Combobox with static and dynamic data together in wpf - wpf

Question

As the title suggests I want to add a static Item to a dataBound ComboBox.
I have refered this post.
Databinding a Combobox :
<ComboBox Name="comboBox1" Width="Auto" ItemsSource="{Binding}" />
Adding Static Items to a combobox :
<ComboBox Text="Is not open">
<ComboBoxItem Name="cbi1">Item1</ComboBoxItem>
<ComboBoxItem Name="cbi2">Item2</ComboBoxItem>
<ComboBoxItem Name="cbi3">Item3</ComboBoxItem>
</ComboBox>
Doing the above things together using CompositeCollection :
<ComboBox>
<ComboBox.Items>
<CompositeCollection>
<CollectionContainer Collection="{Binding Source={...whatever...}" />
<ComboBoxItem Name="cbi1">Item1</ComboBoxItem>
<ComboBoxItem Name="cbi2">Item2</ComboBoxItem>
<ComboBoxItem Name="cbi3">Item3</ComboBoxItem>
</CompositeCollection>
</ComboBox.Items>
</ComboBox>
But the above examples does not solve my problem.
I want to add a static Item to a dataBound ComboBox in which I use DataTemplate
Here is my Code for dataBound ComboBox (I don't know how to add static Items):
<ComboBox x:Name="cbUnder" ItemsSource="{Binding GroupsAndCorrespondingEffects}"
IsEditable="True" SelectedItem="{Binding SelectedGroup, Mode=TwoWay}"
TextSearch.TextPath="GroupName" Grid.Column="1" Grid.ColumnSpan="4" Grid.Row="3">
<ComboBox.ItemTemplate>
<DataTemplate>
<VirtualizingStackPanel Orientation="Horizontal">
<TextBlock Text="{Binding GroupName}" Width="250"/>
<TextBlock Text="{Binding CorrespondingEffect}" />
</VirtualizingStackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
Update as requested by aks81 :
Here is the code for GroupsAndCorrespondingEffects
public GroupsViewModel()
{
using (DBEntities db = new DBEntities())
{
GroupsAndCorrespondingEffects = (from g in db.Groups
select new GroupAndCorrespondingEffect
{
GroupName = g.Name,
CorrespondingEffect = g.Type_Effect.Name
}
).ToList().OrderBy(g => g.GroupName);
Items = (from e in db.Type_Effect
select e.Name).ToList();
}
}
public static GroupsViewModel CurrentInstance { get { return Instance; } }
private IEnumerable<GroupAndCorrespondingEffect> _groupsAndCorrespondingEffects;
public IEnumerable<GroupAndCorrespondingEffect> GroupsAndCorrespondingEffects
{
get
{
return _groupsAndCorrespondingEffects;
}
set
{
_groupsAndCorrespondingEffects = value;
OnPropertyChanged("GroupsAndCorrespondingEffects");
}
}

Answer 1

Check out this link and let me know if it was useful :)
http://social.msdn.microsoft.com/Forums/vstudio/en-US/86229c53-15bd-4780-bee3-c6c2cdae81e7/select-multiple-checkboxes-placed-inside-a-combobox
have a nice day!