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Calculator help

Posted on 2014-02-23
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Last Modified: 2014-02-23
I am getting errors on the line decimal result = Convert.ToDecimal(txtResult.Text);. It says input string is not in the correct format. I am new to C# so, any help would be appreciated. Thanks in advance.

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

namespace Calculator
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.Load += new EventHandler(Form1_Load);
        }
        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnCalculate_Click(object sender, EventArgs e)
        {
            decimal operand1 = Convert.ToDecimal(txtOperand1.Text);
            decimal operand2 = Convert.ToDecimal(txtOperand2.Text);
            decimal result = Convert.ToDecimal(txtResult.Text);
            
            string operator1 = txtOperator.Text;

            if (operator1 == "+")
            {
                result = operand1 + operand2;
                
            }

            else if (operator1 == "-")
	        {
		        result= operand1-operand2;
                
	        }
            else if (operator1 == "*")
	        {
                result = operand1 * operand2;
               
	        }
            else if (operator1 == "/")
            {
                result = operand1 / operand2;
             
            }

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

    }
}

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0
Comment
Question by:ryanbecker24
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4 Comments
 
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 39881290
The result is being calculated, so you should be outputting it, not reading it in from the form.

Change:
        private void btnCalculate_Click(object sender, EventArgs e)
        {
            decimal operand1 = Convert.ToDecimal(txtOperand1.Text);
            decimal operand2 = Convert.ToDecimal(txtOperand2.Text);
            decimal result = Convert.ToDecimal(txtResult.Text);
            
            string operator1 = txtOperator.Text;

            if (operator1 == "+")
            {
                result = operand1 + operand2;
                
            }

            else if (operator1 == "-")
	        {
		        result= operand1-operand2;
                
	        }
            else if (operator1 == "*")
	        {
                result = operand1 * operand2;
               
	        }
            else if (operator1 == "/")
            {
                result = operand1 / operand2;
             
            }

        }

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To:
        private void btnCalculate_Click(object sender, EventArgs e)
        {
            decimal operand1 = Convert.ToDecimal(txtOperand1.Text);
            decimal operand2 = Convert.ToDecimal(txtOperand2.Text);            
            string operator1 = txtOperator.Text;

            decimal result;
            if (operator1 == "+")
            {
                result = operand1 + operand2;
                
            }

            else if (operator1 == "-")
	        {
		        result= operand1-operand2;
                
	        }
            else if (operator1 == "*")
	        {
                result = operand1 * operand2;
               
	        }
            else if (operator1 == "/")
            {
                result = operand1 / operand2;
             
            }

            txtResult.Text = result.ToString();
        }

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*That error will occur for "operand1" and "operand2" if the value in the TextBox cannot be converted to a proper decimal.  To prevent that type of error, use Decimal.TryParse().
0
 

Author Comment

by:ryanbecker24
ID: 39881303
Thanks, but txtResult.Text = result.ToString() isn't working. It is saying use of unassigned local variable, but its being used though. Also, I don't understand what you mean with the asterisk. Sorry, for all the questions
0
 
LVL 86

Accepted Solution

by:
Mike Tomlinson earned 2000 total points
ID: 39881311
Just give your result variable an initial value:

    decimal result = 0.0;
0
 

Author Comment

by:ryanbecker24
ID: 39881425
Thank you
0

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