V3.0-backports (mongodb#378)

* DOCSP-35829-new-districtmany-method (mongodb#367)

(cherry picked from commit 65e9142)

* DOCSP-40654-sample-aggregation-operator (mongodb#360)

* DOCSP-40654-sample-aggregation-operator

* changed some syntax

* update code example

(cherry picked from commit 6d0a1e9)

Author: gmiller-mdb

source/fundamentals/linq.txt

@@ -249,6 +249,32 @@ The result of the preceding example contains the following documents:
     { "name" : "Crystal Room", "cuisine" : "Italian" }
     { "name" : "Forlinis Restaurant", "cuisine" : "Italian" }
 
+$sample
+~~~~~~~
+
+The ``$sample`` aggregation stage returns a random sample of documents from a 
+collection. The following example shows how to generate a ``$sample`` stage by using
+LINQ: 
+
+.. code-block:: csharp
+   :emphasize-lines: 4
+
+   var query = queryableCollection
+       .Aggregate()
+       .Sample(4)
+       .ToList();
+
+The result of the preceding example contains the following documents:
+
+.. code-block:: json
+
+   // Results Truncated
+
+   { "name" : "Von Dolhens", "cuisine" : "Ice Cream, Gelato, Yogurt, Ices" }
+   { "name" : "New York Mercantile Exchange", "cuisine" : "American" }
+   { "name" : "Michaelangelo's Restaurant", "cuisine" : "Italian" }
+   { "name" : "Charlie Palmer Steak", "cuisine" : "American" }
+
 $skip
 ~~~~~
 
@@ -809,6 +835,12 @@ The following are some methods supported by the {+driver-long+} implementation o
    * - ``Exists``
      - Tests whether a field exists
 
+   * - ``DistinctMany``
+     - Returns distinct documents from an array that match the specified criteria
+
+   * - ``Exists``
+     - Tests whether a field exists
+
    * - ``First``
      - Returns the first matching document, and throws an exception if none are found