Command is not executing from viewmodel WPF

Click on hyperlink not executing Click() method of Viewmodel through delegate command.

Datacontext is:
DataContext = new DocumentsViewModel();

What I am missing here, please help me.

<TreeView Name="trvMenu" ItemsSource="{Binding ReportPeriods}">
           <TreeView.ItemTemplate>

               <HierarchicalDataTemplate DataType="{x:Type self:dcsReportingPeriod}" ItemsSource="{Binding Path=ChildReports}">
                   <TextBlock Text="{Binding Name}" />
                   <HierarchicalDataTemplate.ItemTemplate>
                       <DataTemplate>
                           <TextBlock>
                               <Hyperlink Command="{Binding ClickCommand}">
                                    <TextBlock Text="{Binding Path=Name}" >
                                       <TextBlock.ContextMenu>
                                           <ContextMenu>
                                               <MenuItem Header ="PDF" ></MenuItem>
                                           </ContextMenu>
                                       </TextBlock.ContextMenu>
                                    </TextBlock>
                               </Hyperlink>
                           </TextBlock>


                       </DataTemplate>
                   </HierarchicalDataTemplate.ItemTemplate>
               </HierarchicalDataTemplate>
           </TreeView.ItemTemplate>
       </TreeView>

public class DocumentsViewModel : NotificationObject
    {
private ObservableCollection<dcsReportingPeriod> _reportPeriods;

        public ObservableCollection<dcsReportingPeriod> ReportPeriods
        {
            get { return _reportPeriods; }
            set
            {
                _reportPeriods = value;
                RaisePropertyChanged("ReportPeriods");
                ClickCommand.RaiseCanExecuteChanged();
            }
        }
 public DelegateCommand ClickCommand { get;  set; }
public DocumentsViewModel()
        {
             ClickCommand = new DelegateCommand(Click, ClickCanExecute);
            ReportPeriods = new ObservableCollection<dcsReportingPeriod>();
            ReportPeriods = null;
}
  public bool ClickCanExecute()
        {
            return ReportPeriods != null;
        }
public void  Click()
        {
            GeodeAssistant.OpenDocument("https://www.google.co.in", true, DocumentNavigationModes.NONE, null, GeodeLaunchModes.Right);
        }
}