// Get settings of current document
Settings documentSettings = document.Settings;

// Get all categories of current document
Categories groups = documentSettings.Categories;

// Show the number of all the categories to the user
String prompt = "Number of all categories in current Revit document:" + groups.Size;

// get Floor category according to OST_Floors and show its name
Category floorCategory = groups.get_Item(BuiltInCategory.OST_Floors);
prompt += floorCategory.Name;

// Give the user some information
TaskDialog.Show("Revit",prompt);

' Get settings of current document
Dim documentSettings As Settings = document.Settings

' Get all categories of current document
Dim groups As Categories = documentSettings.Categories

' Show the number of all the categories to the user
Dim prompt As [String] = "Number of all categories in current Revit document:" + groups.Size

' get Floor category according to OST_Floors and show its name
Dim floorCategory As Category = groups.Item(BuiltInCategory.OST_Floors)
prompt += floorCategory.Name

' Give the user some information
TaskDialog.Show("Revit", prompt)