DOCSP-46303 Update replace documents (#406)

(cherry picked from commit a9ad799)

Author: stephmarie17

source/fundamentals/crud/write-operations/replace.txt

@@ -109,8 +109,26 @@ corresponding code.
 
 .. important::
 
-   The values of ``_id`` fields are immutable. If your replacement document specifies 
-   a value for the ``_id`` field, it must match the ``_id`` value of the existing document.
+   The values of ``_id`` fields are immutable. If your replacement document
+   specifies a value for the ``_id`` field, it must match the ``_id`` value of
+   the existing document. 
+   
+   If your replacement document does not specify a value for the ``_id`` field,
+   you can add the ``[BsonIgnoreIfDefault]`` attribute to the ``_id`` field in
+   your Plain Old CLR/Class Object (POCO). Use ``[BsonIgnoreIfDefault]`` if the
+   ``_id`` field in your POCO is of the ``ObjectId`` type.
+   
+   The following example shows how to add this attribute:
+
+   .. code-block:: csharp
+
+      public class Restaurant
+      {
+          [BsonIgnoreIfDefault]
+          public ObjectId Id { get; set; }
+
+          // Other properties
+      }
 
 Customize the Replace Operation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

source/includes/code-examples/replace-one/ReplaceOne.cs

@@ -49,9 +49,14 @@ private static ReplaceOneResult ReplaceOneRestaurant()
         var filter = Builders<Restaurant>.Filter
             .Eq(r => r.Cuisine, "Pizza");
 
+        // Finds the ID of the first restaurant document that matches the filter
+        var oldPizzaRestaurant = _restaurantsCollection.Find(filter).First();
+        var oldId = oldPizzaRestaurant.Id;
+
         // Generates a new restaurant document
         Restaurant newPizzaRestaurant = new()
         {
+            Id = oldId
             Name = "Mongo's Pizza",
             Cuisine = "Pizza",
             Address = new Address()
@@ -73,9 +78,14 @@ private static ReplaceOneResult ReplaceOneRestaurantWithOptions()
         var filter = Builders<Restaurant>.Filter
             .Eq(r => r.Cuisine, "Pizza");
 
+        // Finds the ID of the first restaurant document that matches the filter
+        var oldPizzaRestaurant = _restaurantsCollection.Find(filter).First();
+        var oldId = oldPizzaRestaurant.Id;
+
         // Generates a new restaurant document
         Restaurant newPizzaRestaurant = new()
         {
+            Id = oldId
             Name = "Mongo's Pizza",
             Cuisine = "Pizza",
             Address = new Address()

source/includes/code-examples/replace-one/ReplaceOneAsync.cs

@@ -48,10 +48,15 @@ private static async Task<ReplaceOneResult> ReplaceOneRestaurantAsync()
         // start-replace-one-async
         var filter = Builders<Restaurant>.Filter
             .Eq(r => r.Cuisine, "Pizza");
+        
+        // Finds the ID of the first restaurant document that matches the filter
+        var oldPizzaRestaurant = _restaurantsCollection.Find(filter).First();
+        var oldId = oldPizzaRestaurant.Id;
 
         // Generates a new restaurant document
         Restaurant newPizzaRestaurant = new()
-        {
+        {   
+            Id = oldId
             Name = "Mongo's Pizza",
             Cuisine = "Pizza",
             Address = new Address()
@@ -72,9 +77,14 @@ private static async Task<ReplaceOneResult> ReplaceOneRestaurantAsyncWithOptions
         var filter = Builders<Restaurant>.Filter
             .Eq(r => r.Cuisine, "Pizza");
 
+        // Finds the ID of the first restaurant document that matches the filter
+        var oldPizzaRestaurant = _restaurantsCollection.Find(filter).First();
+        var oldId = oldPizzaRestaurant.Id;
+
         // Generates a new restaurant document
         Restaurant newPizzaRestaurant = new()
         {
+            Id = oldId
             Name = "Mongo's Pizza",
             Cuisine = "Pizza",
             Address = new Address()