C#

#region workspaces

      public ObservableCollection<WorkspaceViewModel> Workspaces
      {
          get
          {
              if (_workspaces == null)
              {
                  _workspaces = new ObservableCollection<WorkspaceViewModel>();
                  _workspaces.CollectionChanged += OnWorkspacesChanged;
              }
              return _workspaces;
          }
      }

      private void OnWorkspacesChanged(object sender, NotifyCollectionChangedEventArgs e)
      {
          if (e.NewItems != null && e.NewItems.Count != 0)
              foreach (WorkspaceViewModel workspace in e.NewItems)
                  workspace.RequestClose += OnWorkspaceRequestClose;

          if (e.OldItems != null && e.OldItems.Count != 0)
              foreach (WorkspaceViewModel workspace in e.OldItems)
                  workspace.RequestClose -= OnWorkspaceRequestClose;
      }

      private void OnWorkspaceRequestClose(Object sender, EventArgs e)
      {
          var workspace = sender as WorkspaceViewModel;
          if (workspace != null)
          {
              workspace.Dispose();
              Workspaces.Remove(workspace);
          }
      }

      #endregion

      #region private helpers

      private void DisplayAllFoo()
      {
          var workspace =
              Workspaces.FirstOrDefault(vm => vm is AllFooViewModel)
              as AllFooViewModel;

          if (workspace == null)
          {
              workspace = new AllFooViewModel();
              Workspaces.Add(workspace);
          }

          SetActiveWorkspace(workspace);
      }

      private static void DisplayFoo()
      {
      }

      public void SetActiveWorkspace(WorkspaceViewModel workspace)
      {
          Debug.Assert(Workspaces.Contains(workspace));

          var collectionView = CollectionViewSource.GetDefaultView(Workspaces);
          if (collectionView != null)
              collectionView.MoveCurrentTo(workspace);
      }

      #endregion

ActiveDB.DBContractsClient _Proxy = new ActiveDB.DBContractsClient();
            
            _Proxy.Open();

            _Proxy.ExecuteQuery("Select 1", new object[] { });

            _Proxy.Close();

            _Proxy.Open();
          _Proxy.Close();