Tutorial 4: Element Selection

Learn how to let the user "Pick" elements from the model, using Paracore's Strongly Typed Selection to safely get exactly what you need.

Finished Script: 03_Tutorials/Paracore_Fundamentals/04_ElementSelection.cs

What You'll Learn

• The [Select] attribute
• Strongly Typed Selection: Asking for a Wall instead of a generic ID
• Modifying element parameters

Step 1: Define Inputs (The Smart Way)

In the past, you had to ask for a generic Reference or long (Element ID) and then manually find the object. With Paracore Hydration, you just ask for the type you want.

public class Params
{
    /// <summary>Select a Wall in Revit</summary>
    [Select(SelectionType.Element)]
    [Mandatory]
    public Wall TargetWall { get; set; }
    
    /// <summary>New comment text</summary>
    public string Comment { get; set; } = "Updated by Paracore";
}

Notice public Wall TargetWall. Paracore sees this and:

1. Gives the user a "Pick" button.
2. Filters the selection so they can only pick a wall.
3. Returns the actual Wall object to your script.

Step 2: Validate the Selection

Even though Paracore filters selection, the user might cancel or something might go wrong. Always check for null.

var p = new Params();

if (p.TargetWall == null)
{
    Println("No wall selected.");
    return;
}

Note: We don't need Doc.GetElement(id). We already have p.TargetWall!

Step 3: Modify the Element

Let's update the comments on the selected wall.

Transact("Update Wall Comment", () => {
    // Modify the real Wall object directly
    var param = p.TargetWall.get_Parameter(BuiltInParameter.ALL_MODEL_INSTANCE_COMMENTS);
    param?.Set(p.Comment);
    
    Println($"Updated Wall {p.TargetWall.Id} with comment: {p.Comment}");
});

Step 4: Run and Verify

1. Click the "Pick" button next to TargetWall.
2. The Paracore window will minimize.
3. Try to pick a Floor or Window -> Revit won't let you!
4. Pick a Wall.
5. Enter a comment and click Run Script.
6. Select the wall in Revit and check its properties.

Try This

1. Change public Wall to public Window and see how the selection filter changes.
2. Use [Select(SelectionType.Point)] with public XYZ Point to pick a location in 3D space.

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Next: Tutorial 5: Modular Projects ->