Článek
11/18/2011

Expression.TryCatch Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Creates a TryExpression representing a try block with any number of catch statements and neither a fault nor finally block.

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

Syntax

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

public static TryExpression TryCatch(
    Expression body,
    params CatchBlock[] handlers
)

Parameters

body
Type: System.Linq.Expressions.Expression
The body of the try block.

handlers
Type: array<System.Linq.Expressions.CatchBlock[]
The array of zero or more CatchBlock expressions representing the catch statements to be associated with the try block.

Return Value

Type: System.Linq.Expressions.TryExpression
The created TryExpression.

Examples

The following example demonstrates how to create a TryExpression object that contains a catch statement.

' 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.
outputBlock.Text &= Expression.Lambda(Of Func(Of String))(tryCatchExpr).Compile()() & vbCrLf

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

// 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.
outputBlock.Text += Expression.Lambda<Func<string>>(tryCatchExpr).Compile()() + "\n";

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

Version Information

Silverlight

Supported in: 5, 4

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Sdílet prostřednictvím