60 Modify DBContext for the entity (Publisher). Primary Key and One To Many relations. (Wpf, Xamarin) - chempkovsky/CS2WPF-and-CS2XAMARIN GitHub Wiki
Using “DBContext Wizard” is absolutely necessary
The DBContext Wizard is a tool that creates or modifies an existing DBContext file. There are a lot of such tools. And the question is, "why was it created."
- The answer is as follows:
- Other wizards (ModelViews, WebApiServices) parse the DBContext file and Entities files for their own needs. But the task of creating full-feature parser is a time consuming. On the other hand, only a few fluent api constructs are used by ModelViews, WebApiServices wizards. So, instead of creating a fully functional parser, I created a small code generator for a very short list of constructs. According to (https://www.entityframeworktutorial.net/efcore/configure-one-to-many-relationship-using-fluent-api-in-ef-core.aspx) some fluent api designs can be done in more than one way. To make sure that the ModelViews and WebApiServices wizards parse the fluent api structures correctly, a DBContext Wizard was developed. So, using DBContext Wizard is absolutely necessary. It generates fluent api constructs in a way that ModelViews and WebApiServices wizards parse correctly.
Steps required to accomplish the task
- Step #1:
- Right Click “Literature” of the “Dm02Context”-project and Select “DBContext Wizard” menu item to open the Wizard dialog
- Note:
- On the first page of the dialog the destination folder is shown. The destination folder is the folder in which the generated file will be created.
- Click “Next”-button
- Step #2:
- The developer is on the second page. Now select the "Dm02Context" project and the "LitDbContext" context that has already been created.
- Click “Next”
- Step #3:
- On the third page select “Dm01Entity”-project and “LitPublisher”-entity.
- Click “Add required property to DbContext”
- `DbSet<LitPublisher>`
- property will be added to the context
- Step #4:
- On the same third page, the “Modify”-button became available.
- The developer must explicitly define the primary key.
- Click “Modify”
- Step #5:
- Add ”PublisherId” to the primary key list. The order is important!
- Select “HasKey.Net.cs.t4” template
- Click “Create(Modify)” button. It will add Fluent Api definition of the primary key for “LitPublisher”.
modelBuilder.Entity<LitPublisher>().HasKey(p => p.PublisherId);
Click "Next"-button. You are on the third page again
to define one-to-many (optional-to-many) relation click "Next"-button
- Step #6:
- On the "Foreign Key"-page select "Country" and click "Next"-button
- Step #7:
- On the "Create (Modify) Foreign Key"-page
- select "Iso3CntrRef" and "Iso2CntrRef" fields
- One-to-many
- select "OneToCollection.Net.cs.t4"
- click "Create(Modify)"-button
- On the "Create (Modify) Foreign Key"-page
It will add Fluent Api definition of the foreign key.
modelBuilder.Entity<LitPublisher>().HasRequired(d => d.Country)
.WithMany(m => m.Publishers)
.HasForeignKey(d => new { d.Iso3CntrRef, d.Iso2CntrRef });
- Step #8 (Optional):
- Open “LitDbContext.cs” file
- Find the constructor and change as follows:
public LitDbContext() : base("name=LitConnection") { }