DbExpressionBuilder.RefFromKey Method (EntitySet, DbExpression, EntityType)

.NET Framework (current version)

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

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

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


Type: System.Data.Metadata.Edm.EntitySet

The Entity set in which the referenced element resides.

Type: System.Data.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.

Type: System.Data.Metadata.Edm.EntityType

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

Return Value

Type: System.Data.Common.CommandTrees.DbRefExpression

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

Exception Condition

entitySet, keyRow or entityType is null.


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.

.NET Framework
Available since 4.5
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