Image change when Combobox Selection Changed in WPF

Here is the idea:

You can add to your combo box items of any type. How this type is presented in ComboBox depends on what its method object.ToString returns. You can override this method to return what you need, such as "On"/"Off". Let's take your example.

struct SelectedItemHelper {
    internal SelectedItemHelper(bool value, string text) {
        Text = text; FValue = value;
    } //SelectedItemHelper

    public override string ToString() {
        return Text;
    } //ToString

    internal bool Value {
        get { return FValue; }
        set { FValue = value; }
    } //Value

    string Text;
    bool FValue;
} //SelectedItemHelper

To respond to the change of the item, handle the event SelectionChanged:

ComboBox MyComboBox = new ComboBox();

//...

MyComboBox.Items.Add(new SelectedItemHelper(false, "Off"));
MyComboBox.Items.Add(new SelectedItemHelper(true, "On"));
MyComboBox.SelectedItem = 0; //or 1

MyComboBox.SelectionChanged += (sender, eventArgs) => {
    bool value = ((SelectedItemHelper)((ComboBox)sender).SelectedItem).Value;
    ShowPictire(value); //or whatever you want
}; //MyComboBox.SelectionChanged

This method is very universal and stable: it's easy to support; functionality will not break if you add/delete/modify items (in contrast to case if you access items by index or string). You can add any data to the helper class, whatever you need to support functionality which should respond to item selection. Nearly the same techniques can be used for ListBox and TreeView.

—SA