Can someone please help me with An unhandled exception in Conversion code

[johnkelly11]

Hi

can someone help me with this error in microsoft visual studio for the following code.

An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll

I think it occurs at

decimal conversion1 = Convert.ToDecimal(txtConversion1.Text);

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 Conversions
{
    public partial class Conversions : Form
    {
 
        string[,] lengths = {
                                   {"Select conversion"," "," "," "},                       // 2D array to Load comboBox with lenghts
                                   {"Miles to Kilometers","Miles","Kilometers","1.6093"}, 
                                   {"Kilometers to Miles","Kilometers","Miles","0.6214"},
                                   {"Feet to Metres","Feet","Metres","0.3048"},
                                   {"Metres to Feet", "Metres", "Feet", "3.2808"},
                                   {"Inches to Centimetres", "Inches", "Centimetres","2.54"},
                                   {"Centimetres to Inches", "Centimetres", "Inches", "0.3937"}
                               };
        public Conversions()
        {
            InitializeComponent();
 
            for (int i = 0; i < lengths.GetLength(0); i++)
            {
                comboBox1.Items.Add(lengths[i, 0]);
            }
            comboBox1.SelectedIndex = 0;
        }
 
        private void btnCalculate_Click(object sender, EventArgs e)
        {
            int selectedIndex = comboBox1.SelectedIndex;               // select element in comboBox
            decimal convrate = Convert.ToDecimal(lengths[selectedIndex, 3]);
            decimal conversion1 = Convert.ToDecimal(txtConversion1.Text);
            decimal result = conversion1 * convrate;
            txtConversion2.Text = result.ToString("n");
        }
 
        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }
 
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            int selectedIndex = comboBox1.SelectedIndex;
            lblConversion1.Text = lengths[selectedIndex, 1];
            lblConversion2.Text = lengths[selectedIndex, 2];
            txtConversion1.Text = "";
            txtConversion2.Text = "";
        }
    }
}
 
 

thanks

[arie]

This exception means that: "value is not a number in a valid format."

You have to check what exactly is in your txtConversion1.Text at the moment of convertsion. Set a breakpoint there and find out. The string you're trying to convert may be invalid, or empty.