Add description and new code example (#3362)

## Pull Request Info - SDK Docs Consolidation

Jira ticket: [DOCSP-34405](https://jira.mongodb.org/browse/DOCSP-34405)
### Staging Links
<!-- start insert-links -->
<li><a
href=https://deploy-preview-3362--device-sdk.netlify.app/sdk/dotnet/react-to-changes/#watch-for-collection-changes>sdk/dotnet/react-to-changes</a></li>
<!-- end insert-links -->

### Release Notes

- **.NET SDK**
  - Add KeyPathsCollection information & code snippet.

.github/pull_request_template.md

@@ -13,6 +13,14 @@ Add links to every SDK's pages where you got the SDK-specific information:
 
 - [PAGE_NAME](https://www.mongodb.com/docs/atlas/device-sdks/LIVE-DOCS-LINK)
 
+### Release Notes
+
+<!--
+- **Define Data Access Permissions**
+  - Data Access Role Examples: Update CRUD Permissions example screenshots and
+    copyable JSON
+-->
+
 ### PR Author Checklist
 
 Before requesting a review for your PR, please check these items:

.github/workflows/netflify-preview-links.yml

@@ -23,7 +23,7 @@ jobs:
             id: build_page_links
             run: |
               new_links=""
-              base_link='https://deploy-preview-${{ github.event.number }}--docs-realm.netlify.app'
+              base_link='https://deploy-preview-${{ github.event.number }}--device-sdk.netlify.app'
               changed_files=${{ steps.changed-files.outputs.all_changed_files }}
               files=$(echo $changed_files | tr "," "\n")
               for file in $files; do

examples/dotnet/Examples/WorkWithRealm.cs

@@ -205,6 +205,33 @@ public void Notifications()
             });
             //:snippet-end:
 
+            NotificationCallbackDelegate<Person> notificationCallback 
+            = new NotificationCallbackDelegate<Person>((sender,changes) => {});
+            //:snippet-start:field-notifications
+            var query = realm.All<Person>();
+            KeyPathsCollection kpc;
+
+            // Use one of these equivalent declarations to 
+            // specify the fields you want to monitor for changes:
+
+            kpc = KeyPathsCollection.Of("Email", "Name");
+            kpc = new List<KeyPath> {"Email", "Name"};
+
+            // To get all notifications for top-level properties
+            // and 4 nested levels of properties, use the `Full` 
+            // static value:
+
+            kpc = KeyPathsCollection.Full;
+
+            // To receive notifications for changes to the
+            // collection only and none of the properties,
+            // use the `Shallow` static value:
+
+            kpc = KeyPathsCollection.Shallow;
+
+            query.SubscribeForNotifications(notificationCallback, kpc);
+            //:snippet-end:
+
             //:snippet-start:unsub-collection-notifications
             // Watch for collection notifications.
             // Call Dispose() when you are done observing the

source/examples/generated/dotnet/WorkWithRealm.snippet.field-notifications.cs

@@ -0,0 +1,22 @@
+var query = realm.All<Person>();
+KeyPathsCollection kpc;
+
+// Use one of these equivalent declarations to 
+// specify the fields you want to monitor for changes:
+
+kpc = KeyPathsCollection.Of("Email", "Name");
+kpc = new List<KeyPath> {"Email", "Name"};
+
+// To get all notifications for top-level properties
+// and 4 nested levels of properties, use the `Full` 
+// static value:
+
+kpc = KeyPathsCollection.Full;
+
+// To receive notifications for changes to the
+// collection only and none of the properties,
+// use the `Shallow` static value:
+
+kpc = KeyPathsCollection.Shallow;
+
+query.SubscribeForNotifications(notificationCallback, kpc);

source/sdk/dotnet/react-to-changes.txt

@@ -93,9 +93,6 @@ notification handler on the collection or handle the `CollectionChanged
 <https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.inotifycollectionchanged.collectionchanged?view=net-6.0>`__ 
 event. 
 
-Register a Collection Change Listener
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
 You can register a notification handler on a specific 
 collection within a realm. The collection can be of realm objects 
 (like ``realm.All<Person>()``) or a collection property on a 
@@ -110,7 +107,10 @@ Realm emits an initial notification when a subscription is added. After the
 initial notification, Realm delivers notifications asynchronously whenever a 
 write transaction adds, modifies, or removes objects in the collection.
 
-Specifically, the notification contains a :dotnet-sdk:`ChangeSet <reference/Realms.ChangeSet.html>` 
+Notification ChangeSets
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The notification contains a :dotnet-sdk:`ChangeSet <reference/Realms.ChangeSet.html>` 
 with 6 properties:
 
 - ``DeletedIndices`` is an ``int[]`` that contains the indices of the objects that were 
@@ -129,6 +129,20 @@ with 6 properties:
   structs that contain the previous and new index of an object moved within the 
   collection.
 
+.. important:: Order Matters
+
+   In collection notification handlers, always apply changes
+   in the following order:
+
+   1. deletions
+   #. insertions
+   #. modifications 
+
+   Handling insertions before deletions may result in unexpected behavior.
+
+Get Notified of All Collection Changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 To subscribe to collection notifications, call the 
 :dotnet-sdk:`SubscribeForNotifications <reference/Realms.CollectionExtensions.html#Realms_CollectionExtensions_SubscribeForNotifications__1_System_Collections_Generic_IDictionary_System_String___0__Realms_NotificationCallbackDelegate_System_Collections_Generic_KeyValuePair_System_String___0___>` 
 method. ``SubscribeForNotifications`` returns a subscription token which can be 
@@ -139,16 +153,17 @@ The following code shows how to observe a collection for changes.
 .. literalinclude:: /examples/generated/dotnet/WorkWithRealm.snippet.collection-notifications.cs
    :language: csharp
 
-.. important:: Order Matters
-
-   In collection notification handlers, always apply changes
-   in the following order:
+Limit Notifications
+~~~~~~~~~~~~~~~~~~~
 
-   1. deletions
-   #. insertions
-   #. modifications 
-
-   Handling insertions before deletions may result in unexpected behavior.
+The SDK provides also provides a 
+:dotnet-sdk:`KeyPathsCollection <reference/Realms.KeyPathsCollection.html>`, which 
+provides a way to filter the fields that will trigger a notification. You pass  
+the ``KeyPathsCollection`` to the ``SubscribeForNotifications`` method. 
+The following code shows how to observe specific fields:
+
+.. literalinclude:: /examples/generated/dotnet/WorkWithRealm.snippet.field-notifications.cs
+   :language: csharp
 
 .. _dotnet-unregister-a-change-listener: