Comobo Box selected index problem

I am assuming that you are setting the selected index of the combo box so that it matches some default value, e.g. editing some sort of record.

The easiest way is to remove the event handler before the change and add if back afterwards.

Assuming that the combobox is called comboBox1 and that the event handler is called comboBox1_SelectedIndexChanged then this should do the job.

using System.Collections.Generic;
using System.Windows.Forms;

namespace sample
{
    public partial class Form1 : Form
    {

        // possible values
        private List<string> _items = new List<string>() { "One", "Two" };

        public Form1()
        {
            InitializeComponent();

            DataBind();
        }

        private void DataBind()
        {
            // disable event handler
            comboBox1.SelectedIndexChanged -= this.comboBox1_SelectedIndexChanged;

            // bind possible values
            comboBox1.DataSource = _items;

            //your logic to get this number
            int selectedIndex = 1;

            //set default value - 
            comboBox1.SelectedIndex = selectedIndex;

            // enable event handler
            comboBox1.SelectedIndexChanged += this.comboBox1_SelectedIndexChanged;
        }

        private void comboBox1_SelectedIndexChanged(object sender, System.EventArgs e)
        {
            // normal logic to handle selection chnage
            MessageBox.Show("fired");
        }
    }
}</string></string>

When I need to do that, I create a variable called m_initialized, and set it to an initial value of false. At the end of the Load event handler, I set it to true. Then in the SelectionChanged event handler for the control, I check to see if m_initialized is true, and if so, I handle the event. Otherwise, I exit the handler.

I run into this when I am setting up a form in the Form Load event. I work around it by declaring a form level variable and checking in right away in the combo box SelectedIndexChange event to decide if I will perform the code in the event or not. so like this: (It's in vb but you should get the idea)

Private boolPastLoad As Boolean = False

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    'Add code here to setup the form
    ComboBox1.SelectedIndex = 0

    boolPastLoad = True
End Sub

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
    If boolPastLoad Then
        'Add code here for whatever should usually happen on the SelectedIndexChanged
    End If

End Sub

set AutoPostback="false" in aspx page in dropdown control