Configure One-to-Many Relationship in Entity Framework 6
Configure One-to-Many Relationships in EF 6. Here (domain classes) in Entity Framework 6.x using the code-first approach. the one-to-many relationship in the above entities, the database tables for one-to-one relationship in code first. Creating a relationship is not that tricky and certainly not impossible, although it is not a particularly common requirement and in this case I can't see why you. The Entity Framework Code First approach allows us to create a model as a plain class and then the database gets created from the domain.
Updating many to many relationships in Entity Framework Core – The Reformed Programmer
Oh, and it's now fully open-sourcedwith the most recent version V7 in beta and located here. For this post, we'll be using EF6. Why should I use it? Because SqlConnection and SqlCommand are old, creaky classes that can be replaced by new, shinier classes? Actually, primary reason you'd want to use EF is because Visual Studio makes it really easy to design a model or use an already-existing database to make a model in EF.
The barriers to entry are really low. How do I get started? This demo assumes that you already have a database that exists that you would like to use. Create a project in Visual Studio it could be any kind of project, but for this demo we will be using a command line application. Once you've got the project created, right-click on the folder where you want your model to exist and select Add a New Item. On this dialog, select ADO. This will bring up the Choose Model Contents dialog unless your project doesn't have Entity Framework installed, in which case you'll be prompted to select what version of EF you want.
Get Version 6 if it is an option. We're going to build an EF Designer model from a database. In a later installment of this series we'll also build a CodeFirst model from the same database so we can show the differences between the two. For right now click Next, which will open the Data Connection dialog.
Rename your connection string to whatever you like I'm calling mine "Northwind Entities" and hit Next, which opens the Database Objects and Settings dialog. On this dialog you can select all items from the database that you want to be modeled.
For this demo, we'll be using all Tables and Stored Procedures in the Northwind database. That's a lot of dialogs, but hey, this is the last step.
Click Finish to generate your model. Once the code generation is complete, you'll see a new EDMX file in your project: Open that file to see a database diagram. Mine looks like this: Well now, that looks like a well-formed database.Lab 23 OneToOne And OneToMany Relationship in MVC and entity framework
But, what are those other files besides the EDMX? Let's break them down.
This example produces the same result in the database as convention 1. Convention 3 Including navigation properties at both ends will also result in a one-to-many relationship, as shown below. Convention 4 A fully defined relationship at both ends will create a one-to-many relationship, as shown below.
This will create a one-to-many relationship with the NotNull foreign key column in the Students table, as shown below. If the data type of GradeId is nullable integer, then it will create a null foreign key.
Exception Not Found
However, you may configure relationships using Fluent API at one place to make it more maintainable. Consider the following Student and Grade entity classes. First, we need to start configuring with any one entity class. CurrentGrade specifies that the Student entity has required the CurrentGrade property.
This will create a NotNull foreign key column in the DB. Now, it's time to configure the other end of the relationship - the Grade entity. Students specifies that the Grade entity class includes many Student entities.
Here, many infers the ICollection type property. Now, if the Student entity does not follow the Id property convention for foreign key, then we can specify the name of the foreign key using the HasForeignKey method. CurrentGradeId ; specifies the foreign key property in the Student entity. Alternatively, you can start configuring the relationship with the Grade entity instead of the Student entity.