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Expression.ArrayAccess Method (Expression, Expression())

Creates an IndexExpression to access an array.

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

'Declaration
Public Shared Function ArrayAccess ( _
	array As Expression, _
	ParamArray indexes As Expression() _
) As IndexExpression

Parameters

array
Type: System.Linq.Expressions.Expression

An expression representing the array to index.

indexes
Type: System.Linq.Expressions.Expression()

An array that contains expressions used to index the array.

The expression that represents the array can be obtained by using the MakeMemberAccess method, or through NewArrayBounds or NewArrayInit.

For multidimensional arrays, use the ArrayAccess method.

The following code example shows how to change a value of an array element by using the ArrayAccess method.

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

' This parameter expression represents a variable that will hold the array. 
Dim arrayExpr As ParameterExpression = Expression.Parameter(GetType(Integer()), "Array")

' This parameter expression represents an array index. 
' For multidimensional arrays, you can define several indexes.  
Dim indexExpr As ParameterExpression = Expression.Parameter(GetType(Integer), "Index")

' This parameter represents the value that will be added to a corresponding array element. 
Dim valueExpr As ParameterExpression = Expression.Parameter(GetType(Integer), "Value")

' This expression represents an array access operation. 
' It can be used for assigning to, or reading from, an array element. 
Dim arrayAccessExpr As Expression = Expression.ArrayAccess(
    arrayExpr,
    indexExpr
)

' This lambda expression assigns a value provided to it to a specified array element. 
' The array, the index of the array element, and the value to be added to the element 
' are parameters of the lambda expression. 
Dim lambdaExpr As Expression(Of Func(Of Integer(), Integer, Integer, Integer)) =
    Expression.Lambda(Of Func(Of Integer(), Integer, Integer, Integer))(
        Expression.Assign(arrayAccessExpr, Expression.Add(arrayAccessExpr, valueExpr)),
    arrayExpr,
    indexExpr,
    valueExpr
  )

' Print expressions.
Console.WriteLine("Array Access Expression:")
Console.WriteLine(arrayAccessExpr.ToString())

Console.WriteLine("Lambda Expression:")
Console.WriteLine(lambdaExpr.ToString())

Console.WriteLine("The result of executing the lambda expression:")

' The following statement first creates an expression tree, 
' then compiles it, and then executes it. 
' Parameters passed to the Invoke method are passed to the lambda expression.
Console.WriteLine(lambdaExpr.Compile().Invoke(New Integer() {10, 20, 30}, 0, 5))

' This code example produces the following output: 

' Array Access Expression: 
' Array[Index] 

' Lambda Expression: 
' (Array, Index, Value) => (Array[Index] = (Array[Index] + Value)) 

' The result of executing the lambda expression: 
' 15

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, 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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