WinForm: Display BusyForm then run Long Operation on background

Form.cs

    private void compareBtn_Click(object sender, EventArgs e)
    {
      try
      {
        var busyForm = new BusyForm();

        busyForm.Shown += async (sd, args) =>
        {
          try
          {
            //Init GUI before launch
            this.outputEdt.Text = "start"; 

            await Task.Run(() =>
            {
              RunLongOperation();
            });
            
            //Display result to GUI after launch
            this.outputEdt.Text = "finish";
          }
          catch (Exception ex)
          {
            Log.Error(ex);
            errorReporter.Show(ex);
          }
          finally
          {
            busyForm.Close();
          }
        };

        busyForm.ShowDialog(this);
      }
      catch (Exception ex)
      {
        Log.Error(ex);
        errorReporter.Show(ex);
      }
    }