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

See more:

XAML

WPF

combobox

DataGrid

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

class Test: INotifyPropertyChanged
{
    public String Name { get; set; }
    public UserAvailableValue SelectedAvailableValue { get; set; }
    public ObservableCollection<useravailablevalue> AvailableValues { get;  set; }
    public ObservableCollection<string> DefaultValues { get;  set; }
    public String SelectedValue { get; set; }

    public event PropertyChangedEventHandler PropertyChanged;
    private void RaisePropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

public class UserAvailableValue 
{
    public Object Value { get; set; }
    public Object Label { get; set; }
}

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

ObservableCollection<test> UIParams = new ObservableCollection<test>();
// code to fill UIParams collection
dgReportparameters.DataContext = UIParams;

//XAML Code

   <datagrid name="dgReportparameters" itemssource="{Binding}">
               AutoGenerateColumns="False"&gt;
     <datagrid.columns>
     <datagridtextcolumn header="Name" binding="{Binding Name}" />
     <datagridcomboboxcolumn header="Available Values" selecteditembinding="&lt;br" mode="hold" />      "{Binding SelectedAvailableValue, UpdateSourceTrigger=PropertyChanged}" 
       DisplayMemberPath="Label"&gt;
        <datagridcomboboxcolumn.elementstyle>
        &lt;Style TargetType="ComboBox"&gt;
        <setter property="ItemsSource" value="{Binding Path=AvailableValues, &lt;br mode=" hold=" /&gt;         RelativeSource={RelativeSource AncestorType=Window}}" />
         &lt;/Style&gt;
        </datagridcomboboxcolumn.elementstyle>
      
   <datagridtextcolumn header="Default Values" binding="{Binding SelectedValue}" />
   <datagridcheckboxcolumn header="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.