I have an exception that says this: System.NullReferenceException when adding an item to a combobox

Question

I have an exception that says this:

System.NullReferenceException

when adding an item to a combobox with this code:

namespace Veterinari
{
    public partial class Diagnostico : Form
    {
        int tipo;

        public Diagnostico()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Principal prin = new Principal(tipo);
            prin.Show();
            this.Hide();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Principal prin = new Principal(tipo);
            prin.Show();
            this.Hide();
        }
    }
}

Please edit your post to include your code and the entire error message — Minijack, May 21 '19 at 04:33
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — vasily.sib, May 21 '19 at 04:35
Please format the code and also tell use which line of code gives the exception — Chetan, May 21 '19 at 04:36
That is still not the full Exception message. (does not include the stack trace) — Minijack, May 21 '19 at 04:53

score 0 · Answer 1 · answered May 21 '19 at 04:54

0

The int tipo is never instantiated.

This means that it will always be null until you set its value:

public Diagnostico()
{
    tipo = 0;
    InitializeComponent();
}

answered May 21 '19 at 04:54

Minijack

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I have an exception that says this: System.NullReferenceException when adding an item to a combobox

1 Answers1