Conversion program storing information in array and using a combobox

Question

This is homework (I always try to point that out so it's up front). The program is a conversion program. The user picks a conversion option from a combo box and then enters a length (ie: Feet to meters) when the user hits calculate the program calculates the conversion. I have several questions because the array part is confusing me. I wanted to make sure I am going in the right direction.

I think I am using my array to populate my combo box (I used an example provided although I do not fully understand it). When the user hits the calculate button should I be storing my conversion values in the same array? something like:

string [,] conversions = { {kilometers to miles, .11111}, {miles to kilometers, .11111}}

Or am I heading in the right direction with what I have? To be clear as it is coded the array populates my combobox so if I add the extra data then it will display those numbers in the combobox, which isn't really what I am going for.

My next question, when the user hits calculate button how is it going to know what option the user has selected? I think it has something to do with index but I'm confused as far as what is actually declaring it?

*****Disregard this question. I think I found an answer*********

Answer on Updating Labels

Finally I think my last question is the page has labels next to the textboxes so if the user chooses 'Miles to kilometers" the entry textbox is going to say Miles and then the answer textbox would say Kilometers... What is that called? I need to find it in my book and cannot. I know I'm missing something but I'm trying to find either an example or where in the book it was covered and I'm simply not seeing it.

Below is my code that I currently have.

public partial class FrmConversions : Form
{
    const double Miles_To_Kilometers = 1.6093;
    const double Kilometers_To_Miles = 0.6214;
    const double Feet_To_Meters = 0.3048;
    const double Meters_To_Feet = 3.2808;
    const double Inches_To_Centimeters = 2.54;
    const double Centimeters_To_Inches = 0.3937;

    public FrmConversions()
    {
        InitializeComponent();
    }


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


    private void FrmConversions_Load(object sender, EventArgs e)
    {
        cboConversions.Items.Clear(); //clear the combobox

        string[,] conversions =
            {
                {"Kilometers to Miles"  , "Miles to Kilometers"},
                {"Feet to Meters"       , "Meters to Feet"},
                {"Inches to Centimeters", "Centimeters to Inches"}
            };

        foreach (string str in conversions)
        {
            cboConversions.Items.Add(str);
        }
    }


    private void btnClear_Click(object sender, EventArgs e)
    {
        txtEntry.Clear();
        txtAnswer.Clear();
    }


    public bool IsDecimal(TextBox txtEntry, string name)
    {
        try
        {
            Convert.ToDecimal(txtEntry.Text);
            return true;
        }

        catch (FormatException)
        {
            MessageBox.Show(name + " must be a decimal value.", "Entry Error");
            txtEntry.Focus();
            return false;
        }
    }


    private void btnCalculate_Click(object sender, EventArgs e)
    {
        int index = cboConversions.SelectedIndex;
        if (index != -1)
        {
            try
            {
                if (IsDecimal())
                {
                    txtAnswer.Text = ToString;
                }

                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message + "\n\n" +
                    ex.GetType().ToString() + "\n" +
                    ex.StackTrace, "exception");
                }
            }
        }
    }
}


}

Brendan Hill Brendan Hill · Accepted Answer · 2013-10-31T00:19:24

There are many ways to do this, a Dictionary would be neat?

In this example, the Keys of the dictionary (the strings I specified) are loaded into the combo box. Later, those strings can be used to retrieve the conversion value from the dictionary.

// Declare at the top
Dictionary<string, double> conversions = {
    { "Kilometers to Miles", Kilometers_To_Miles},
    { "Miles to Kilometers", 1 / Kilometers_To_Miles},
    { "Feet to Meters", Feet_To_Meters},
    { "Meters to Feet", 1 / Feet_To_Meters},
etc
};

// In Form Load
foreach (string str in conversions.Keys)
{
    cboConversions.Items.Add(str);
}

// In btnCalculate_Click
var conversionValue = conversions[cboConversions.Text];
var convertedValue = (double)txtEntry.Text * conversionValue; // Need to validate is numeric
txtAnswer.Text = convertedValue

If you were hellbent on using arrays then this would work too, but cheats by using LINQ at the end:

// Declare at the top
object[,] conversions = {
    { "Kilometers to Miles", Kilometers_To_Miles},
    { "Miles to Kilometers", 1 / Kilometers_To_Miles},
    { "Feet to Meters", Feet_To_Meters},
    { "Meters to Feet", 1 / Feet_To_Meters},
etc
};

// In Form Load
foreach (string str in conversions)
{
    cboConversions.Items.Add(str[0]);
}

// In btnCalculate_Click
var conversionValue = conversions.First(x => x[0] == cboConventions.Text)[1];
var convertedValue = (double)txtEntry.Text * conversionValue; // Need to validate is numeric
txtAnswer.Text = convertedValue

Conversion program storing information in array and using a combobox

1 Answers