ReferenceCollectionBuilder<TPrincipalEntity,TDependentEntity>.HasForeignKey Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Overloads
| HasForeignKey(Expression<Func<TDependentEntity,Object>>) |
Configures the property(s) to use as the foreign key for this relationship. |
| HasForeignKey(String[]) |
Configures the property(s) to use as the foreign key for this relationship. |
HasForeignKey(Expression<Func<TDependentEntity,Object>>)
Configures the property(s) to use as the foreign key for this relationship.
public virtual Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceCollectionBuilder<TPrincipalEntity,TDependentEntity> HasForeignKey (System.Linq.Expressions.Expression<Func<TDependentEntity,object>> foreignKeyExpression);public virtual Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceCollectionBuilder<TPrincipalEntity,TDependentEntity> HasForeignKey (System.Linq.Expressions.Expression<Func<TDependentEntity,object?>> foreignKeyExpression);override this.HasForeignKey : System.Linq.Expressions.Expression<Func<'DependentEntity, obj>> -> Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceCollectionBuilder<'PrincipalEntity, 'DependentEntity (requires 'PrincipalEntity : null and 'DependentEntity : null)>Public Overridable Function HasForeignKey (foreignKeyExpression As Expression(Of Func(Of TDependentEntity, Object))) As ReferenceCollectionBuilder(Of TPrincipalEntity, TDependentEntity)Parameters
- foreignKeyExpression
- Expression<Func<TDependentEntity,Object>>
A lambda expression representing the foreign key property(s) (post => post.BlogId).
If the foreign key is made up of multiple properties then specify an anonymous type including the
properties (comment => new { comment.BlogId, comment.PostTitle }). The order specified should match the order of
corresponding properties in HasPrincipalKey(Expression<Func<TPrincipalEntity,Object>>).
Returns
The same builder instance so that multiple configuration calls can be chained.
Remarks
If HasPrincipalKey(Expression<Func<TPrincipalEntity,Object>>) is not specified, then an attempt will be made to match the data type and order of foreign key properties against the primary key of the principal entity type. If they do not match, new shadow state properties that form a unique index will be added to the principal entity type to serve as the reference key. A shadow state property is one that does not have a corresponding property in the entity class. The current value for the property is stored in the ChangeTracker rather than being stored in instances of the entity class.
Applies to
HasForeignKey(String[])
Configures the property(s) to use as the foreign key for this relationship.
public virtual Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceCollectionBuilder<TPrincipalEntity,TDependentEntity> HasForeignKey (params string[] foreignKeyPropertyNames);override this.HasForeignKey : string[] -> Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceCollectionBuilder<'PrincipalEntity, 'DependentEntity (requires 'PrincipalEntity : null and 'DependentEntity : null)>Public Overridable Function HasForeignKey (ParamArray foreignKeyPropertyNames As String()) As ReferenceCollectionBuilder(Of TPrincipalEntity, TDependentEntity)Parameters
- foreignKeyPropertyNames
- String[]
The name(s) of the foreign key property(s).
Returns
The same builder instance so that multiple configuration calls can be chained.
Remarks
If the specified property name(s) do not exist on the entity type then a new shadow state property(s) will be added to serve as the foreign key. A shadow state property is one that does not have a corresponding property in the entity class. The current value for the property is stored in the ChangeTracker rather than being stored in instances of the entity class.
If HasPrincipalKey(Expression<Func<TPrincipalEntity,Object>>) is not specified, then an attempt will be made to match the data type and order of foreign key properties against the primary key of the principal entity type. If they do not match, new shadow state properties that form a unique index will be added to the principal entity type to serve as the reference key.
Applies to
Entity Framework