本文整理匯總了VB.NET中System.Linq.Expressions.Expression.Block方法的典型用法代碼示例。如果您正苦於以下問題：VB.NET Expression.Block方法的具體用法？VB.NET Expression.Block怎麽用？VB.NET Expression.Block使用的例子？那麽, 這裏精選的方法代碼示例或許可以為您提供幫助。您也可以進一步了解該方法所在類System.Linq.Expressions.Expression的用法示例。
在下文中一共展示了Expression.Block方法的2個代碼示例，這些例子默認根據受歡迎程度排序。您可以為喜歡或者感覺有用的代碼點讚，您的評價將有助於係統推薦出更棒的VB.NET代碼示例。
示例1: ParameterExpression
' Add the following directive to your file:
' Imports System.Linq.Expressions
' This block has a parameter expression
' that represents a variable within the block scope.
' It assigns a value to the variable,
' and then adds a constant to the assigned value.
Dim varExpr As ParameterExpression = Expression.Variable(GetType(Integer), "sampleVar")
Dim blockExpr As BlockExpression = Expression.Block(
New ParameterExpression() {varExpr},
Expression.Assign(varExpr, Expression.Constant(1)),
Expression.Add(varExpr, Expression.Constant(5))
)
' 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
Console.WriteLine("The result of executing the expression tree:")
' The following statement first creates an expression tree,
' then compiles it, and then executes it.
Console.WriteLine(
Expression.Lambda(Of Func(Of Integer))(blockExpr).Compile()())輸出：
The expressions from the block expression: (sampleVar = 1) (sampleVar + 5) The result of executing the expression tree: 6
示例2: GetType
' 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)輸出：
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