Expression.Block Method (Expression())

 

Creates a BlockExpression that contains the given expressions and has no variables.

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

Public Shared Function Block (
	ParamArray expressions As Expression()
) As BlockExpression

Parameters

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

The expressions in the block.

When the block expression is executed, it returns the value of the last expression in the block.

The following code example shows how to create a block expression. The block expression consists of two MethodCallExpression objects and one ConstantExpression object.

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

' The block expression enables you to execute several expressions sequentually.
' When the block expression is executed,
' it returns the value of the last expression in the sequence.
Dim blockExpr As BlockExpression = Expression.Block(
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("Write", New Type() {GetType(String)}),
        Expression.Constant("Hello ")
       ),
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
        Expression.Constant("World!")
        ),
    Expression.Constant(42)
)

Console.WriteLine("The result of executing the expression tree:")
' The following statement first creates an expression tree,
' then compiles it, and then executes it.           
Dim result = Expression.Lambda(Of Func(Of Integer))(blockExpr).Compile()()

' Print the expressions from the block expression.
Console.WriteLine("The expressions from the block expression:")
For Each expr In blockExpr.Expressions
    Console.WriteLine(expr.ToString())
Next

' Print the result of the tree execution.
Console.WriteLine("The return value of the block expression:")
Console.WriteLine(result)

' This code example produces the following output:
'
' The result of executing the expression tree:
' Hello World!

' The expressions from the block expression:
' Write("Hello ")
' WriteLine("World!")
' 42

' The return value of the block expression:
' 42

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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