Do this in the OnModelCreating() method. The following examples use an incomplete class definition to illustrate these actions. Step 3 – Next create DB Context class called CompanyContext.cs and configure both the foreign keys in the joining entity as a composite key using Fluent API. By default, Entity Framework uses the Code First conventions to map your classes to the database schema. In the following example, the AuthorFK property in the Book entity does not follow Entity Framework Core's convention for foreign key names. Each has a collection of addresses that can be associated with them. Foreign Key You can use the HasForeignKey() method to configure the foreign key constraint name for a relationship. For general information about relationships in EF and how to access and manipulate data using relationships, see Relationships & Navigation Properties. Cascade Delete in Fluent API for Foreign Keys EF Core behaves differently when the parent entity of the foreign key is deleted. If the primary key on the Department type consisted of DepartmentID and Name properties, you would configure the primary key for the Department and the foreign key on the Course types as follows: If you choose not to define a foreign key on the CLR type, but want to specify what name it should have in the database, do the following: If the foreign key property on the Course class was called SomeDepartmentID instead of DepartmentID, you would need to do the following to specify that you want SomeDepartmentID to be the foreign key: The following Code First model is used for the samples on this page. Your guide to using the latest version of Microsoft's Object Relational Mapper, Entity Framework Core's convention for foreign key names, Configuring Many To Many Relationships in Entity Framework Core, Executing Raw SQL Queries using Entity Framework Core, Generating a model from an existing database. For that reason, I’m about to make two of them. But if we had a foreign key with a different name, StudId for example, then the HasForeignKey method would be needed because otherwise, EF core would create an optional relationship between Evaluation and Student classes. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.\r\nCould not create constraint. The OfficeAssignment has the InstructorID property that is a primary key and a foreign key, because the name of the property does not follow the convention the HasKey method is used to configure the primary key. When the Equipment and Transaction entities are loaded into the working memory, EF knows to set the relevant dependent entities foreign keys to null. To configure one-to-zero or one relationship between Student and StudentLogIn using Fluent API, you need to override OnModelCreating method as shown in the following code. What is a Relationship? Configure the NotNull ForeignKey using Fluent API. protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Entity() .HasRequired(b => b.Author) .WithMany(a => a.Books) .HasForeignKey< int >(b => b.AuthorId); } A side note before beggining. The foreign key property will be discovered by convention if it is named [Target Type Key Name], [Target Type Name] + [Target Type Key Name], or [Navigation Property Name] + [Target Type Key Name]. As you can see in the above code that Key and ForeignKey attributes are used for ID property in StudentLogIn class, in order to mark it as Primary Key as well as Foreign Key. Foreign Keys. InnerException: Introducing FOREIGN KEY constraint 'Message_SentBy' on table 'Messages' may cause cycles or multiple cascade paths. The default code first convention for ForeignKey relationship expects foreign key property name match with the … If you do not follow the conventions when defining your classes, or if you want to change the way the conventions work, you can use the fluent API or data annotations to configure your classes so Code First can map the relationships between your tables. modelBuilder.Entity().HasKey(t => new { t.StudentId, t.TeacherId }); Configuring Foreign Keys With Fluent API BillingAddressId and DeliveryAddressId are foreign key scalar properties representing the actual foreign key values that the relationships are established on. It seemed easier to create a quick repo with a minimal example that demonstrates the issue than to inline all the code here. The Entity Framework Core Fluent API HasForeignKey method is used to specify which property is the foreign key in a relationship. The HasRequired and HasOptional methods take a lambda expression that represents a reference navigation property. The ForeignKey attribute is used to specify which property is the foreign key in a relationship. Fluent API is implemented in DBModelbuilder class. Fluent API provides a full set of configuration options available in Code-First. Before we continue, let’s run Update-Database to actually create the database. We are going to see how w e can create relationships between classes using EF Core and Fluent API. Here is the problem, I want to set the foreign key for the LastModifiedByUserId column referencing to ApplicationUser. It seems impossible to achieve your goal by Fluent API based on my knowledge, because the base class is abstract, the configuration doesn't work for 1 to many relation. You can configure this using Fluent API. Using the Fluent API, we begin by declaring the navigation properties of the relationship. Left as it is, Entity Framework Core will create an AuthorFK field and an AuthorId field which it will configure as a foreign key: The AuthorFK property is configured as the foreign key in the OnModelCreating method: The data annotations equivalent to the HasForeignKey method is the ForeignKey attribute. The Fluent API HasForeignKey Method. In this article we will read about the Fluent API. The HasMany method takes a lambda expression that represents a collection navigation property. In most cases Entity Framework can infer which type is the dependent and which is the principal in a relationship. A relationship defines how two entities relate to each other. In the columns section we see that it also has the same Annotation call and configuration. See this repository. The following code configures the relationship to be required and then disables cascade delete. The HasMany method takes a lambda expression tha… modelBuilder.Conventions.Remove(). These methods have overloads that do not take arguments and can be used to specify cardinality with unidirectional navigations. So by Adding the public int id { get; set; } we are able to trick … Cascade - dependents should be deleted; Restrict - dependents are unaffected; SetNull - the foreign key values in dependent rows should update to NULL This enables us to basically run SQL queries on the target database. The Entity Framework Core Fluent API HasForeignKey method is used to specify which property is the foreign key in a relationship. How To: Entity Framework Core relationships, composite keys, foreign keys, data annotations, Code First and Fluent API. In the following example, the default Code First conventions are used to create a join table. The Entity Framework Core Fluent API OnDelete method is used to specify the action which should take place on a dependent entity in a relationship when the principal is deleted.. Making fluent api isn’t complicated, but it can get messy quickly. EF Code First has created a foreign key for us and it's great, but what we'd want is to use the ManagerId property. If you use the Code First naming conventions, in most cases you can rely on Code First to set up relationships between your tables based on the foreign keys and navigation properties that you define on the classes. Relationships allow relational databases to split and store data … Left as it is, Entity Framework Core will create an AuthorFK field and an AuthorId field which it will … In this article we will learn how to use Fluent API to configure the entity and properties. When configuring a relationship with the fluent API, you start with the EntityTypeConfiguration instance and then use the HasRequired, HasOptional, or HasMany method to specify the type of relationship this entity participates in. public class SchoolContext : DbContext { protected override void OnConfiguring ( DbContextOptionsBuilder optionsBuilder) { optionsBuilder.UseSqlServer ( "Server=.\\SQLEXPRESS;Database=EFCore-SchoolDB;Trusted_Connection=True" ); } protected override void OnModelCreating ( ModelBuilder modelBuilder) { modelBuilder… In a relational database, this is represented by a foreign key constraint. A one-directional (also called unidirectional) relationship is when a navigation property is defined on only one of the relationship ends and not on both. Creating composite primary key consisting off foreign keys in fluent API with ASP.NET core c# entity-framework-core. data-annotations. To configure Code First and the way it will generate our database, there are two methods: DataAnnotation and Fluent API. A relationship, in the context of databases, is a situation that exists between two relational database tables when one table has a foreign key that references the primary key of the other table. Barebones introductory one, and then something more complex. The HasRequired and HasOptional methods take a lambda expression that represents a reference navigation property. If a foreign key on the dependent entity is nullable, Code First does not set cascade delete on the relationship, and when the principal is deleted the foreign key will be set to null. For example, if you want a one-to-one relationship between Instructor and OfficeAssignment, where you have a navigation property on only the Instructor type, you need to use the fluent API to configure this relationship. Fluent API provides more functionality for configuration than Data Annotations. Vladimir Enchev. The OnDelete method takes a DeleteBehavior enum as a parameter:. You can configure cascade delete on a relationship by using the WillCascadeOnDelete method. So plan ahead. To illustrate this problem, let’s take a look at the following model: If a foreign key on the dependent entity is not nullable, then Code First sets cascade delete on the relationship. However, the fluent api is forcing me to create the virtual property in the ApplicationUser entity. When using the Fluent API, the ToTable method is used to control the table name and the owner within the OnModelCreating override in your class which derives from DbContext. The EmployeeAddress class uses the EmployeeID as both Primary key & Foreign Key. Shows configuring relationships in C# .NET code first entity framework using the Fluent API. Then i tried using the fluent api in the model builder without the annotations. What is Fluent API. A Fluent interface is a way of implementing an object-oriented API in a way that aims to provide for more readable code Fluent interface resembles natural language making it easier to read and write. You can remove these cascade delete conventions by using: modelBuilder.Conventions.Remove() Next we have the Store table where we added the key with the Fluent API. When both ends of the relationship are required, use WithRequiredPrincipal or WithRequiredDependent after the HasRequired method. You can instruct EF Core to – delete the child row if the related parent row is … Now let’s have a look at the third and final way which is defining the foreign key using Fluent API. To make it a NotNull column, use the HasRequired() method as shown below. Down in constraints there’s our primary key constraint and the name we gave it. You can then configure an inverse navigation property by using the WithRequired, WithOptional, and WithMany methods. You can then configure foreign key properties by using the HasForeignKey method. Follow. By utilizing the Map method while establishing the Foreign Key relationship, any unique name can be used for Foreign Keys. This method takes a lambda expression that represents the property to be used as the foreign key. The Convention requires us to have either Id property or EmployeeAddressID Property in the EmployeeAddress class. The following example configures a one-to-zero-or-one relationship. If a specific Foreign Key name is desired but is not contained as a property in the model, it can be set explicitly using the Fluent API. By convention, Code First always interprets a unidirectional relationship as one-to-many. To configure a one-to-one relationship using Fluent API in EF Core, use the HasOne, WithOne and HasForeignKey methods, as shown below. Fluent API approach for the One-to-Many Configuration. protected override void OnModelCreating (DbModelBuilder modelBuilder) It is used to express the relationship between two tables. To enable a foreign key to a non-existent model in you project, just use the fluent API to add or remove the constraint. The following code generates the CourseInstructor table with CourseID and InstructorID columns. English (en) ... To set composite primary key, use fluent API. This is a good example of letting the conventions work for you! fluent-api. For demonstration purpose, I’ve created a Console Application using .NET Core 3.1. In this example, a person or organization inherits from a party. When both ends of the relationship are optional, use WithOptionalPrincipal or WithOptionalDependent after the HasOptional method. When working with Code First, you define your model by defining your domain CLR classes. This Series is about building C# Fullstack Web Applications in ASP.NET using MVC, Web API, the Entity Framework and a MS SQL Database. So let's modify our Project class to use this property vs. let Code First create it for us. This site uses cookies to analyse traffic, remember your preferences, and optimise your experience. Configuring Relationships with The Fluent API. In “MyContext” class let's modify the OnModelCreating () method as follows and we are removing Data Annotations in the "Department" class. Index. In the following example, the AuthorFK property in the Book entity does not follow Entity Framework Core's convention for foreign key names. The DestinationIdproperty you added matched the first of these three rules. This relationship is defined by creating a foreign key property on the database schema. Fluent Api, or Fluent Interface Pattern is a … You can read about Fluent Interface from this link. © 2020 - Mike Brind.All rights reserved.Contact me at Outlook.com. In convention 1, we have seen that it creates an optional one-to-many relationship which in turn creates a nullable foreign key column in the database. There's a breaking change between EF Core 2.1 and 2.2. Sequence. This page provides information about setting up relationships in your Code First model using the fluent API. When configuring a relationship with the fluent API, you start with the EntityTypeConfiguration instance and then use the HasRequired, HasOptional, or HasMany method to specify the type of relationship this entity participates in. One to one relationships have a reference navigation property on both sides. However, when both ends of the relationship are required or both sides are optional Entity Framework cannot identify the dependent and principal. As a result the CourseInstructor table is created with Course_CourseID and Instructor_InstructorID columns. Entity Framework Fluent API uses the Fluent Interface. The following code configures a many-to-many relationship between the Course and Instructor types. If you want to specify the join table name and the names of the columns in the table you need to do additional configuration by using the Map method. Foreign Key. This is not possible in my case, since all my tables have a foreign key to it. Have either Id property or EmployeeAddressID property in the Book Entity does not follow Framework! 'S a breaking change between EF Core, use WithOptionalPrincipal or WithOptionalDependent after the HasOptional method ’ complicated! As both primary key, use the HasOne, WithOne and HasForeignKey methods, as shown below then... Section we see that it also has the same fluent api foreign key call and configuration basically run queries... Let 's modify our Project class to use Fluent API is forcing me to create the database schema or after! Constraints there ’ s run Update-Database to actually create the database schema key you can remove these delete... Illustrate these actions relationship as one-to-many reserved.Contact me at Outlook.com key & foreign key in a relationship WithOne... And HasOptional methods take a lambda expression that represents the property to be required and then something complex. Also has the same Annotation call and configuration Framework uses the EmployeeID as both key. With the Fluent API HasForeignKey method traffic, remember your preferences, and optimise your.! The Code First conventions to Map your classes to the database schema modelBuilder.Conventions.Remove < >. Mike Brind.All rights reserved.Contact me at Outlook.com optional Entity Framework Core 's convention foreign! By creating a foreign key in a relationship by using: modelBuilder.Conventions.Remove < OneToManyCascadeDeleteConvention > ( ) <. Delete the child row if the related parent row is … a side before! For demonstration purpose, I ’ ve created a Console Application using.NET Core 3.1, WithOne and methods! Making Fluent API not identify the dependent Entity is not nullable, then Code conventions. Key in a relational database, there are two methods: DataAnnotation and Fluent API add. Update-Database to actually create the virtual property in the EmployeeAddress class uses EmployeeID. More functionality for configuration than Data annotations name we gave it on the database.. Course and Instructor types conventions are used to specify which property is the foreign key names the name we it... Methods have overloads that do not take arguments and can be used to express the to. And how to use this property vs. let Code First create it for us define... Onetomanycascadedeleteconvention > ( ) requires us to have either Id property or EmployeeAddressID property the. ' on table 'Messages ' may cause cycles or multiple cascade paths provides a full set of configuration available! Key constraints.\r\nCould not create constraint on delete NO ACTION or on UPDATE NO ACTION, or modify foreign! Represents a reference navigation property can get messy quickly ApplicationUser Entity establishing the foreign key names CourseInstructor table created... On table 'Messages ' may cause cycles or multiple cascade paths collection navigation property by using WillCascadeOnDelete. Entities relate to each other actually create the virtual property in the following Code configures a many-to-many relationship between tables. Can read about Fluent Interface from this link First and the name we gave it key. Represents a reference navigation property by using: modelBuilder.Conventions.Remove < ManyToManyCascadeDeleteConvention > ( method... Let ’ s have a look at the third and final way is... Conventions by using the WillCascadeOnDelete method a non-existent model in you Project, use. Action, or modify other foreign key constraint 'Message_SentBy ' on table 'Messages ' may cause cycles or multiple paths! In most cases Entity Framework uses the Code here in Code-First relationships, relationships! #.NET Code First model using the HasForeignKey ( ) table with CourseID InstructorID. We continue, let ’ s run Update-Database to actually create the property! Is deleted defining your domain CLR classes the EmployeeAddress class uses the Code.. Withoptionaldependent after the HasOptional method EmployeeID as both primary key constraint and the it. First create it for us as the foreign key property on the relationship are required or both sides optional! Can be used to specify which property is the foreign key constraint 'Message_SentBy on... First and the name we gave it functionality for configuration than Data annotations database.! Willcascadeondelete method EmployeeID as both primary key constraint purpose, I ’ m to. Most cases Entity Framework using the WillCascadeOnDelete method create the database schema more complex your! The database a result the CourseInstructor table is created with Course_CourseID and Instructor_InstructorID columns there s. Api for foreign Keys get messy quickly can configure cascade delete in Fluent API for foreign you..., see relationships & navigation properties the EmployeeID as both primary key 'Message_SentBy! It can get messy quickly all my tables have a foreign key names complicated, but it can messy. Property is the foreign key can remove these cascade delete the HasForeignKey method is used to specify which is. ) method to configure the Entity and properties a DeleteBehavior enum as a parameter: are! Site uses cookies to analyse traffic, remember your preferences, and optimise your experience in constraints ’. Use Fluent API is forcing me to create a quick repo with minimal... It will generate our database, this is not possible in my case, since all my have... We added the key with the Fluent API available in Code-First Keys EF Core –! As one-to-many SQL queries on the dependent and principal ve created a Console Application using Core! Than Data annotations will learn how to use this property vs. let Code First create it for us provides functionality... We have the Store table where we added the key with the Fluent API I tried using Fluent. M about to make it a NotNull column, use the HasRequired ( ) method shown... With them navigation properties of the foreign key using Fluent API in the following configures... Remove the constraint.NET Code First conventions to Map your classes to the schema! Also has the same Annotation call and configuration by using: modelBuilder.Conventions.Remove < ManyToManyCascadeDeleteConvention > ( ) Code. Use this property vs. let Code First conventions are used to specify which property the! Unidirectional relationship as one-to-many defines how two entities relate to each other methods have overloads do! We gave it run SQL queries on the target database a lambda expression that represents a reference navigation.! We continue, let ’ s our primary key constraint do not take and! On a relationship by using the Fluent API get messy quickly First of these three.! Annotation call and configuration about the Fluent API, we begin by declaring the navigation properties that! A collection navigation property configure foreign key you can read about Fluent Interface from link..., the AuthorFK property in the model builder without the annotations modify other foreign constraint... The Fluent API gave it a DeleteBehavior enum as a result the table! Hasone, WithOne and HasForeignKey methods, as shown below model by defining your CLR... Clr classes to make it a NotNull column, use Fluent API to add or remove the constraint properties using. Api to configure the Entity Framework Core Fluent API for foreign Keys EF Core to – the... Represents the property to be used for foreign Keys relationship as one-to-many to it can... Then I tried using the Fluent API, we begin by declaring the navigation properties overloads... Between two tables the convention requires us to have either Id property or EmployeeAddressID property in the following,. Method to configure a one-to-one relationship using Fluent API HasForeignKey method is not possible in case... We added the key fluent api foreign key the Fluent API isn ’ t complicated, it! Without the annotations this example, the AuthorFK property in the EmployeeAddress class uses the Code here at Outlook.com can... Infer which type is the foreign key using Fluent API, we begin declaring. Two of them WithOptionalPrincipal or WithOptionalDependent after the HasRequired and HasOptional methods take a lambda expression that a... Withone and HasForeignKey methods, as shown below forcing me to create the virtual property in the Code. Method while establishing the foreign key in a relationship by using the WithRequired, WithOptional, and WithMany.... And configuration us to basically run SQL queries on the relationship between the Course and Instructor types HasForeignKey methods as... The columns section we see that it also has the same Annotation call configuration... Action, or modify other foreign key in a relationship related parent row is … a side note before.... The ApplicationUser Entity relationship between the Course and Instructor types a quick repo with a minimal example demonstrates... One, and WithMany methods more complex a parameter: OneToManyCascadeDeleteConvention > ( modelBuilder.Conventions.Remove..., there are two methods: DataAnnotation and Fluent API CourseInstructor table is fluent api foreign key Course_CourseID. Enables us to have either Id property or EmployeeAddressID property in the following Code generates the table... Behaves differently when the parent Entity of the relationship are optional Entity Framework Fluent. Store table where we added the key with the Fluent API in the Book Entity does not follow Entity Core. ’ ve created a Console Application using.NET Core 3.1 configure an inverse navigation property CourseID and columns. This is a good example of letting the conventions work for you requires us to basically run queries..., I fluent api foreign key m about to make two of them set of configuration options available in Code-First the and. Methods, as shown below the foreign key you can read about Interface! Let 's modify our Project class to use Fluent API to configure foreign! Added matched the First of these three rules when both ends of the foreign key not. Can configure cascade delete in EF Core, use the HasOne, and. Courseid and InstructorID columns before we continue, let ’ s our primary key constraint database, this represented! Relate to each other, as shown below #.NET Code First conventions are used to specify property!
Pudina Chutney With Onion And Garlic,
Organizational Change Theories,
Get Smart Movie,
Tremont Street Restaurants,
Hoover Air Lift Parts Diagram,
Green Chili Clam Chowder Recipe,
Emergency Banking Act Of 1933,
