Learn ASP. NET Core Razor Programming Series 11--Update the new field to the database

Learn the ASP. NET Core Razor Programming series Catalog

Learn ASP. NET Core Razor programming series One

Learn ASP. NET Core Razor Programming series two--Add an entity

Learn ASP. NET Core Razor Programming series three--Create a data table and create a project basic page

Learn ASP. Razor Programming Series four--asp.net core Razor list template page

Learn ASP. Razor Programming series five--asp.net core Razor new Template page

Learn ASP. NET Core Razor Programming series six--database initialization

Learn ASP. NET Core Razor Programming series seven--Modify List page

Learn ASP. NET Core Razor Programming series eight--concurrent processing

Learn ASP. NET Core Razor programming series nine--Add query function

Learn ASP. NET Core Razor Programming series 10--Add new field

After studying this article, we'll learn how to use the Entity Framework Code first migration feature to add new fields to the model and add new fields to the database at the same time.

When you use EF code first to automatically create a database, Code first adds a table to the database to help track whether the schema of the database is synchronized with the entity class that generated it. If they are not synchronized, EF throws an exception. This makes it easier to find consistent database tables or code problems.

We then use the Code First Migration feature to update the database.

1. Now let's modify the Seeddata class, add a publishing field to the class, and provide the data. Examples of modifications you can refer to each book's information, as shown below.

context.Book.AddRange (
                     new Book
                     {
                         Name = "Python programming from entry to practice",
                         ReleaseDate = DateTime.Parse ("2018-1-12"),
                         Author = "Eric Mathers",
                         Price = 75.99M,
                         Publishing = "Mechanical Publishing"
                     }, 

2. In the visual Studio 2017 menu, choose Build-Build Solution

3. In the visual Studio 2017 menu, choose the Tools menu--NuGet Package Manager > Package Manager Console. Such as.

4. in the PMC, enter the following command,

Add-migration Publishing

The Add-migration directive informs the framework to do the following:

1) Compare the book entity class to the Book table in the database.

2) Create the code to update the table books table structure in the database. Such as.

3) Visual Studio 2017 is named for the migration file with the new field "publishing" as the current date + field name. Such naming helps to manage it. Such as.

5. After executing the instructions above , in the PMC, enter the following command,

Update-database

7. After executing the above instructions, the publishing field is added to the database. Such as.

8. Although we have added a field to the database, there is no data for this field. Such as.

How do you give the field the same value?

1. If you are developing, and have modified the initialization class Seeddata class. Then you can refer to ( Learning ASP. NET Core Razor programming series six-database initialization ) to initialize data to the database.
2. If you delete all the records from the database. You can open the book list page in the browser and then use the delete link to delete the record, or you can use SQL Server Object Explorer (SQL Server Management Studio) to delete the data from the database.

Now that we are running the application in Visual Studio 2017 by pressing F5, the application does not report the same error as in the previous article. After the application is running, open the Create/Edit/list page in the browser to verify that the publishing field's book information is already in the page. Such as.

List page:

To create a page:

Edit page:

Learn ASP. NET Core Razor Programming Series 11--Update the new field to the database