Calculate value automatically when selecting a decimal in combobox

Question

Im trying to get the selected value of my 4 comboboxes and add them together automatically in a windows form. The comboboxes items are decimals, 0,75 , 0,8 etc. How do i add all the values selected from the comboboxes together into a textbox?

I have tried for 5 hours now and really cant figure it out. FYI im really a beginner.

Thanks!

Even better yet switch to NumericUpDown controls which will return the value already cast to a number — tinstaafl
– tinstaafl, Commented Oct 12, 2016 at 17:48

ivayle · Accepted Answer · 2016-10-12 17:57:50Z

1

You can handle TextChanged event on all combo boxes, calculate the sum and assign the result to the text box.

private void Form1_Load(object sender, EventArgs e)
{
    foreach (var comboBox in this.Controls.OfType<ComboBox>())
    {
        comboBox.TextChanged += ComboBox_TextChanged;
        InitializeComboBox(comboBox);
    }
}

private void ComboBox_TextChanged(object sender, EventArgs e)
{
    double result = 0;
    foreach (var comboBox in this.Controls.OfType<ComboBox>())
    {
        if (!string.IsNullOrEmpty(comboBox.Text))
        {
            result += Convert.ToDouble(comboBox.Text);
        }
    }

    textBox1.Text = result.ToString();
}

private void InitializeComboBox(ComboBox comboBox)
{
    for (int index = 0; index < 10; index++)
    {
        comboBox.Items.Add(index + 0.5);
    }
}

edited Oct 12, 2016 at 17:57

answered Oct 12, 2016 at 17:49

ivayle

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2 Comments

R.B Over a year ago

I had a problem though, i got 2 more comboboxes in my form that i DONT want to add to the calculation but they seem to go in there anyways! :)

ivayle Over a year ago

You can exclude the additional two combo boxes via filtering the query using Where lambda expression. gist.github.com/ivayle/…

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