update references to 8.x code

Author: timdeschryver

aspnetcore/tutorials/first-mongo-app/includes/first-mongo-app8.md

@@ -175,7 +175,7 @@ Use the previously installed MongoDB Shell in the following steps to create a da
 1. Add a *Models* directory to the project root.
 1. Add a `Book` class to the *Models* directory with the following code:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples_snapshot/6.x/Book.cs":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples_snapshot/8.x/Book.cs":::
 
    In the preceding class, the `Id` property is:
 
@@ -189,48 +189,48 @@ Use the previously installed MongoDB Shell in the following steps to create a da
 
 1. Add the following database configuration values to `appsettings.json`:
 
-   :::code language="json" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/appsettings.json" highlight="2-6":::
+   :::code language="json" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/appsettings.json" highlight="2-6":::
 
 1. Add a `BookStoreDatabaseSettings` class to the *Models* directory with the following code:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Models/BookStoreDatabaseSettings.cs":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Models/BookStoreDatabaseSettings.cs":::
 
    The preceding `BookStoreDatabaseSettings` class is used to store the `appsettings.json` file's `BookStoreDatabase` property values. The JSON and C# property names are named identically to ease the mapping process.
 
 1. Add the following highlighted code to `Program.cs`:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Program.cs" id="snippet_BookStoreDatabaseSettings" highlight="4-5":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Program.cs" id="snippet_BookStoreDatabaseSettings" highlight="4-5":::
 
    In the preceding code, the configuration instance to which the `appsettings.json` file's `BookStoreDatabase` section binds is registered in the Dependency Injection (DI) container. For example, the `BookStoreDatabaseSettings` object's `ConnectionString` property is populated with the `BookStoreDatabase:ConnectionString` property in `appsettings.json`.
 
 1. Add the following code to the top of `Program.cs` to resolve the `BookStoreDatabaseSettings` reference:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Program.cs" id="snippet_UsingModels":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Program.cs" id="snippet_UsingModels":::
 
 ## Add a CRUD operations service
 
 1. Add a *Services* directory to the project root.
 1. Add a `BooksService` class to the *Services* directory with the following code:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Services/BooksService.cs" id="snippet_File":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Services/BooksService.cs" id="snippet_File":::
 
    In the preceding code, a `BookStoreDatabaseSettings` instance is retrieved from DI via constructor injection. This technique provides access to the `appsettings.json` configuration values that were added in the [Add a configuration model](#add-a-configuration-model) section.
 
 1. Add the following highlighted code to `Program.cs`:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Program.cs" id="snippet_BooksService" highlight="7":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Program.cs" id="snippet_BooksService" highlight="7":::
 
    In the preceding code, the `BooksService` class is registered with DI to support constructor injection in consuming classes. The singleton service lifetime is most appropriate because `BooksService` takes a direct dependency on `MongoClient`. Per the official [Mongo Client reuse guidelines](https://mongodb.github.io/mongo-csharp-driver/2.14/reference/driver/connecting/#re-use), `MongoClient` should be registered in DI with a singleton service lifetime.
 
 1. Add the following code to the top of `Program.cs` to resolve the `BooksService` reference:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Program.cs" id="snippet_UsingServices":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Program.cs" id="snippet_UsingServices":::
 
 The `BooksService` class uses the following `MongoDB.Driver` members to run CRUD operations against the database:
 
 * [MongoClient](https://mongodb.github.io/mongo-csharp-driver/2.14/apidocs/html/T_MongoDB_Driver_MongoClient.htm): Reads the server instance for running database operations. The constructor of this class is provided in the MongoDB connection string:
 
-  :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Services/BooksService.cs" id="snippet_ctor" highlight="4-5":::
+  :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Services/BooksService.cs" id="snippet_ctor" highlight="4-5":::
 
 * [IMongoDatabase](https://mongodb.github.io/mongo-csharp-driver/2.14/apidocs/html/T_MongoDB_Driver_IMongoDatabase.htm): Represents the Mongo database for running operations. This tutorial uses the generic [GetCollection\<TDocument>(collection)](https://mongodb.github.io/mongo-csharp-driver/2.14/apidocs/html/M_MongoDB_Driver_IMongoDatabase_GetCollection__1.htm) method on the interface to gain access to data in a specific collection. Run CRUD operations against the collection after this method is called. In the `GetCollection<TDocument>(collection)` method call:
 
@@ -248,7 +248,7 @@ The `BooksService` class uses the following `MongoDB.Driver` members to run CRUD
 
 Add a `BooksController` class to the *Controllers* directory with the following code:
 
-:::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Controllers/BooksController.cs":::
+:::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Controllers/BooksController.cs":::
 
 The preceding web API controller:
 
@@ -304,19 +304,19 @@ To satisfy the preceding requirements, make the following changes:
 
 1. In `Program.cs`, chain the following highlighted code on to the `AddControllers` method call:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Program.cs" id="snippet_AddControllers" highlight="10-11":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Program.cs" id="snippet_AddControllers" highlight="10-11":::
 
    With the preceding change, property names in the web API's serialized JSON response match their corresponding property names in the CLR object type. For example, the `Book` class's `Author` property serializes as `Author` instead of `author`.
 
 1. In `Models/Book.cs`, annotate the `BookName` property with the [`[JsonPropertyName]`](xref:System.Text.Json.Serialization.JsonPropertyNameAttribute) attribute:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Models/Book.cs" id="snippet_BookName" highlight="2":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Models/Book.cs" id="snippet_BookName" highlight="2":::
 
    The `[JsonPropertyName]` attribute's value of `Name` represents the property name in the web API's serialized JSON response.
 
 1. Add the following code to the top of `Models/Book.cs` to resolve the `[JsonProperty]` attribute reference:
 
-   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/6.x/BookStoreApi/Models/Book.cs" id="snippet_UsingSystemTextJsonSerialization":::
+   :::code language="csharp" source="~/tutorials/first-mongo-app/samples/8.x/BookStoreApi/Models/Book.cs" id="snippet_UsingSystemTextJsonSerialization":::
 
 1. Repeat the steps defined in the [Test the web API](#test-the-web-api) section. Notice the difference in JSON property names.