Question

I want to make a ComboBox where the user can type an integer value into the text area, but the drop-down list contains several “defaults” values. For instance, the items in the drop-down list would be formatted like this:

• Default – 0
• Value 1 – 1
• Value 2 – 2

What I want is that when the user selects an item (e.g. “Default – 0”), the ComboBox text will display only the number “0” rather than “Default – 0”. The word “Default” is just informational text.

I have played with the following events: SelectedIndexChanged, SelectedValueChanged, and SelectionChangeCommitted, but I was not able to change the text of the ComboBox.

private void ModificationCombobox_SelectionChangeCommitted(object sender, EventArgs e)
{
     ComboBox comboBox = (ComboBox)sender; // That cast must not fail.
     if (comboBox.SelectedIndex != -1)
     {
        comboBox.Text = this.values[comboBox.SelectedItem.ToString()].ToString(); // Text is not updated after...
     }
 }

Answer 1

You can define a class for your ComboBox item, then create a List<ComboBoxItem> and use it as your Combobox.DataSource. With this you can set ComboBox.DisplayMember to a property you want displaying and still get reference to your object from ComboBox_SelectedIndexChanged():

class ComboboxItem
{
  public int Value { get; set; }
  public string Description { get; set; }
}

public partial class Form1 : Form
{
  List<ComboboxItem> ComboBoxItems = new List<ComboboxItem>();
  public Form1()
  {
    InitializeComponent();
    ComboBoxItems.Add(new ComboboxItem() { Description = "Default = 0", Value = 0 });
    ComboBoxItems.Add(new ComboboxItem() { Description = "Value 1 = 1", Value = 1 });
    ComboBoxItems.Add(new ComboboxItem() { Description = "Value 2 = 2", Value = 2 });
    comboBox1.DataSource = ComboBoxItems;
    comboBox1.DisplayMember = "Value";

  }

  private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
  {
    var item = (ComboboxItem)((ComboBox)sender).SelectedItem;
    var test = string.Format("Description is \'{0}\', Value is  \'{1}\'", item.Description, item.Value.ToString());
    MessageBox.Show(test);
  }
}

[edit]
If you want to change displayed text when box toogles between DropDown states try this: (this is a concept, not sure how that would behave)

    private void comboBox1_DropDown(object sender, EventArgs e)
    {
        comboBox1.DisplayMember = "Description";
    }

    private void comboBox1_DropDownClosed(object sender, EventArgs e)
    {
        comboBox1.DisplayMember = "Value";
    }