Combobox with textbox inside it in WPF - wpf

Question

I created a combo box that has a text box inside. Now I want it to filter the corresponding items for me when I type in the text box. How can I do this?
<ComboBox Grid.Column="2" Grid.Row="2" Margin="0,10,10,27" Name="comboBox3" >
<TextBox Name="text2" Width="90" TextChanged="text2_TextChanged"
Style="{StaticResource ComboBoxEditableTextBox}"></TextBox>
<ComboBoxItem >salam</ComboBoxItem >
<ComboBoxItem >khobi</ComboBoxItem >
<ComboBoxItem>سلام</ComboBoxItem>
<ComboBoxItem>خوبی</ComboBoxItem>
<ComboBoxItem>عرض ادب</ComboBoxItem>
<ComboBoxItem>سپاسگذارم</ComboBoxItem>
<ComboBoxItem>مرسی</ComboBoxItem>
</ComboBox>
Code:
private void text2_TextChanged(object sender, TextChangedEventArgs e)
{
int c = comboBox3.Items.Count;
MessageBox.Show(c.ToString());
object[] st = new object[c];
List<string> listsource = new List<string>();
for (int i = 1; i <= 8; i++)
{
MessageBox.Show(comboBox3.Items[i].ToString());
// listsource.Add(ComboBox3.Items.IndexOf(ComboBox3.SelectedItem));
// listsource.Add(comboBox3.Items[i].ToString());
// foreach (ComboBoxItem cbi in comboBox3.Items)
}
comboBox2.ItemsSource = listsource;
}

Answer 1

No need to add a TextBox. If you set IsEditable="True" on the ComboBox then you can type a search term directly in the ComboBox.
To filter items handle KeyUp event on the ComboBox. IsDropDownOpen and StaysOpenOnEdit are set to true for testing purpose.
<ComboBox Grid.Column="2" Grid.Row="2" Margin="0,10,10,27" Name="comboBox3"
IsEditable="True" IsDropDownOpen="True" StaysOpenOnEdit="True" KeyUp="comboBox3_KeyUp" >
<ComboBoxItem >salam</ComboBoxItem >
<ComboBoxItem >khobi</ComboBoxItem >
<ComboBoxItem>سلام</ComboBoxItem>
<ComboBoxItem>خوبی</ComboBoxItem>
<ComboBoxItem>عرض ادب</ComboBoxItem>
<ComboBoxItem>سپاسگذارم</ComboBoxItem>
<ComboBoxItem>مرسی</ComboBoxItem>
</ComboBox>
Code behind
private void comboBox3_KeyUp(object sender, KeyEventArgs e)
{
var defaultView = (CollectionView)CollectionViewSource.GetDefaultView(comboBox3.Items);
var searchTerm = comboBox3.Text;
defaultView.Filter = (item) =>
{
var comboBoxItem = (ComboBoxItem)item;
if (string.IsNullOrEmpty(searchTerm) || ((string)comboBoxItem.Content).Contains(searchTerm))
{
return true;
}
else
{
return false;
}
};
defaultView.Refresh();
}