Expression.TryCatch(Expression, CatchBlock[]) 方法

定义

命名空间:

System.Linq.Expressions

程序集:

System.Linq.Expressions.dll

Source:

TryExpression.cs

创建一个表示 try 块的 TryExpression，该 try 块包含任意数量的 catch 语句，但不包含 fault 和 finally 块。

public:
 static System::Linq::Expressions::TryExpression ^ TryCatch(System::Linq::Expressions::Expression ^ body, ... cli::array <System::Linq::Expressions::CatchBlock ^> ^ handlers);

public static System.Linq.Expressions.TryExpression TryCatch (System.Linq.Expressions.Expression body, params System.Linq.Expressions.CatchBlock[]? handlers);

static member TryCatch : System.Linq.Expressions.Expression * System.Linq.Expressions.CatchBlock[] -> System.Linq.Expressions.TryExpression

Public Shared Function TryCatch (body As Expression, ParamArray handlers As CatchBlock()) As TryExpression

参数

body

Expression

try 块的主体。

handlers

CatchBlock[]

包含零个或多个 CatchBlock 表达式的数组，这些表达式表示要与 try 块关联的 catch 语句。

返回

TryExpression

创建的 TryExpression。

示例

以下示例演示如何创建 TryExpression 包含 catch 语句的对象。

// 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