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DbExpressionBuilder.RefFromKey Method (EntitySet, DbExpression, EntityType)

.NET Framework 4.6 and 4.5

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
)

Parameters

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

The Entity set in which the referenced element resides.

keyRow
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.

entityType
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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type EntitySet. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
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.

.NET Framework

Supported in: 4.6, 4.5
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