Passing checkedlistbox.checked items cast as a List<BuiltInCategory> from a Form instance to a Revit class function - winforms

Question

I am not having any issues making calls from the form instance to the Revit class. It's when I try to assign a List to the Revit class's function categoryList(), that I get a variable doesn't exist in the context error. I tried prefixing a reference to the instance of the form class "Form UF = new Form;" This doesn't work.
//The Revit Class
public Result Execute(ExternalCommandData commandData, ref string message,....)
{
User_Form UF = new User_Form(commandData);
UF.ShowDialog();
public List<BuiltInCategory> categoryList(Document doc, int intSwitch)
{
//list built in categories for built in filter_1
builtInCats_List = new List<BuiltInCategory>();
switch (intSwitch)
{
case (1):
...
case (3):
...
case (4):
{
builtInCats_List = newStateCb1;
return builtInCats_List;
}
default:
{
builtInCats_List = newStateCb1;
return builtInCats_List;
}
}
}
using Form = System.Windows.Forms.Form;
using WS = ModelAuditor_2014.WorksetSorter_2014;
using ModelAuditor_2014;
using System.Threading;
//The Form
namespace ModelAuditor_2014
{
public partial class User_Form : Form
{
//Constructor
WorksetSorter_2014 WS = new WorksetSorter_2014();
//Revit references
public Autodesk.Revit.UI.UIApplication rvtUiApp;
public Autodesk.Revit.UI.UIDocument rvtUiDoc;
public Autodesk.Revit.ApplicationServices.Application rvtApp;
//Global Variables
public List<BuiltInCategory> Filter01_CategoryList;
public List<BuiltInCategory> Filter02_CategoryList;
public int intSwitch;
public List<BuiltInCategory> newStateCb1;
public User_Form(ExternalCommandData commandData)
{
//Revit references
rvtUiApp = commandData.Application;
rvtUiDoc = rvtUiApp.ActiveUIDocument;
rvtApp = rvtUiApp.Application;
InitializeComponent();
}
public void User_Form_Load(object sender, EventArgs e)
{
//use rvtDoc = Doc
Autodesk.Revit.DB.Document rvtDoc = .....
//CheckedListBox for filter01
checkedListBox1.DataSource = WS.categoryList(rvtDoc, intSwitch = 1);
Filter01_CategoryList = new List<BuiltInCategory>();
Filter01_CategoryList = WS.RetrieveSchema(rvtDoc, false);
foreach (BuiltInCategory ChkedB1 in Filter01_CategoryList)
{
for (int i = 0; i < checkedListBox1.Items.Count; i++)
{
if (checkedListBox1.Items[i].ToString() == ChkedB1.ToString())
{
checkedListBox1.SetItemChecked(i, true);
}
}
}
public List<BuiltInCategory> returnNewStateCB1()
{
newStateCb1 = checkedListBox1.CheckedItems.Cast
<BuiltInCategory>().ToList<BuiltInCategory>();
return newStateCb1;
}

Answer 1

I passed the list from the win form to another public function in the revit app, I was able to access the list returned by this function.