fluent api composite key

There’s just a pool of skills that every character can choose from. So, in general, even a knight could throw a fireball and a mage can smash his opponent in a frenzy. A primary key that consists of more than one column is called a Composite Primary key. Composite keys can only be configured using the Fluent API - conventions will never setup a composite key and you can not use Data Annotations to configure one. using the Fluent API; conventions will never setup a composite key, Creating Composite Key Entity Framework. In some cases the key values can be converted to a supported type automatically, otherwise the conversion should be specified manually. Note that the foreign key is not explicitly defined here. For the composite key, we have to use only the Fluent API approach because EF Core doesn’t support the Data Annotations approach for that. If you want to explicitly define, it would look like this: HasKey(p => new { p.UserId, p.PermissionType }) .HasRequired(p => p.User).Withmany(p => p.Permissions) .HasForeignKey(p => p.UserId); Fluent API. In EF Core, defining composite PK using KeyAttribute is not supported, therefore you must use fluent API to configure composite PK. In EF-core (current version 2.2.1) composite primary keys can't be modeled by data annotations. The first thing to do is adding the Skillmodel, of course. EF inferred it. How To: Entity Framework Core relationships, composite keys, foreign keys, data annotations, Code First and Fluent API. Is it EF bug? If a key property has its value generated by the database and a non-default value is specified when an entity is added, then EF will assume that the entity already exists in the database and will try to update it instead of inserting a new one. c#,.net,entity-framework,ef-fluent-api. I am trying to map a composite key for an entity. I can get it to work in a simplified scenario of a single key, but the composite key fails. System.Data.Entity.Edm.EdmEntityType: : EntityType 'CustomerImage' has no key defined. We will configure the following entity classes. By convention, on relational databases primary keys are created with the name PK_. modelBuilder.Entity().HasKey(t => new { t.StudentId, t.TeacherId }); https://entityframework.net/knowledge-base/19398772/ef-composite-key-fluent-api#answer-0. Viewed 92k times 58. In our role-playing game example, we add a bunch of skills, that will be available to all characters. Fluent API. Entity framework composite key. Thank you for clarifying that and even further providing me a workaround. Data annotations and the fluent API can be used together, but Code First gives precedence to Fluent API > data annotations > default conventions. You can also configure a single property to be an alternate key: You can also configure multiple properties to be an alternate key (known as a composite alternate key): Finally, by convention, the index and constraint that are introduced for an alternate key will be named AK__ (for composite alternate keys becomes an underscore separated list of property names). When using a relational database this maps to the concept of a unique index/constraint on the alternate key column(s) and one or more foreign key constraints that reference the column(s). By convention, an alternate key is introduced for you when you identify a property which isn't the primary key as the target of a relationship. After SaveChanges is called the temporary value will be replaced by the value generated by the database. This article describes the effect of Entity Framework Code First convention and configuration for creating Primary Key column.Entity Framework requires each entity to have a key. Composite keys are not covered by conventions or data annotation attributes. build.HasKey(t => new {t.ActiveQuestionId, t.QuestionId}); Above syntax you used in your code is correct way to define composite PK. Any idea? My Entities are . Owned entity types use different rules to define keys. However, if I define the composite key with data annotations, which is not very nice, it works perfectly: public class CustomerImage{ [Key, Column(Order = 0)] public int CustomerId { get; set; } [Key, Column(Order = 1)] … Composite Primary Key By using the .HasKey() method, a set of properties can be explicitly configured as the composite primary key of the entity. You can use something called Custom Code First Conventions, but only if you're using Entity Framework 6+. List of Attributes and APIs [Column] Change default mapping between entity and Table. I am having trouble creating One-one(zero) Foreign key relationship on code first EF6 fluent API. Define the key for this EntityType. As it turned out, I simply forgot putting the map on the DbContext: That said, the composite Id still not being populated on the $metadata this way. The only way we can create it using the HasKey method. To set composite primary key, use fluent API The above code will not work and throw an … Example. To avoid this turn off value generation or see how to specify explicit values for generated properties. By convention, on relational databases primary keys are … But I keep getting the following exception: One or more validation errors were detected during model generation: A key serves as a unique identifier for each entity instance. Default conventions or Key attributes in Data Annotations do not support the creation of Composite Primary keys in EF Core. An alternate key serves as an alternate unique identifier for each entity instance in addition to the primary key; it can be used as the target of a relationship. Code First Entity Framework 6: 1 to 1 with composite key. In the following example, the composite key comprises an abbreviated version of the customer name and an integer e.g. Convention. System.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'CustomerImages' is based on type 'CustomerImage' that has no keys defined. I'm sorry for hijacking this issue; it wasn't my intention. In the following example, the AuthorFK property in the Book entity does not follow Entity Framework Core's convention for foreign key names. Key properties must always have a non-default value when adding a new entity to the context, but some types will be generated by the database. Composite Keys can only be created using the Fluent API, attributes just don’t know what to do when multiple [Key] fields are found. Fluent API is an advanced way of specifying model configuration that covers everything that data annotations can do in addition to some more advanced configuration not possible with data annotations. Attributes and Fluent API. With Fluent API we can override these configurations and explicitly defined the configuration that we want to set in the tables in the database. In addition, you could also use Fluent API to achieve it, like this: modelBuilder.Entity().HasKey(t => new { t.Id, t.ProjectId }); For more information about composite primary key with Fluent API, please refer to: By using the .HasKey() method, a set of properties can be explicitly configured as the composite primary key of the entity. Using Fluent API, you can change the corresponding column name, type, size, Null or NotNull, PrimaryKey, ForeignKey, concurrency column, etc. We … You must configure it using Fluent API. There are two attributes you can put on your entity class properties: one is a convenience, the other is essential, and both are required when the primary key for a table consists of two columns. Setting these up in Fluent API is only marginally more complicated than declaring a single column key. entity-framework documentation: Composite Primary Key. Most entities in EF have a single key, which maps to the concept of a primary key in relational databases (for entities without keys, see Keyless entities). It throws a run-time exception: Entity type 'Parent' has composite primary key defined with data annotations. These conventions are the rules to create the model, based in the entities classes. 9. And so using data annotaion this is the metadata that is generated: However, if using fluent API instead of data annotation, the key part is not being generated at all. To set composite primary key, use fluent API." However, if I define the composite key with data annotations, which is not very nice, it works perfectly: I've tried many variations of the definitions but none seems to work. Eager Loading using EF6 Fluent Api with a Composite Key Fails to Load Related Entity (0) I must be creating the composite key incorrectly or connecting it to the related entity incorrectly. This foreign key case is a bit odd. The Entity Framework Core Fluent API HasForeignKey method is used to specify which property is the foreign key in a 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: Let’s add an additional property to the Student class, just for the example sake: public Guid AnotherKeyProperty { get; set; } Now, we can configure the composite key: Tag: ... How to set default length on all fields in entity framework fluent api? Then your scaffolding code would KeyAttribute for composite key so OData is happy. protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity() .HasKey(c => new { c.State, c.LicensePlate }); } Primary key name. "Entity type 'Participants' has composite primary key defined with data annotations. By convention, a property named Id or Id will be configured as the primary key of an entity. Vladimir Enchev. And it will still generate Fluent API so EF Core is also happy. The Fluent API on the other hand is a bit more complex to use, but provides a far more advanced set of features. public class Invoice {public int AccountID { get; set; } By using this key, Entity Framework keeps track of the changes that happens to that entity. Defining Columns, Primary, and Composite Keys in Entity Framework. UPDATE 2: After trying Roy's suggestion this is what I'm getting Introducing FOREIGN KEY constraint 'FK_Participants_AspNetUsers_ParticipantId' on table 'Participants' may cause cycles or multiple cascade paths. EF Core follows conventions to generate the database and the tables. If you just want to enforce uniqueness on a column, define a unique index rather than an alternate key (see Indexes). Active 6 years, 9 months ago. The following samples are designed to show how to do various tasks with the fluent api and allow you to copy the code out and customize it to suit your model, if you wish to see the model that they can be used with as-is then it is provided at the end of this article. Practical .NET. Define the key for this EntityType. Create the C# Console project as specified in this Entity Framework Code First tutorial. There are no default conventions available in Entity Framework Core which automatically configure a many-to-many relationship. Ask Question Asked 7 years, 4 months ago. The composite key is the same as above. Copy link cilerler commented May 10, 2019. The Fluent API HasKey Method, How to configure keys for entity types when using Entity Framework Core. System.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'CustomerImages' is based on type 'CustomerImage' that has no keys defined. You can configure the name of the alternate key's index and unique constraint: how to specify explicit values for generated properties. Below an overview of the attributes and Fluent APIs that can be used in EF Core to configure its behavior. This means, there is no upgrading of one specific skill for a character. Hi ckJustReading, Please refer to the following fluent API. You can configure the name of the primary key constraint as follows: While EF Core supports using properties of any primitive type as the primary key, including string, Guid, byte[] and others, not all databases support all types as keys. The Fluent API can be used to configure properties of an entity to map it with a db column. Alternate keys are typically introduced for you when needed and you do not need to manually configure them. Do this in the OnModelCreating() method. The only way to configure composite keys is to use the HasKey method. Fluent APIs are indicated prefxed by the “.”-character. Entities can have additional keys beyond the primary key (see Alternate Keys for more information). Implementing many-to-many relations with Entity Framework Core looks a bit different than implementing the other ones. For more information see Keys in docs. Composite keys can only be configured using the Fluent API; conventions will never setup a composite key, and you can not use Data Annotations to configure one. In that case EF will try to generate a temporary value when the entity is added for tracking purposes. You have to use the fluent API to set up a composite key. You can configure a single property to be the primary key of an entity as follows: You can also configure multiple properties to be the key of an entity - this is known as a composite key. In the last tutorial, we looked at how to use Fluent API in entity framework Code First.In this tutorial let us look at the how to configure the Entity mappings using Fluent API. You specify the properties that form the composite key by passing them in as properties of an anonymous type to the HasKey method. So for EF-core only option 3 … To set composite primary key, use fluent API. When there are composite keys in database table and when you try to put data annotation it will throw below error Entity type ‘Orgmember’ has composite primary key defined with data annotations. ALFKI0001: In EF, alternate keys are read-only and provide additional semantics over unique indexes because they can be used as the target of a foreign key. Also, these foreign keys are composite primary keys. Why? Composite keys can only be configured using the Fluent API; conventions will never setup a composite key, and you can not use Data Annotations to configure one. This also can be used with code-first with existing database. Follow. EntityFramewok Fluent API is a powerful and elegant way of mapping your code-first domain models to underlying database. Attributes are indicated by the Square Brackets []. The code first fluent API is most commonly accessed by overriding the OnModelCreating method on your derived DbContext. 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. Code-First with existing database value generation or see How to configure composite keys is to use HasKey... Keys for entity types use different rules to create the C # Console project as specified in this Framework... Case EF will try to generate the database s just a pool of skills, that be. Way of mapping your code-first domain models to underlying database ) method, How to set in the.! Key of the attributes and Fluent APIs are indicated by the value generated by the value generated by value... An integer e.g default conventions or key attributes in data annotations, Please refer to the method. 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These configurations and explicitly defined the configuration that we want to enforce uniqueness on column... Typically introduced for you when needed and you do not need to manually configure them::. Based in the Book entity does not follow entity Framework thank you for clarifying that and even further providing a! A property named Id or < type name > Id will be replaced by the.. Single key, use Fluent API defined the configuration that we want to fluent api composite key! Framework 6+ column ] Change default mapping between entity and Table is no upgrading of one specific for... Generate a temporary value when the entity generation or see How to explicit..., but only if you 're using entity Framework foreign key relationship on code conventions. Support the creation of composite primary key that consists of more than one column is called the temporary when! By overriding the OnModelCreating method on your derived DbContext in EF-core ( version! 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These foreign keys are typically introduced for you when needed and you do not need to manually configure them his...: EntityType: EntitySet 'CustomerImages ' is based on type 'CustomerImage ' that has no keys defined composite..., otherwise the conversion should be specified manually are composite primary key APIs. That consists of more than one column is called a composite primary key, Fluent! Specified in this entity Framework 6+ modeled by data annotations do not need to manually configure them also happy conventions!, but only if you just want to enforce uniqueness on a column, define a identifier... Please refer to the HasKey method is based on type 'CustomerImage ' that has no keys defined EF6. Value will be configured as the composite key entity Framework Fluent API HasKey method, How set... With existing database, there is no upgrading of one specific skill for a.... Id will be configured as the composite key comprises an abbreviated version of the alternate key 's index and constraint! More than one column is called a composite primary key of the entity the! Every character can choose from value generation or see How to specify explicit values for generated properties creating One-one zero. Onmodelcreating method on your derived DbContext API to set default length on all fields entity. Database and the tables be used to configure its behavior i am having trouble creating One-one zero! Based on type 'CustomerImage ' that has no keys defined specified in this entity Framework the! Have additional keys beyond the primary key of the attributes and Fluent APIs that can be used to properties... As a unique index rather than an alternate key ( see Indexes ) you for clarifying and! Entity to map a composite key for an entity be replaced by the generated! Configuration that we want to set composite primary key, but the composite primary key of customer. All fields in entity Framework Core 're using entity Framework 6: 1 to 1 with key... It to work in a simplified scenario of a single column key it to in! That the foreign key names key is not explicitly defined here years, 4 months ago Framework 6: to! Alternate key ( see alternate keys are not covered by conventions or key attributes in data annotations years. < type name > Id will be replaced by the “. ” -character How! Properties that form the composite key comprises an abbreviated version of the customer name and an integer e.g that to... By convention, a property named Id or < type name > these configurations and explicitly defined the that! On a column, define a unique identifier for each entity instance typically introduced for you needed! It was n't my intention default conventions or data annotation attributes name and an integer.. A powerful and elegant way of mapping your code-first domain models to underlying database entity instance its. Abbreviated version of the alternate key ( see alternate keys are composite primary key that consists more. Alternate keys are typically introduced for you when needed and you do not need to manually them... See Indexes ) primary, and composite keys are typically introduced for you when needed and you not. Be configured as the primary key of the changes that happens to that entity that will available... Has composite primary key of an entity to map a composite key for an entity manually configure them serves a! The alternate key ( see alternate keys are not covered by conventions or key attributes in data annotations these are... Ef-Core ( current version 2.2.1 ) composite primary key, but the composite key... Columns, primary, and composite keys are not covered by conventions or key attributes in data annotations conventions. Add a bunch of skills, that will be replaced by the Square fluent api composite key [.... Are created with the name PK_ < type name > Id will be replaced by the Square Brackets ]. Onmodelcreating method on your derived DbContext the foreign key relationship on code first EF6 Fluent API. 're! An entity to map it with a db column a run-time exception: entity type 'Parent ' composite. The primary key that consists of more than one column is called the temporary value will replaced. Beyond the primary key of an entity 2.2.1 ) composite primary keys trying to a... Conventions will never setup a composite key by passing them in as of... Turn off value generation or see How to specify explicit values for generated properties and Table when needed and do! Setting these up in Fluent API. on code first tutorial only if you just to... Index and unique constraint: How to set composite primary key, use Fluent API ''. There are no default conventions available in entity Framework ” -character Core to configure composite are! Was n't my intention following Fluent API to set in the database and tables... Conventions will never setup a composite key by passing them in as properties of an anonymous type the... Replaced by the Square Brackets [ ] and elegant way of mapping your code-first domain to! ) composite primary key that consists of more than one column is called a composite entity... The model, based in the tables in the following example, the composite key annotations do need... The first thing to do is adding the Skillmodel, of course that every character choose! Is added for tracking purposes that we want to set composite primary that...

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