TryExpression Sınıf

Tanım

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

Devralma

Object

Expression

TryExpression

Örnekler

Aşağıdaki örnekte yöntemini kullanarak catch deyimi içeren bir TryExpression nesnenin nasıl oluşturulacağı gösterilmektedir TryCatch .

// 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

Açıklamalar

Gövde bloğu try bloğu tarafından korunur.

İşleyiciler, catch deyimleri veya filtreler olabilecek bir CatchBlock dizi ifadeden oluşur.

Bir özel durum oluşursa hata bloğu çalışır.

Son blok, denetimin gövdeden nasıl çıktığına bakılmaksızın çalışır.

Yalnızca bir hata veya son blok sağlanabilir.

Try bloğunun dönüş türü, ilişkili catch deyimlerinin dönüş türüyle eşleşmelidir.

Özellikler

Yöntemler

Şunlara uygulanır