Artikel
11/18/2011

Expression.TryCatchFinally 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 a finally block.

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

Syntax

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

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

Parameters

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

finally
Type: System.Linq.Expressions.Expression
The body of the finally 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 and a finally statement.

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

        ' A TryExpression object that has a catch statement and a finally statement.
        ' The return types of the try block and all catch blocks must be the same.
        Dim tryCatchExpr As TryExpression =
            Expression.TryCatchFinally(
                Expression.Block(
                    Expression.Throw(Expression.Constant(New DivideByZeroException())),
                    Expression.Constant("Try block")
                 ),
            Expression.Call(
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("Finally 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:
        '
        ' Finally block
        ' Catch block

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

// A TryExpression object that has a catch statement and a finally statement.
// The return types of the try block and all catch blocks must be the same.
TryExpression tryCatchExpr =
    Expression.TryCatchFinally(
        Expression.Block(
            Expression.Throw(Expression.Constant(new DivideByZeroException())),
            Expression.Constant("Try block")
        ),
        Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }), Expression.Constant("Finally 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:
//
// Finally block
// 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.

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