Question

Visual Studio 2010 – (Windows Forms) in C#

I have this code:

private void cbxValuta_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            string primo = cbxValuta.SelectedItem.ToString();
            string secondo = cbxValuta2.SelectedItem.ToString();
            double cambio = double.Parse(CurrencyConverter.Convert(1.0m, primo, secondo));
            tbxConvertito.Text = (double.Parse(tbxDaConvertire.Text) * cambio).ToString();

I get this error:

NullReferenceException was unhandled
Object reference not set to an instance of an object.

How Can I solve this issue?

Answer 1

SelectedItem return null if no item was selected in a UI element. Try to add check if items has been selected

if(cbxValuta.SelectedItem != null && cbxValuta2.SelectedItem != null)
{
       string primo = cbxValuta.SelectedItem.ToString();
       string secondo = cbxValuta2.SelectedItem.ToString();
//       ....
}