DbExpressionBuilder.RefFromKey Method

 

Creates a new DbRefExpression that encodes a reference to a specific Entity based on key values.

Namespace:   System.Data.Entity.Core.Common.CommandTrees.ExpressionBuilder
Assembly:  EntityFramework (in EntityFramework.dll)

NameDescription
System_CAPS_pubmethodSystem_CAPS_staticRefFromKey(EntitySet, DbExpression)

Creates a new DbRefExpression that encodes a reference to a specific Entity based on key values.

System_CAPS_pubmethodSystem_CAPS_staticRefFromKey(EntitySet, DbExpression, EntityType)

Creates a new DbRefExpression that encodes a reference to a specific Entity based on key values.


DbExpressionBuilder.RefFromKey Method (EntitySet, DbExpression)

Creates a new DbRefExpression that encodes a reference to a specific Entity based on key values.

public static DbRefExpression RefFromKey(
	this EntitySet entitySet,
	DbExpression keyRow
)

Parameters

entitySet
Type: System.Data.Entity.Core.Metadata.Edm.EntitySet

The Entity set in which the referenced element resides.

keyRow
Type: System.Data.Entity.Core.Common.CommandTrees.DbExpression

A DbExpression that constructs a record with columns that match (in number, type, and order) the Key properties of the referenced Entity type.

Return Value

Type: System.Data.Entity.Core.Common.CommandTrees.DbRefExpression

A new DbRefExpression that references the element with the specified key values in the given Entity set.

Exception Condition
ArgumentNullException

entitySet or keyRow is null.

ArgumentException

keyRow

keyRow should be an expression that specifies the key values that identify the referenced entity within the given entity set.The result type of keyRow should contain a corresponding column for each key property defined byentitySet's entity type.


DbExpressionBuilder.RefFromKey Method (EntitySet, DbExpression, EntityType)

Creates a new DbRefExpression that encodes a reference to a specific Entity based on key values.

public static DbRefExpression RefFromKey(
	this EntitySet entitySet,
	DbExpression keyRow,
	EntityType entityType
)

Parameters

entitySet
Type: System.Data.Entity.Core.Metadata.Edm.EntitySet

The Entity set in which the referenced element resides.

keyRow
Type: System.Data.Entity.Core.Common.CommandTrees.DbExpression

A DbExpression that constructs a record with columns that match (in number, type, and order) the Key properties of the referenced Entity type.

entityType
Type: System.Data.Entity.Core.Metadata.Edm.EntityType

The type of the Entity that the reference should refer to.

Return Value

Type: System.Data.Entity.Core.Common.CommandTrees.DbRefExpression

A new DbRefExpression that references the element with the specified key values in the given Entity set.

Exception Condition
ArgumentNullException

entitySet, keyRow or entityType is null.

ArgumentException

entityType is not in the same type hierarchy as the entity set's entity type, or keyRow does not have a record result type that matches the key properties of the referenced entity set's entity type.

keyRow should be an expression that specifies the key values that identify the referenced entity within the given entity set. The result type of keyRow should contain a corresponding column for each key property defined by entitySet's entity type.