LearnRevitAPI

Oct 30, 2024

👉 Master Selection in Revit API

You need to master Selection if you want to use Revit API🪄.Getting elements is the first step to test your code, so it makes perfect sense to begin with Selection.And it's not so complicated.
Let me teach you the basics in just a few minutes.

Selection Class

Let's begin with the documentation. I know it sounds boring, but coding without docs is like sailing with wind... Not very fun.

There is a Selection Class in Revit API which allows you:

Get user selection
Prompt Selection methods
Set new selection in Revit's UI

Here is the screenshot on Methods:

This class is located in Autodesk.Revit.UI.Selection Namespace.

By exploring this class you will learn about various available methods for selection. And in general they are self-explanatory.

How to use Selection methods?

To use any Selection methods, you first need to get an instance of Selection related to your active project.

Luckily, there is a Selection property in uidoc variable.

Here is how to get it

Now you can use this variable to apply any methods.

💡Importing Selection and making type-hinting with #type:... is optional to get auto-complete.

1. GetElementIds()

Let's begin with the most basic one - GetElementIds

This method returns the ids of the elements that are currently selected within the project.

Here is how to use it:

get selection instance
GetElementIds (current selection)
convert ElementIds to Elements
filter to Walls (optional)

And that's it.

2. PickObjects()

Let's look at the second most used method - PickObjects.

This will prompt user to select elements and confirm the selection before we will get them in the code.

Here is how it works:

get selection instance
import ObjectType (it's necessary as argument)
get References by using PickObjects
convert References to Elements
Check results

💡 Once you start selecting elements in Revit UI, you need to click on Finish in the top left corner to confirm selection.

3. PickElementsByRectangle()

Another way we could prompt selection is to use PickElementsByRectangle method.

This one is very simple, doesn't take any arguments and it returns you a list of Elements, so you don't even need to convert anything.

Here is how it works:

get selection instance
PickElementsByRectangle
that's it

4. SetElementIds()

Lastly, let me show you how to change user selection in Revit UI with the code. It has a lot of use-cases:

Filter Selection
Select elements with warnings
Select elements that match certain criteria
and so on...

Keep in mind that SetElementIds method needs a type list. List[ElementId](), so don't forget to convert your python list to type list if necessary. (let me know if I should write about it too)

In case of FilteredElementCollector this is not necessary, since it already returns a typed list of element Ids.

Here is a simple example to select all walls: