CODEWITHSUNDEEP
c#winformscomboboxevent-handling
marky
marky

Reputation: 5068

WinForms SelectedIndexChangeCommitted not firing

I'm populating a combobox from a datasource and I have code for when the user changes the selection in the combobox. So obviously I don't want the code in the SelectedIndexChanged method to fire on form load.

This SO question was answered by suggesting two things:

1) Before and after loading the data to the combobox use this code:

private void LoadYourComboBox()
{
    this.comboBox1.SelectedIndexChanged -= new EventHandler(comboBox1_SelectedIndexChanged);
        // Set your bindings here . . .
    this.comboBox1.SelectedIndexChanged += new EventHandler(comboBox1_SelectedIndexChanged);
}

I tried that with this code:

this.cboSelectCategory.SelectedIndexChanged -= new EventHandler(cboSelectCategory_SelectedIndexChanged);

However, the cboSelectCategory_SelectedIndexChanged part has a red error squiggly and hovering over it says: The name cboSelectCategory_SelectedIndexChanged does not exist in the current context. I tried that code in both the form_load and the method that actually populates the combobox.

2) That same SO question had the answer to use the event SelectedIndexChangeCommitted.

private void cboSelectCompany_SelectedIndexChangeCommitted(object sender, EventArgs e)
{
    string selectedCat = cboSelectCategory.SelectedValue.ToString();
    Console.WriteLine(selectedCat);
}

But that event isn't firing when I change the selection in the combobox.

Am I missing something somewhere? Is my code off or in the wrong place?

Upvotes: 0

Views: 87

Answers (1)

Caius Jard
Caius Jard

Reputation: 74730

So obviously I don't want the code in the SelectedIndexChanged method to fire on form load.

If you bind your combobox in the form's constructor (after InitializeComponent()) then SelectedIndexChanged will fire before the form is visible, so you can simply return from the selectedindexchanged event if the form is invisible:

    public MainForm()
    {
        InitializeComponent();

        DataTable dt = new DataTable();
        dt.Columns.Add("Name");
        dt.Columns.Add("Code");


        dt.Rows.Add("Milk", "MLK");
        dt.Rows.Add("Bread", "BRD_WHITE");
        dt.Rows.Add("Bread", "BRD_BROWN");
        dt.Rows.Add("Coffee", "COFF");

        comboBox1.DataSource = dt;
        comboBox1.DisplayMember = "Name";
        comboBox1.ValueMember = "Code";

    }


    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (!this.Visible)
            return;

        MessageBox.Show("a");
    }

It's often easier to simply return from an event handler at an unwanted time than to mess around trying to remove and add event handlers

Side note: If you use a strongly typed dataset and create the bindings using the windows forms designer, the event doesn't fire, I believe because the forms designer InitializeComponent() calls Begin/EndInit on the components at the start and end

Upvotes: 1

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