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Expression.PropertyOrField Method

Creates a MemberExpression that represents accessing a property or field.

Namespace:  System.Linq.Expressions
Assembly:  System.Core (in System.Core.dll)

'Declaration
Public Shared Function PropertyOrField ( _
	expression As Expression, _
	propertyOrFieldName As String _
) As MemberExpression

Parameters

expression
Type: System.Linq.Expressions.Expression

An Expression whose Type contains a property or field named propertyOrFieldName. This can be null for static members.

propertyOrFieldName
Type: System.String

The name of a property or field to be accessed.

Return Value

Type: System.Linq.Expressions.MemberExpression
A MemberExpression that has the NodeType property equal to MemberAccess, the Expression property set to expression, and the Member property set to the PropertyInfo or FieldInfo that represents the property or field denoted by propertyOrFieldName.

ExceptionCondition
ArgumentNullException

expression or propertyOrFieldName is Nothing.

ArgumentException

No property or field named propertyOrFieldName is defined in expression.Type or its base types.

The Type property of the resulting MemberExpression is equal to the PropertyType or FieldType properties of the PropertyInfo or FieldInfo, respectively, that represents the property or field denoted by propertyOrFieldName.

This method searches expression.Type and its base types for a property or field that has the name propertyOrFieldName. Public properties and fields are given preference over non-public properties and fields. Also, properties are given preference over fields. If a matching property or field is found, this method passes expression and the PropertyInfo or FieldInfo that represents that property or field to Property or Field, respectively.

The following example shows how to create an expression that represents accessing a property or field.

' Add the following directive to your file: 
' Imports System.Linq.Expressions   

Class TestClass
    Public Property Sample As Integer 
End Class 

Sub TestPropertyOrField()

    Dim obj As New TestClass()
    obj.Sample = 40

    ' This expression represents accessing a property or field. 
    ' For static properties or fields, the first parameter must be Nothing. 
    Dim memberExpr As Expression = Expression.PropertyOrField(
          Expression.Constant(obj),
          "Sample"
      )

    ' The following statement first creates an expression tree, 
    ' then compiles it, and then runs it.
    Console.WriteLine(Expression.Lambda(Of Func(Of Integer))(memberExpr).Compile()())
End Sub 

' This code example produces the following output: 

' 40

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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