this.TotalPriceCalculate(SalesPrice, discountValue);
                Label1.Text = discountValue.ToString("c");
                Label2.Text = TotalPrice.ToString("c"); 
            
            }
        }
        protected double CalculateDiscountValue(int SalesPrice, double DiscountPercentage)
        {
           double discountAmount = SalesPrice * DiscountPercentage;
            return discountAmount; 
        }

        protected double TotalPriceCalculate(int SalesPrice, double discountAmount)
        {
            double TotalPrice = SalesPrice - discountAmount;
            return TotalPrice; 
        }


    }
        
}

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="XEx02Quotation.Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Price quotation</title>
    <style type="text/css">
        .auto-style1 {
            width: 54%;
            height: 213px;
        }
        .auto-style15 {
            width: 114px;
            height: 23px;
        }
        .auto-style16 {
            width: 114px;
        }
        .auto-style17 {
            width: 114px;
            height: 28px;
        }
        .auto-style18 {
            width: 193px;
            height: 23px;
        }
        .auto-style20 {
            width: 193px;
            height: 28px;
        }
        .auto-style21 {
            width: 193px;
        }
        .auto-style22 {
            margin-left: 12px;
        }
        .auto-style23 {
            margin-left: 16px;
        }
        .auto-style25 {
            width: 193px;
            height: 5px;
        }
        .auto-style26 {
            width: 114px;
            height: 5px;
        }
        .auto-style27 {
            width: 143px;
            height: 23px;
        }
        .auto-style28 {
            width: 143px;
            height: 5px;
        }
        .auto-style29 {
            width: 143px;
        }
        .auto-style30 {
            width: 143px;
            height: 28px;
        }
        .auto-style31 {
            width: 143px;
            height: 25px;
        }
        .auto-style32 {
            width: 193px;
            height: 25px;
        }
        .auto-style33 {
            width: 114px;
            height: 25px;
        }
    </style>
</head>
<body>

    <form id="form1" runat="server">
        
        <h1>Price quotation</h1>
        
        <br />
        <br />
        <table class="auto-style1">
            <tr>
                <td class="auto-style27">Sales Price</td>
                <td class="auto-style18">
                    <asp:TextBox ID="TextBox1" runat="server" CssClass="auto-style23" Width="173px" Font-Bold="True"></asp:TextBox>
                </td>
                <td class="auto-style15"></td>
            </tr>
            <tr>
                <td class="auto-style27"></td>
                <td class="auto-style18"></td>
                <td class="auto-style15"></td>
            </tr>
            <tr>
                <td class="auto-style27">Discount percent</td>
                <td class="auto-style18">
                    <asp:TextBox ID="TextBox2" runat="server" CssClass="auto-style22" Width="169px"></asp:TextBox>
                </td>
                <td class="auto-style15"></td>
            </tr>
            <tr>
                <td class="auto-style28">Discount amount</td>
                <td class="auto-style25">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;<asp:Label ID="Label1" runat="server" Font-Bold="True" Text="Label"></asp:Label>
                </td>
                <td class="auto-style26"></td>
            </tr>
            <tr>
                <td class="auto-style27"></td>
                <td class="auto-style18"></td>
                <td class="auto-style15"></td>
            </tr>
            <tr>
                <td class="auto-style30">Total price</td>
                <td class="auto-style20">
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                    <asp:Label ID="Label2" runat="server" Font-Bold="True" Text="Label"></asp:Label>
                </td>
                <td class="auto-style17"></td>
            </tr>
            <tr>
                <td class="auto-style31">
                    </td>
                <td class="auto-style32"></td>
                <td class="auto-style33"></td>
            </tr>
            <tr>
                <td class="auto-style29">
                    <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Calculate" Width="90px" />
                </td>
                <td class="auto-style21">&nbsp;</td>
                <td class="auto-style16">&nbsp;</td>
            </tr>
        </table>
        
    </form>

</body>
</html>

when I input the sales price in the textbox as a fraction (like 120.99) and enter an int number or double (like 15 or 20.2) into the discount percentage textbox, the discount amount and total price doesn't calculate right? Do I need to do explicit conversions with my variables? I am so confused. Here is code for ASP.NET web form in my web application. I am currently working within my Default.aspx.cs (C#) file (and I also have a Default.aspx file too).

Original Q&A

There are 1 best solutions below

**ashin** · Accepted Answer

As pointed out in the comments and in TaW's answer, you should be using decimal instead of int and the total price calculation misses division by 100. I have put everything together.

The click handler should be modified as follows:

 protected void Button1_Click(object sender, EventArgs e)
    {
        if (IsValid)
        {
            decimal salesPrice;
            decimal discount;

            if (decimal.TryParse(TextBox1.Text, out salesPrice))
            {
                if (decimal.TryParse(TextBox2.Text, out discount))
                {
                    decimal discountValue = this.CalculateDiscountValue(salesPrice, discount);
                    decimal totalPrice = this.TotalPriceCalculate(salesPrice, discount);

                    Label1.Text = discountValue.ToString("c");
                    Label2.Text = totalPrice.ToString("c");
                }
            }
        }
    }

And the helper methods as follows:

protected decimal CalculateDiscountValue(decimal salesPrice, decimal discountPercentage)
 {
    return salesPrice * discountPercentage / 100m;
 }

protected decimal TotalPriceCalculate(decimal salesPrice, decimal discountAmount)
 {
    return salesPrice - discountAmount;
 }

How come the discount amount textbox and total price aren't calculating right?

There are 1 best solutions below

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