revit-element-collector

name	revit-element-collector
description	Query the Revit model with the Nice3point.Revit.Extensions fluent FilteredElementCollector wrappers; filter with Revit's parameter filters, not by loading elements and filtering with LINQ. USE FOR: writing or reviewing element queries that filter by class, category, or parameter value and return the first match, a count, or the full set. DO NOT USE FOR: reading or setting parameters on an element you already hold (use revit-element-and-parameter-access).
license	MIT

Revit Element Collector

Query the model through the fluent FilteredElementCollector wrappers in Nice3point.Revit.Extensions. They wrap the raw Revit collector API into a single readable chain and keep filtering inside Revit's native database engine, which evaluates filters before elements expand into memory. Filtering the collector output with LINQ materializes every element first.

When to use

• Retrieving elements, types, or instances by class, category, or parameter value.
• Reviewing code that writes new FilteredElementCollector(document) by hand or filters collector output with .Where(...).
• Fetching just the first match or a count without loading the whole result set.

When not to use

• You already hold the element and only need to read or set its parameters — use revit-element-and-parameter-access.
• You need a specialized ElementFilter the extensions do not expose — fall back to a raw FilteredElementCollector with that filter.

Workflow

Always prefer the built-in methods of FilteredElementCollector extensions over using LINQ. LINQ materializes and marshals every element into the .NET process's memory and does not filter at the database level; use it only if the built-in methods are insufficient for filtering.

Step 1: Open a collector from the document

var collector = document.CollectElements(); // whole document
var viewScoped = document.CollectElements(view); // elements visible in a view
var restricted = document.CollectElements(elementIds); // a known id set

Step 2: Apply quick filters as generic, typed calls

Prefer the generic and multi-argument overloads over raw typeof filters.

var walls = document.CollectElements()
    .OfClass<Wall>()
    .ToElements();

var openings = document.CollectElements()
    .OfCategories(BuiltInCategory.OST_Walls, BuiltInCategory.OST_Floors)
    .Instances() // only instances; use .Types() for element types
    .ToElements();

Step 3: Filter by parameter with native rules, not LINQ

WhereParameter builds a native ElementParameterFilter — evaluated at the database level before element expansion — then continues the collector chain.

var tallWalls = document.CollectElements()
    .OfClass<Wall>()
    .WhereParameter(BuiltInParameter.WALL_USER_HEIGHT_PARAM).IsGreaterThan(3.0, 1e-6)
    .ToElements();

// BAD — loads every wall into memory, then filters
var tallWalls = new FilteredElementCollector(document)
    .OfClass(typeof(Wall))
    .Cast<Wall>()
    .Where(wall => wall.get_Parameter(BuiltInParameter.WALL_USER_HEIGHT_PARAM).AsDouble() > 3.0);

Comparisons include Equals, IsGreaterThan/IsGreaterThanOrEqualTo, IsLessThan/IsLessThanOrEqualTo (with an optional double epsilon), Contains/StartsWith (and their Not… inversions), and HasValue.

Step 4: Terminate with the fast native path

Use the extension terminators, not LINQ; they call Revit's native fast implementations (Count() uses the fast GetElementCount() implementation).

var firstRoom = document.CollectElements().OfClass<SpatialElement>().FirstOrDefault();
var wallCount = document.CollectElements().OfClass<Wall>().Count();
var hasLevels = document.CollectElements().OfClass<Level>().Any();

Step 5: Verify

1. The query builds the filter through collector methods, not .Where(...) over materialized elements.
2. A parameter comparison uses WhereParameter, not a post-collection predicate.
3. The terminator is a native call (ToElements, First, FirstOrDefault, Count, Any).

Validation

• The collector comes from document.CollectElements(...), not a hand-written new FilteredElementCollector(...).
• Class and category filters use the generic/multi-argument extensions.
• Parameter conditions use WhereParameter(...), filtering at the database level.
• Single-result and count queries use First/FirstOrDefault/Count/Any, not LINQ.
• A quick filter (class/category) precedes a slow filter (parameter) to shrink the candidate set.

Common Pitfalls

Pitfall	Correct approach
.Where(element => element.get_Parameter(...).AsDouble() > x) after the collector	WhereParameter(param).IsGreaterThan(x, epsilon) — a native rule.
collector.ToElements().Count / .Any() (LINQ over the list)	collector.Count() / collector.Any() — native fast paths.
Comparing double parameters without an epsilon	Use the IsGreaterThan(value, epsilon) overload.
CollectElements or WhereParameter not found	The Nice3point.Revit.Extensions package is not referenced in the project.
Reusing one collector after a terminator	Start a fresh CollectElements() per query; terminators stop the iterator.