public bool IsEditingEnabled {get;}

// if not editing
if (!Project.Current.IsEditingEnabled)
{
  var res = MessageBox.Show("You must enable editing to use editing tools. Would you like to enable editing?",
                                                        "Enable Editing?", System.Windows.MessageBoxButton.YesNoCancel);
  if (res == System.Windows.MessageBoxResult.No ||
                res == System.Windows.MessageBoxResult.Cancel)
  {
    return;
  }
  Project.Current.SetIsEditingEnabledAsync(true);
}

// if editing
if (Project.Current.IsEditingEnabled)
{
  var res = MessageBox.Show("Do you want to disable editing? Editing tools will be disabled",
                                                         "Disable Editing?", System.Windows.MessageBoxButton.YesNoCancel);
  if (res == System.Windows.MessageBoxResult.No ||
                res == System.Windows.MessageBoxResult.Cancel)
  {
    return;
  }

  //we must check for edits
  if (Project.Current.HasEdits)
  {
    res = MessageBox.Show("Save edits?", "Save Edits?", System.Windows.MessageBoxButton.YesNoCancel);
    if (res == System.Windows.MessageBoxResult.Cancel)
      return;
    else if (res == System.Windows.MessageBoxResult.No)
      Project.Current.DiscardEditsAsync();
    else
    {
      Project.Current.SaveEditsAsync();
    }
  }
  Project.Current.SetIsEditingEnabledAsync(false);
}

// ApplicationOptions.EditingOptions.EnableEditingFromEditTab is true
// ApplicationOptions.EditingOptions.IsSingleWorkspaceEditSession is true

var project = Project.Current;

// check if already editing
if (project.IsEditingEnabled)
{
  // save or discard any edits
  if (project.HasEdits)
  {
    var res = MessageBox.Show("Save edits?", "Save Edits?", System.Windows.MessageBoxButton.YesNoCancel);
    if (res == System.Windows.MessageBoxResult.Cancel)
      return;
    else if (res == System.Windows.MessageBoxResult.No)
      await project.DiscardEditsAsync();
    else
      await project.SaveEditsAsync();
  }
  // close the edit session
  await project.SetIsEditingEnabledAsync(false);
}

// find a layer
var mm = MapView.Active.Map.GetLayersAsFlattenedList().FirstOrDefault(l => l.Name == "Roads");
if (mm == null)
  return;

// start the edit session on the workspace attached to the layer
var success = await project.SetSingleEditWorkspaceAsync(mm);

// if success = true then an edit session was started
// and project.IsEditingEnabled will be true