how to bind custom class collections to wpf datagrid combobox (multiselected)

Please help me figure out how to bind custom class collection to datagrid combobox. My custom class is

classTest:INotifyPropertyChanged{publicStringName{get;set;}publicUserAvailableValueSelectedAvailableValue{get;set;}publicObservableCollection<UserAvailableValue>AvailableValues{get;set;}publicObservableCollection<String>DefaultValues{get;set;}publicStringSelectedValue{get;set;}publiceventPropertyChangedEventHandlerPropertyChanged;privatevoidRaisePropertyChanged(string propertyName){if(this.PropertyChanged!=null)this.PropertyChanged(this,newPropertyChangedEventArgs(propertyName));}}publicclassUserAvailableValue{publicObjectValue{get;set;}publicObjectLabel{get;set;}}

From code behind, i am setting DataGrid Datacontext i.g.

ObservableCollection<Test>UIParams=newObservableCollection<Test>();// code to fill UIParams collection
   dgReportparameters.DataContext=UIParams;//XAML Code<DataGridName="dgReportparameters"ItemsSource="{Binding}"AutoGenerateColumns="False"><DataGrid.Columns><DataGridTextColumnHeader="Name"Binding="{Binding Name}"/><DataGridComboBoxColumnHeader="Available Values"SelectedItemBinding="{Binding SelectedAvailableValue, UpdateSourceTrigger=PropertyChanged}"DisplayMemberPath="Label"><DataGridComboBoxColumn.ElementStyle><StyleTargetType="ComboBox"><SetterProperty="ItemsSource"Value="{Binding Path=AvailableValues,
         RelativeSource={RelativeSource AncestorType=Window}}"/></Style></DataGridComboBoxColumn.ElementStyle></DataGridComboBoxColumn><DataGridTextColumnHeader="Default Values"Binding="{Binding SelectedValue}"/><DataGridCheckBoxColumnHeader="Nullable"Binding="{Binding IsNullable}"/></DataGrid.Columns></DataGrid>

Except DataGridComboBoxColumn other columns are showing correct values.DataGridComboBoxColumn is showing blank column. UIParams collection has multiple parameters while each parameter has name and Available values and one default value. I want to show paramters in datagrid and let user select one/multiple values from Available column combobox. Each parameter has its own set of available values. Most of the example i found have Common collection in dropdown but in my case each row of datagrid has different available values.

Please help me to have combobox in datagrid.

Thanks in advance.