Create a View/Sheet Set

public void CreateSheetSet()
{
    Document doc = this.ActiveUIDocument.Document;

    // create a new ViewSet - add views to it that match the desired criteria
    ViewSet myViewSet = new ViewSet();
    string match = "S";
    foreach (ViewSheet vs in new FilteredElementCollector(doc).OfClass(typeof(ViewSheet)).Cast<ViewSheet>()
             .Where(q => q.SheetNumber.Contains(match)))
    {
        myViewSet.Insert(vs);
    }

    // get the PrintManger from the current document
    PrintManager printManager = doc.PrintManager;

    // set this PrintManager to use the "Selected Views/Sheets" option
    printManager.PrintRange = PrintRange.Select;

    // get the ViewSheetSetting which manages the view/sheet set information of current document
    ViewSheetSetting viewSheetSetting = printManager.ViewSheetSetting;

    // set the views in this ViewSheetSetting to the newly created ViewSet
    viewSheetSetting.CurrentViewSheetSet.Views = myViewSet;

    if (myViewSet.Size == 0)
    {
        TaskDialog.Show("Error", "No sheet numbers contain '" + match + "'.");
        return;
    }

    using (Transaction t = new Transaction(doc,"Create ViewSet"))
    {
        t.Start();
        string setName = "'" + match +"' Sheets";
        try
        {
            // Save the current view sheet set to another view/sheet set with the specified name.
            viewSheetSetting.SaveAs(setName);
        }
        // handle the exception that will occur if there is already a view/sheet set with this name
        catch (Autodesk.Revit.Exceptions.InvalidOperationException)
        {
            TaskDialog.Show("Error", setName + " is already in use");
            t.RollBack();
            return;
        }
        t.Commit();
    }
    TaskDialog.Show("View Set", myViewSet.Size + " sheets added to set");
}