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Error: Input String Was Not In Correct Format

Hi,

I have an app to add coins, they need to equal up to $2.00. If I enter in 8 quarters, which is 2 dollars and leave the pennies, nickels and dimes field blank, I get a  error: Input String Was Not In Correct Format.

Any clue why?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace CoinApplication
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void exitButton_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void clearButton_Click(object sender, EventArgs e)
        {
            pennyTextBox.Text = "";
            nickelTextBox.Text = "";
            dimeTextBox.Text = "";
            quarterTextBox.Text = "";
            totalValueLabel.Text = "";

            pennyTextBox.Focus();
        }

        private void calculateButton_Click(object sender, EventArgs e)
        {
            try
            {
                const decimal PENNY_VALUE = 0.01m;
                const decimal NICKEL_VALUE = 0.05m;
                const decimal DIME_VALUE = 0.10m;
                const decimal QUARTER_VALUE = 0.25m;
                const decimal TOTAL = 2.00m;
               decimal total = 0.0m;



                int totalPenny, totalNickel, totalDime, totalQuarter;

                totalPenny = int.Parse(pennyTextBox.Text);
                totalNickel = int.Parse(nickelTextBox.Text);
                totalDime = int.Parse(dimeTextBox.Text);
                totalQuarter = int.Parse(quarterTextBox.Text);

                if (totalPenny <=0)
                {
                    MessageBox.Show("Number of pennies must be greater than 0");
                }
                else 
                {
                    total += (totalPenny * PENNY_VALUE);       
                }
               if (totalNickel <=0)
                {
                    MessageBox.Show("Number of nickels must be greater than 0");               
                }
               else
               {
                   total += (totalNickel * NICKEL_VALUE);
               }

                if (totalDime <= 0)
                {
                    MessageBox.Show("Number of dimes must be greater than 0");   
                }
                else
                {
                    total += (totalDime * DIME_VALUE);
                }
                if (totalQuarter <= 0)
                {
                    MessageBox.Show("Number of quarters must be greater than 0");   
                    
                }
                else
                {
                    total += (totalQuarter * QUARTER_VALUE);
                }

                if (total == TOTAL)
                {
                    totalValueLabel.Text = total.ToString("c");
                    winnerLooserLabel.Text = ("Congrats");
                }
                else
                {

                    totalValueLabel.Text = total.ToString("c"); 
                    winnerLooserLabel.Text = ("Try Again");
                }

            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}

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Computer Guy
Asked:
Computer Guy
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1 Solution
 
käµfm³d 👽Commented:
As the documentation for int.Parse states:

In addition to decimal digits, only leading and trailing spaces together with a leading sign are allowed.

You need to test the value before you try to convert it. You can actually do both at the same time via int.TryParse.
0
 
Computer GuyAuthor Commented:
Ok, great!

This is what I came up with to replace it.
Two questions.

1. How do I handle invalid characters (letters, ect?
2. Is this clean / efficient code?

                const decimal PENNY = 0.01m;
                const decimal NICKEL = 0.05m;
                const decimal DIME = 0.10m;
                const decimal QUARTER = 0.25m;
                const decimal TOTAL = 2.00m;

                decimal total = 0m;


                int totalPenny, totalNickel, totalDime, totalQuarter;

                    if (int.TryParse(pennyTextBox.Text, out totalPenny) == true)
                    {
                        total += totalPenny * PENNY;
                    }

                    if (int.TryParse(nickelTextBox.Text, out totalNickel) == true)
                    {
                        total += totalNickel * NICKEL;
                    }

                    if (int.TryParse(dimeTextBox.Text, out totalDime) == true)
                    {
                        total += totalDime * DIME;
                    }

                    if (int.TryParse(quarterTextBox.Text, out totalQuarter) == true)
                    {
                        total += totalQuarter * QUARTER;
                    }
                    totalValueLabel.Text = total.ToString("c");

                    
                if (total == TOTAL)
                    {
                        MessageBox.Show("Congratulations, you have the correct number of coins");
                    }
                    else if (total > TOTAL)
                    {
                        MessageBox.Show("The number of coins you entered is more than " + TOTAL.ToString("c") + " Try again");
                    }
                    else if (total < TOTAL)
                    {
                        MessageBox.Show("The number of coins you entered is less than " + TOTAL.ToString("c") + " Try again");
                    }

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käµfm³d 👽Commented:
1. How do I handle invalid characters (letters, ect?
Show a MessageBox? Change the background color of the TextBox to red? It's up to you. What is your requirement?

2. Is this clean / efficient code?
It looks fine to me. Focus on readable code first. Worry about performance once it becomes an issue.
0
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Computer GuyAuthor Commented:
Should the box be per field? So if they enter in abc in nickel and dime it would show twice?
0
 
käµfm³d 👽Commented:
That's a decision you would have to make. But in terms of user experience, it would get tiresome having to click multiple MessageBox buttons every time I put in bad input. You might consider either tallying up all of the error messages, and then showing the complete list of errors in one MessageBox, or you might consider using the ErrorProvider, which gives indication of errors without really getting in the user's way.
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Computer GuyAuthor Commented:
Hi,

Ok, so I tried this and if it is null, it shows the message box. It does not need to be a required field. If the value is an integer or blank, do the math or if there are invalid characters, then show the message box.

                if (int.TryParse(pennyTextBox.Text, out totalPenny) == true)
                {
                    total += totalPenny * PENNY_VALUE;
                }
                else
                {
                    MessageBox.Show("Please enter a valid number of pennies.");
                }

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käµfm³d 👽Commented:
I don't understand the question.
0
 
Computer GuyAuthor Commented:
Ok. So with the code I recently posted
It shows the message box when the penny text box is empty or has a letter in it.

I don't want it to show the message box if there is nothing in the text box. Show only if it is a letter
0
 
käµfm³d 👽Commented:
if (!string.IsNullOrWhitespace(pennyTextBox.Text) && int.TryParse(pennyTextBox.Text, out totalPenny) == true)

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