unable to handle null values in ComboBox ?

SUNIL GUTTA

Hie friends

Well i used a button and combo box . when i click on button it should display what ever i selected in combo box :) when i select something in comboBox its working fine but when i un-intentionally click on button without selecting anything in comboBox ITS THROWING me Null Reference Exception :(

How to handle this ? Is there any other way except exceptional handling ?

My Code :
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(comboBox1.SelectedItem.ToString());
}

(OR)

private void button1_Click(object sender, EventArgs e)
{
foreach(object obj in ComboBox1.SelectedItem.ToString())

MessageBox.Show(obj.ToString());
}

Foreach also failed to handle null but its not used here in this context :D
Thank you in advance

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Upamanyu Roy Choudhury13y ago
Accepted answer
Hi SUNIL,

The SelectedItem property of Combobox is NULL when we do not select any item from the ComboBox, so when we try to write

MessageBox.Show(comboBox1.SelectedItem.ToString());

It will throw an exception.

Therefore you need to put a checking to bypasss this error

private void button1_Click(object sender, EventArgs e)
  {
     if (comboBox1.SelectedIndex != -1)
     {
           MessageBox.Show(comboBox1.SelectedItem.ToString());
      }
  }
  private void Form1_Load(object sender, EventArgs e)
  {
       comboBox1.Items.Add("India");
       comboBox1.Items.Add("Pakistan");
       comboBox1.Items.Add("Bangladesh");
  }

I hope it is now clear to you, please mark this post as an answer if it is of any help
SUNIL GUTTA13y ago
Upamanyu Roy Choudhury

Thank you thank you once again :)

if (comboBox1.SelectedIndex != -1)

It is just perfect :) i also came across it but i ended up at
if (comboBox1.SelectedIndex = -1) :) ha ha

Thank you

and

Satyapriya Nayak Humm when i tried your case problem still do exists :) ty for ur quick reply ty just fallow-up above solution by Upamanyu Roy Choudhury its just perfect :)
Satyapriya Nayak13y ago
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 WindowsFormsApplication7
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (comboBox1.SelectedItem == null)
            {
                MessageBox.Show("Combobox is not Selected.");
            }
            else
            {
                MessageBox.Show(comboBox1.SelectedItem.ToString());
            }
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            comboBox1.Items.Add("a");
            comboBox1.Items.Add("b");
            comboBox1.Items.Add("c");
        }
    }
}