EF MVC for 2.0 (#4000)

Author: tdykstra

aspnetcore/data/ef-mvc/advanced.md

@@ -17,9 +17,9 @@ uid: data/ef-mvc/advanced
 
 By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-The Contoso University sample web application demonstrates how to create ASP.NET Core 1.0 MVC web applications using Entity Framework Core 1.0 and Visual Studio 2015. For information about the tutorial series, see [the first tutorial in the series](intro.md).
+The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).
 
-In the previous tutorial you implemented table-per-hierarchy inheritance. This tutorial introduces several topics that are useful to be aware of when you go beyond the basics of developing ASP.NET web applications that use Entity Framework Core.
+In the previous tutorial, you implemented table-per-hierarchy inheritance. This tutorial introduces several topics that are useful to be aware of when you go beyond the basics of developing ASP.NET Core web applications that use Entity Framework Core.
 
 ## Raw SQL Queries
 
@@ -110,20 +110,28 @@ Run the application in debug mode, and go to the Details page for a student.
 Go to the **Output** window showing debug output, and you see the query:
 
 ```
-Microsoft.EntityFrameworkCore.Storage.IRelationalCommandBuilderFactory:Information: Executed DbCommand (225ms) [Parameters=[@__id_0='?'], CommandType='Text', CommandTimeout='30']
-SELECT [e].[EnrollmentID], [e].[CourseID], [e].[Grade], [e].[StudentID], [c].[CourseID], [c].[Credits], [c].[DepartmentID], [c].[Title]
-FROM [Enrollment] AS [e]
+Microsoft.EntityFrameworkCore.Database.Command:Information: Executed DbCommand (56ms) [Parameters=[@__id_0='?'], CommandType='Text', CommandTimeout='30']
+SELECT TOP(2) [s].[ID], [s].[Discriminator], [s].[FirstName], [s].[LastName], [s].[EnrollmentDate]
+FROM [Person] AS [s]
+WHERE ([s].[Discriminator] = N'Student') AND ([s].[ID] = @__id_0)
+ORDER BY [s].[ID]
+Microsoft.EntityFrameworkCore.Database.Command:Information: Executed DbCommand (122ms) [Parameters=[@__id_0='?'], CommandType='Text', CommandTimeout='30']
+SELECT [s.Enrollments].[EnrollmentID], [s.Enrollments].[CourseID], [s.Enrollments].[Grade], [s.Enrollments].[StudentID], [e.Course].[CourseID], [e.Course].[Credits], [e.Course].[DepartmentID], [e.Course].[Title]
+FROM [Enrollment] AS [s.Enrollments]
+INNER JOIN [Course] AS [e.Course] ON [s.Enrollments].[CourseID] = [e.Course].[CourseID]
 INNER JOIN (
-    SELECT DISTINCT TOP(2) [s].[ID]
-    FROM [Person] AS [s]
-    WHERE ([s].[Discriminator] = N'Student') AND ([s].[ID] = @__id_0)
-    ORDER BY [s].[ID]
-) AS [s0] ON [e].[StudentID] = [s0].[ID]
-INNER JOIN [Course] AS [c] ON [e].[CourseID] = [c].[CourseID]
-ORDER BY [s0].[ID]
+    SELECT TOP(1) [s0].[ID]
+    FROM [Person] AS [s0]
+    WHERE ([s0].[Discriminator] = N'Student') AND ([s0].[ID] = @__id_0)
+    ORDER BY [s0].[ID]
+) AS [t] ON [s.Enrollments].[StudentID] = [t].[ID]
+ORDER BY [t].[ID]
 ```
 
-You'll notice something here that might surprise you: the SQL selects up to 2 rows (`TOP(2)`). The `SingleOrDefaultAsync` method doesn't resolve to one row on the server. If the Where clause matches multiple rows, the method must return null, so EF only has to select a maximum of 2 rows, because if 3 or more match the Where clause, the result from the `SingleOrDefault` method is the same as if 2 rows match.
+You'll notice something here that might surprise you: the SQL selects up to 2 rows (`TOP(2)`) from the Person table. The `SingleOrDefaultAsync` method doesn't resolve to 1 row on the server. Here's why:
+
+* If the query would return multiple rows, the method returns null.
+* To determine whether the query would return multiple rows, EF has to check if it returns at least 2.
 
 Note that you don't have to use debug mode and stop at a breakpoint to get logging output in the **Output** window. It's just a convenient way to stop the logging at the point you want to look at the output. If you don't do that, logging continues and you have to scroll back to find the parts you're interested in.
 

aspnetcore/data/ef-mvc/complex-data-model.md

@@ -17,9 +17,9 @@ uid: data/ef-mvc/complex-data-model
 
 By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-The Contoso University sample web application demonstrates how to create ASP.NET Core 1.1 MVC web applications using Entity Framework Core 1.1 and Visual Studio 2017. For information about the tutorial series, see [the first tutorial in the series](intro.md).
+The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).
 
-In the previous tutorials you worked with a simple data model that was composed of three entities. In this tutorial you'll add more entities and relationships and you'll customize the data model by specifying formatting, validation, and database mapping rules.
+In the previous tutorials, you worked with a simple data model that was composed of three entities. In this tutorial, you'll add more entities and relationships and you'll customize the data model by specifying formatting, validation, and database mapping rules.
 
 When you're finished, the entity classes will make up the completed data model that's shown in the following illustration:
 
@@ -83,6 +83,9 @@ Save your changes and build the project. Then open the command window in the pro
 
 ```console
 dotnet ef migrations add MaxLengthOnNames
+```
+
+```console
 dotnet ef database update
 ```
 
@@ -110,6 +113,9 @@ Save your changes and build the project. Then open the command window in the pro
 
 ```console
 dotnet ef migrations add ColumnFirstName
+```
+
+```console
 dotnet ef database update
 ```
 
@@ -420,11 +426,6 @@ dotnet ef migrations add ComplexDataModel
 You get a warning about possible data loss.
 
 ```text
-Build succeeded.
-    0 Warning(s)
-    0 Error(s)
-
-Time Elapsed 00:00:11.58
 An operation was scaffolded that may result in the loss of data. Please review the migration for accuracy.
 Done. To undo this action, use 'ef migrations remove'
 ```

aspnetcore/data/ef-mvc/concurrency.md

@@ -17,9 +17,9 @@ uid: data/ef-mvc/concurrency
 
 By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-The Contoso University sample web application demonstrates how to create ASP.NET Core 1.1 MVC web applications using Entity Framework Core 1.1 and Visual Studio 2017. For information about the tutorial series, see [the first tutorial in the series](intro.md).
+The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).
 
-In earlier tutorials you learned how to update data. This tutorial shows how to handle conflicts when multiple users update the same entity at the same time.
+In earlier tutorials, you learned how to update data. This tutorial shows how to handle conflicts when multiple users update the same entity at the same time.
 
 You'll create web pages that work with the Department entity and handle concurrency errors. The following illustrations show the Edit and Delete pages, including some messages that are displayed if a concurrency conflict occurs.
 
@@ -104,6 +104,9 @@ Save your changes and build the project, and then enter the following commands i
 
 ```console
 dotnet ef migrations add RowVersion
+```
+
+```console
 dotnet ef database update
 ```
 
@@ -175,13 +178,13 @@ In *Views/Departments/Edit.cshtml*, make the following changes:
 
 * Add a "Select Administrator" option to the drop-down list.
 
-[!code-html[Main](intro/samples/cu/Views/Departments/Edit.cshtml?highlight=15,41-43)]
+[!code-html[Main](intro/samples/cu/Views/Departments/Edit.cshtml?highlight=16,34-36)]
 
 ## Test concurrency conflicts in the Edit page
 
 Run the site and click Departments to go to the Departments Index page.
 
-Right click the **Edit** hyperlink for the English department and select **Open in new tab**, then click the **Edit** hyperlink for the English department. The two browser tabs now display the same information.
+Right-click the **Edit** hyperlink for the English department and select **Open in new tab**, then click the **Edit** hyperlink for the English department. The two browser tabs now display the same information.
 
 Change a field in the first browser tab and click **Save**.
 
@@ -238,7 +241,7 @@ If a concurrency error is caught, the code redisplays the Delete confirmation pa
 
 In *Views/Department/Delete.cshtml*, replace the scaffolded code with the following code that adds an error message field and hidden fields for the DepartmentID and RowVersion properties. The changes are highlighted.
 
-[!code-html[Main](intro/samples/cu/Views/Departments/Delete.cshtml?highlight=9,38,43-44)]
+[!code-html[Main](intro/samples/cu/Views/Departments/Delete.cshtml?highlight=9,38,44)]
 
 This makes the following changes:
 
@@ -248,7 +251,7 @@ This makes the following changes:
 
 * Removes the RowVersion field.
 
-* Adds hidden fields for the `DepartmentID` and `RowVersion` properties.
+* Adds a hidden field for the `RowVersion` property.
 
 Run the Departments Index page. Right click the **Delete** hyperlink for the English department and select **Open in new tab**, then in the first tab click the **Edit** hyperlink for the English department.
 
@@ -272,7 +275,7 @@ Replace the code in *Views/Departments/Details.cshtml* to delete the RowVersion
 
 Replace the code in *Views/Departments/Create.cshtml* to add a Select option to the drop-down list.
 
-[!code-html[Main](intro/samples/cu/Views/Departments/Create.cshtml?highlight=38-40)]
+[!code-html[Main](intro/samples/cu/Views/Departments/Create.cshtml?highlight=32-34)]
 
 ## Summary
 

aspnetcore/data/ef-mvc/crud.md

@@ -16,9 +16,9 @@ uid: data/ef-mvc/crud
 
 By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-The Contoso University sample web application demonstrates how to create ASP.NET Core 1.1 MVC web applications using Entity Framework Core 1.1 and Visual Studio 2017. For information about the tutorial series, see [the first tutorial in the series](intro.md).
+The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).
 
-In the previous tutorial you created an MVC application that stores and displays data using the Entity Framework and SQL Server LocalDB. In this tutorial you'll review and customize the CRUD (create, read, update, delete) code that the MVC scaffolding automatically creates for you in controllers and views.
+In the previous tutorial, you created an MVC application that stores and displays data using the Entity Framework and SQL Server LocalDB. In this tutorial, you'll review and customize the CRUD (create, read, update, delete) code that the MVC scaffolding automatically creates for you in controllers and views.
 
 > [!NOTE] 
 > It's a common practice to implement the repository pattern in order to create an abstraction layer between your controller and the data access layer. To keep these tutorials simple and focused on teaching how to use the Entity Framework itself, they don't use repositories. For information about repositories with EF, see [the last tutorial in this series](advanced.md).
@@ -49,7 +49,7 @@ The `AsNoTracking` method improves performance in scenarios where the entities r
 
 The key value that is passed to the `Details` method comes from *route data*. Route data is data that the model binder found in a segment of the URL. For example, the default route specifies controller, action, and id segments:
 
-[!code-csharp[Main](intro/samples/cu/Startup.cs?name=snippet_RouteAndSeed&highlight=5)]
+[!code-csharp[Main](intro/samples/cu/Startup.cs?name=snippet_Route&highlight=5)]
 
 In the following URL, the default route maps Instructor as the controller, Index as the action, and 1 as the id; these are route data values.
 
@@ -153,7 +153,7 @@ The code in *Views/Students/Create.cshtml* uses `label`, `input`, and `span` (fo
 
 Run the page by selecting the **Students** tab and clicking **Create New**.
 
-Enter names and an invalid date and click **Create** to see the error message.
+Enter names and a date. Try entering an invalid date if your browser lets you do that. (Some browsers force you to use a date picker.) Then click **Create** to see the error message.
 
 ![Date validation error](crud/_static/date-error.png)
 

aspnetcore/data/ef-mvc/inheritance.md

@@ -17,9 +17,9 @@ uid: data/ef-mvc/inheritance
 
 By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-The Contoso University sample web application demonstrates how to create ASP.NET Core 1.1 MVC web applications using Entity Framework Core 1.1 and Visual Studio 2017. For information about the tutorial series, see [the first tutorial in the series](intro.md).
+The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).
 
-In the previous tutorial you handled concurrency exceptions. This tutorial will show you how to implement inheritance in the data model.
+In the previous tutorial, you handled concurrency exceptions. This tutorial will show you how to implement inheritance in the data model.
 
 In object-oriented programming, you can use inheritance to facilitate code reuse. In this tutorial, you'll change the `Instructor` and `Student` classes so that they derive from a `Person` base class which contains properties such as `LastName` that are common to both instructors and students. You won't add or change any web pages, but you'll change some of the code and those changes will be automatically reflected in the database.
 
@@ -86,15 +86,7 @@ Save your changes and build the project. Then open the command window in the pro
 dotnet ef migrations add Inheritance
 ```
 
-Run the `database update` command:.
-
-```console
-dotnet ef database update
-```
-
-The command will fail at this point because you have existing data that migrations doesn't know how to handle. You get an error message like the following one:
-
-> The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_CourseAssignment_Person_InstructorID". The conflict occurred in database "ContosoUniversity09133", table "dbo.Person", column 'ID'.
+Don't run the `database update` command yet. That command will result in lost data because it will drop the Instructor table and rename the Student table to Person. You need to provide custom code to preserve existing data.
 
 Open *Migrations\<timestamp>_Inheritance.cs* and replace the `Up` method with the following code:
 
@@ -122,7 +114,7 @@ This code takes care of the following database update tasks:
 
 (If you had used GUID instead of integer as the primary key type, the student primary key values wouldn't have to change, and several of these steps could have been omitted.)
 
-Run the `database update` command again:
+Run the `database update` command:
 
 ```console
 dotnet ef database update