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DbExpressionBuilder.RefFromKey Method (EntitySet, DbExpression)

.NET Framework 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


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.

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).


entitySet or keyRow is null.


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: 4.5.2, 4.5.1, 4.5

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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