- Entity Framework Auto Generate Key File
- Entity Framework Define Key
- Entity Framework Key Order
- Entity Framework No Primary Key
- Entity Framework Auto Generate Key Download
- In the following example, the AuthorBiographyId property in the AuthorBiography entity does not follow the Entity Framework convention for foreign key names, and it will create an AuthorId field which it will configure as a foreign key.
- Sep 13, 2016 Entity Framework doesn’t support Sequence out of the box. However, there are ways to use it. But the good news is, Entity Framework Core supports Sequence out of the box. I also mentioned in my earlier post Quick summary of what’s new in Entity Framework Core 1.0.So in this post, let’s find out how to use SQL Server Sequence in Entity Framework Core to create primary key.
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Entity Framework 6 EF 6. Home Articles Knowledge Base Online Examples. I am trying to add a record to a table and have the primary key be auto generated. I have the StudentID column as primary key, int. This will automatically generate the student ID for you in the database on row insert and increment the ID by 1 for every new row.
A key serves as a unique identifier for each entity instance. 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). Entities can have additional keys beyond the primary key (see Alternate Keys for more information).
By convention, a property named
Id
or <type name>Id
will be configured as the primary key of an entity.Note
Owned entity types use different rules to define keys.
You can configure a single property to be the primary key of an entity as follows:
Entity Framework Auto Generate Key File
You can also configure multiple properties to be the key of an entity - this is known as a composite 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.
Primary key name
By convention, on relational databases primary keys are created with the name
PK_<type name>
. You can configure the name of the primary key constraint as follows:Key types and values
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. In some cases the key values can be converted to a supported type automatically, otherwise the conversion should be specified manually.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. In that case EF will try to generate a temporary value when the entity is added for tracking purposes. After SaveChanges is called the temporary value will be replaced by the value generated by the database.
Important
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. To avoid this turn off value generation or see how to specify explicit values for generated properties.
Alternate Keys
Entity Framework Define Key
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. 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).
Entity Framework Key Order
Tip
If you just want to enforce uniqueness on a column, define a unique index rather than an alternate key (see Indexes). 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.
Alternate keys are typically introduced for you when needed and you do not need to manually configure them. 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.
Entity Framework No Primary Key
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):
Entity Framework Auto Generate Key Download
Finally, by convention, the index and constraint that are introduced for an alternate key will be named
AK_<type name>_<property name>
(for composite alternate keys <property name>
becomes an underscore separated list of property names). You can configure the name of the alternate key's index and unique constraint: