How to insert item to combobox after binding wpf

Question

Hi All,

I want to add an item to the combobox after binding it. for example:

this.cbCategory.ItemsSource = categoryList;
        this.cbCategory.DisplayMemberPath = "CategoryName";
        this.cbCategory.SelectedValuePath = "CategoryID";

i want to add("All", "%") as the first one.

Geetha.

Answer 1

You'll break the binding if you try to add it later and will no longer receive updates.

Why not just add your 'extra' item before you bind it?

Answer 2

This is very simple using a CompositeCollection:

<ComboBox DisplayMemberPath="CategoryName" SelectedValuePath="CategoryID">
  <ComboBox.ItemsSource>
    <CompositeCollection>
      <my:Item CategoryName="All" CategoryID="%" />
      <CollectionContainer Collection="{Binding CategoryList}" />
    </CompositeCollection>
  </ComboBox.ItemsSource>
</ComboBox>

How it works: The CompositeCollection produes the "All" item followed by all of the items in the CategoryList collection. Note that <my:Item ... /> is the constructor for your item class. You will need to change it to your actual namespace and class name.

Important advice: I notice you are setting some ComboBox properties in code-behind. This is a very bad practice. You should use XAML as shown above.