DOCSP-43911 - Implicit Client-Side Projection in LINQ3 (#242)

source/whats-new.txt

@@ -82,6 +82,77 @@ The 3.0 driver release includes the following new features:
   `TimeOnly Struct. <https://learn.microsoft.com/en-us/dotnet/api/system.timeonly?view=net-6.0>`__
   API reference page on MSDN.
 
+- Adds support for implicit client-side projection when using the ``Find()`` method,
+  the ``Select()`` method, or the ``Project()`` aggregation stage with the LINQ3 provider.
+  In previous versions of the driver, you could perform client-side
+  projection with the LINQ3 provider only after calling the ``ToEnumerable()`` or
+  ``AsEnumerable()`` method.
+
+  To learn how to enable and use client-side projection for a driver method, select the
+  corresponding tab:
+
+  .. tabs::
+
+    .. tab:: Find() Method
+       :tabid: find-method
+
+       .. code-block:: csharp
+
+          // Enable client-side projection
+          var findOptions = new FindOptions();
+          findOptions.TranslationOptions = new ExpressionTranslationOptions
+          {
+              EnableClientSideProjections = true
+          };
+
+          var find = collection
+              .Find(doc => doc.Id == 1, findOptions);
+              .Project(doc => new { R = MyFunction(doc.Name) });
+
+    .. tab:: Select() Method
+       :tabid: select-method
+
+       .. code-block:: csharp
+
+          // Enable client-side projection
+          var aggregateOptions = new AggregateOptions();
+          aggregateOptions.TranslationOptions = new ExpressionTranslationOptions
+          {
+              EnableClientSideProjections = true
+          };
+
+          var queryable = collection
+              .AsQueryable(aggregateOptions)
+              .Where(doc => doc.Id == 1)
+              .Select(doc => new { R = MyFunction(doc.Name) });
+
+    .. tab:: Project() Method
+       :tabid: project-method
+
+       .. code-block:: csharp
+
+          // Enable client-side projection
+          var aggregateOptions = new AggregateOptions();
+          aggregateOptions.TranslationOptions = new ExpressionTranslationOptions
+          {
+              EnableClientSideProjections = true
+          };
+
+          var aggregate = collection
+              .Aggregate(aggregateOptions)
+              .Project(doc => new { R = MyFunction(doc.Name) });
+
+  .. tip:: MongoClientSettings
+
+     To enable client-side projection for all queries on a client, set the
+     ``TranslationOptions`` property of the ``MongoClientSettings`` object to ``true``.
+
+  To learn more about using the aggregation pipeline with the {+driver-short+}, see
+  :ref:`csharp-aggregation`.
+
+For more information about this release, see the :github:`v3.0 release notes
+</mongodb/mongo-csharp-driver/releases/tag/v3.0.0>`.
+
 .. _csharp-version-2.28:
 
 What's New in 2.28