DOCSP-42611: Filter Inject() example (#375)

Author: mcmorisi

Diff for: source/fundamentals/builders.txt

@@ -89,6 +89,16 @@ Alternatively, you can use string-based field names to contruct the filter:
    var builder = Builders<Flower>.Filter;
    var filter = builder.Lt("Price", 20) & builder.Eq("Category", "Perennial");
 
+If you are using LINQ, you can also use the ``Inject()`` method to apply the filter
+to a LINQ query:
+
+.. code-block:: csharp
+   :copyable: true
+
+   var builder = Builders<Flower>.Filter;
+   var filter = builder.Lt("Price", 20) & builder.Eq("Category", "Perennial");
+   var query = collection.AsQueryable().Where(f => filter.Inject());
+
 Array Operators
 ~~~~~~~~~~~~~~~