Expression.TryCatchFinally(Expression, Expression, CatchBlock[]) Metod

Definition

Namnområde:
System.Linq.Expressions
Sammansättningar:
System.Core.dll, System.Linq.Expressions.dll
Sammansättning:
System.Core.dll
Sammansättning:
System.Linq.Expressions.dll
Sammansättning:
netstandard.dll

Skapar ett TryExpression som representerar ett försöksblock med valfritt antal catch-instruktioner och ett slutligen block.

public:
 static System::Linq::Expressions::TryExpression ^ TryCatchFinally(System::Linq::Expressions::Expression ^ body, System::Linq::Expressions::Expression ^ finally, ... cli::array <System::Linq::Expressions::CatchBlock ^> ^ handlers);
public static System.Linq.Expressions.TryExpression TryCatchFinally(System.Linq.Expressions.Expression body, System.Linq.Expressions.Expression finally, params System.Linq.Expressions.CatchBlock[] handlers);
static member TryCatchFinally : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Linq.Expressions.CatchBlock[] -> System.Linq.Expressions.TryExpression
Public Shared Function TryCatchFinally (body As Expression, finally As Expression, ParamArray handlers As CatchBlock()) As TryExpression

Parametrar

body
Expression

Brödtexten i try-blocket.

finally
Expression

Brödtexten i det sista blocket.

handlers
CatchBlock[]

Matrisen med noll eller fler CatchBlock uttryck som representerar de catch-uttryck som ska associeras med try-blocket.

Returer

TryExpression

Den skapade TryExpression.

Exempel

I följande exempel visas hur du skapar ett TryExpression objekt som innehåller en catch-instruktion och en slutsats.

// 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.
Console.WriteLine(Expression.Lambda<Func<string>>(tryCatchExpr).Compile()());

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

' 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.
Console.WriteLine(Expression.Lambda(Of Func(Of String))(tryCatchExpr).Compile()())

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

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