TryExpression Klass

Definition

public ref class TryExpression sealed : System::Linq::Expressions::Expression

public sealed class TryExpression : System.Linq.Expressions.Expression

type TryExpression = class
    inherit Expression

Public NotInheritable Class TryExpression
Inherits Expression

Arv

Object

Expression

TryExpression

Exempel

I följande exempel visas hur du skapar ett TryExpression objekt som innehåller en catch-instruktion med hjälp TryCatch av metoden.

// Add the following directive to the file:
// using System.Linq.Expressions;

// A TryExpression object that has a Catch statement.
// The return types of the Try block and all Catch blocks must be the same.
TryExpression tryCatchExpr =
    Expression.TryCatch(
        Expression.Block(
            Expression.Throw(Expression.Constant(new DivideByZeroException())),
            Expression.Constant("Try block")
        ),
        Expression.Catch(
            typeof(DivideByZeroException),
            Expression.Constant("Catch block")
        )
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
// If the exception is caught,
// the result of the TryExpression is the last statement
// of the corresponding Catch statement.
Console.WriteLine(Expression.Lambda<Func<string>>(tryCatchExpr).Compile()());

// This code example produces the following output:
//
// Catch block

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

' A TryExpression object that has a Catch statement.
' The return types of the Try block and all Catch blocks must be the same.
Dim tryCatchExpr As TryExpression =
       Expression.TryCatch(
           Expression.Block(
               Expression.Throw(Expression.Constant(New DivideByZeroException())),
               Expression.Constant("Try block")
           ),
           Expression.Catch(
               GetType(DivideByZeroException),
               Expression.Constant("Catch block")
           )
       )

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
' If the exception is caught, 
' the result of the TryExpression is the last statement 
' of the corresponding Catch statement.
Console.WriteLine(Expression.Lambda(Of Func(Of String))(tryCatchExpr).Compile()())

' This code example produces the following output:
'
' Catch block

Kommentarer

Brödtextblocket skyddas av try-blocket.

Hanterarna består av en uppsättning CatchBlock uttryck som kan vara antingen catch-instruktioner eller filter.

Felblocket körs om ett undantag utlöses.

Slutligen körs blocket oavsett hur kontrollen avslutar brödtexten.

Endast ett av fel eller slutligen block kan anges.

Returtypen för try-blocket måste matcha returtypen för associerade catch-instruktioner.