04 - Step-by-Step: Parameter Engine and the Params class

Practice transforming C# properties into interactive UI elements.

1. Create a Params Class

1. Open a script in VS Code.
2. At the bottom of the file (outside other classes), add:

   public class Params {
       public double OffsetDistance { get; set; } = 12.0;
   }

3. Save (Ctrl+S) and return to the Parameters tab in Paracore.

2. Add Revit Types (Single & Lists)

1. In VS Code, add these properties to your Params class:

   public WallType TargetType { get; set; }
   public List<WallType> AllTypes { get; set; }

2. Save and observe the new UI fields.
3. Click the Compute button next to these parameters to populate them from your Revit model.

3. Advanced Filtering ([RevitElements])

1. Add a filtered property:

   [RevitElements(Category = "Doors")]
   public FamilySymbol? DoorType { get; set; }

2. Save, click Compute, and verify that only Door Symbols appear.

4. Custom Providers (_Options and _Filter)

1. Add a curated list property and its provider:

   public List<Wall> GenericWalls { get; set; }
   public List<Wall> GenericWalls_Options => 
       new FilteredElementCollector(Doc).OfClass(typeof(Wall)).Cast<Wall>()
       .Where(w => w.Name.Contains("Generic")).ToList();

2. Add a filtered list property and its predicate:

   public List<Room> LargeRooms { get; set; }
   public bool LargeRooms_Filter(Room r) => r.Area > 20.0;

3. Save, click Compute, and observe the filtered lists.

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Next Exercise: 05 - Parameter Defaults and Cache