ExceptionHandlingClause Classe

Definição

Namespace:

System.Reflection

Assembly:

System.Runtime.dll

Origem:

ExceptionHandlingClause.cs

Representa uma cláusula em um bloco de tratamento de exceções estruturado.

public ref class ExceptionHandlingClause

public class ExceptionHandlingClause

type ExceptionHandlingClause = class

Public Class ExceptionHandlingClause

Herança

Object

ExceptionHandlingClause

Exemplos

O exemplo de código a seguir define um método de teste chamado MethodBodyExamplee exibe suas informações de variável local e cláusulas de tratamento de exceção. O MethodBase.GetMethodBody método é usado para obter um MethodBody objeto para o método de teste. A ExceptionHandlingClauses propriedade é usada para obter uma lista de ExceptionHandlingClause objetos e exibir suas propriedades.

Você pode usar Ildasm.exe para examinar o MSIL para o exemplo de código compilado, para ver como os deslocamentos e comprimentos são calculados.

Esse código faz parte de um exemplo maior localizado no tópico de MethodBody classe.

#using <System.dll>

using namespace System;
using namespace System::Reflection;

public ref class Example
{
    // The Main method contains code to analyze this method, using
    // the properties and methods of the MethodBody class.
public:
    void MethodBodyExample(Object^ arg)
    {
        // Define some local variables. In addition to these variables,
        // the local variable list includes the variables scoped to 
        // the catch clauses.
        int var1 = 42;
        String^ var2 = "Forty-two";

        try
        {
            // Depending on the input value, throw an ArgumentException or 
            // an ArgumentNullException to test the Catch clauses.
            if (arg == nullptr)
            {
                throw gcnew ArgumentNullException("The argument cannot " +
                    "be null.");
            }
            if (arg->GetType() == String::typeid)
            {
                throw gcnew ArgumentException("The argument cannot " + 
                    "be a string.");
            }        
        }

        // There is no Filter clause in this code example. See the Visual 
        // Basic code for an example of a Filter clause.

        // This catch clause handles the ArgumentException class, and
        // any other class derived from Exception.
        catch (ArgumentException^ ex)
        {
            Console::WriteLine("Ordinary exception-handling clause caught:" +
                " {0}", ex->GetType());
        }        
        finally
        {
            var1 = 3033;
            var2 = "Another string.";
        }
    }
};

int main()
{ 
    // Get method body information.
    MethodInfo^ mi = 
        Example::typeid->GetMethod("MethodBodyExample");

    MethodBody^ mb = mi->GetMethodBody();
    Console::WriteLine("\r\nMethod: {0}", mi);

    // Display the general information included in the 
    // MethodBody object.
    Console::WriteLine("    Local variables are initialized: {0}", 
        mb->InitLocals);
    Console::WriteLine("    Maximum number of items on the operand " +
        "stack: {0}", mb->MaxStackSize);

using System;
using System.Reflection;

public class Example
{
    public static void Main()
    {
        // Get method body information.
        MethodInfo mi = typeof(Example).GetMethod("MethodBodyExample");
        MethodBody mb = mi.GetMethodBody();
        Console.WriteLine("\r\nMethod: {0}", mi);

        // Display the general information included in the
        // MethodBody object.
        Console.WriteLine("    Local variables are initialized: {0}",
            mb.InitLocals);
        Console.WriteLine("    Maximum number of items on the operand stack: {0}",
            mb.MaxStackSize);

Imports System.Reflection

Public Class Example

    Public Shared Sub Main()

        ' Demonstrate the effect of the Visual Basic When keyword, which
        ' generates a Filter clause in the Try block.
        Dim e As New Example()
        Console.WriteLine()
        e.MethodBodyExample("String argument")
        e.MethodBodyExample(Nothing)

        ' Get method body information.
        Dim mi As MethodInfo = _
            GetType(Example).GetMethod("MethodBodyExample")
        Dim mb As MethodBody = mi.GetMethodBody()
        Console.WriteLine(vbCrLf & "Method: {0}", mi)

        ' Display the general information included in the 
        ' MethodBody object.
        Console.WriteLine("    Local variables are initialized: {0}", _
            mb.InitLocals)
        Console.WriteLine("    Maximum number of items on the operand stack: {0}", _
            mb.MaxStackSize)

// Display exception handling clauses.
Console::WriteLine();
for each(ExceptionHandlingClause^ exhc in mb->ExceptionHandlingClauses)
{
    Console::WriteLine(exhc->Flags.ToString());

    // The FilterOffset property is meaningful only for Filter
    // clauses. The CatchType property is not meaningful for 
    // Filter or Finally clauses. 
    switch(exhc->Flags)
    {
    case ExceptionHandlingClauseOptions::Filter:
        Console::WriteLine("        Filter Offset: {0}", 
            exhc->FilterOffset);
        break;
    case ExceptionHandlingClauseOptions::Finally:
        break;
    default:
        Console::WriteLine("    Type of exception: {0}", 
            exhc->CatchType);
        break;
    }

    Console::WriteLine("       Handler Length: {0}",
        exhc->HandlerLength);
    Console::WriteLine("       Handler Offset: {0}", 
        exhc->HandlerOffset);
    Console::WriteLine("     Try Block Length: {0}", exhc->TryLength);
    Console::WriteLine("     Try Block Offset: {0}", exhc->TryOffset);
}

// Display exception handling clauses.
Console.WriteLine();
foreach (ExceptionHandlingClause ehc in mb.ExceptionHandlingClauses)
{
    Console.WriteLine(ehc.Flags.ToString());

    // The FilterOffset property is meaningful only for Filter
    // clauses. The CatchType property is not meaningful for
    // Filter or Finally clauses.
    switch (ehc.Flags)
    {
        case ExceptionHandlingClauseOptions.Filter:
            Console.WriteLine("        Filter Offset: {0}",
                ehc.FilterOffset);
            break;
        case ExceptionHandlingClauseOptions.Finally:
            break;
        default:
            Console.WriteLine("    Type of exception: {0}",
                ehc.CatchType);
            break;
    }

    Console.WriteLine("       Handler Length: {0}", ehc.HandlerLength);
    Console.WriteLine("       Handler Offset: {0}", ehc.HandlerOffset);
    Console.WriteLine("     Try Block Length: {0}", ehc.TryLength);
    Console.WriteLine("     Try Block Offset: {0}", ehc.TryOffset);
}

' Display exception handling clauses.
Console.WriteLine()
For Each ehc As ExceptionHandlingClause In mb.ExceptionHandlingClauses
    Console.WriteLine(ehc.Flags.ToString())

    ' The FilterOffset property is meaningful only for Filter
    ' clauses. The CatchType property is not meaningful for 
    ' Filter or Finally clauses. 
    Select Case ehc.Flags
        Case ExceptionHandlingClauseOptions.Filter
            Console.WriteLine("        Filter Offset: {0}", _
                ehc.FilterOffset)
        Case ExceptionHandlingClauseOptions.Finally
        Case Else
            Console.WriteLine("    Type of exception: {0}", _
                ehc.CatchType)
    End Select

    Console.WriteLine("       Handler Length: {0}", ehc.HandlerLength)
    Console.WriteLine("       Handler Offset: {0}", ehc.HandlerOffset)
    Console.WriteLine("     Try Block Length: {0}", ehc.TryLength)
    Console.WriteLine("     Try Block Offset: {0}", ehc.TryOffset)
Next

    // The Main method contains code to analyze this method, using
    // the properties and methods of the MethodBody class.
public:
    void MethodBodyExample(Object^ arg)
    {
        // Define some local variables. In addition to these variables,
        // the local variable list includes the variables scoped to 
        // the catch clauses.
        int var1 = 42;
        String^ var2 = "Forty-two";

        try
        {
            // Depending on the input value, throw an ArgumentException or 
            // an ArgumentNullException to test the Catch clauses.
            if (arg == nullptr)
            {
                throw gcnew ArgumentNullException("The argument cannot " +
                    "be null.");
            }
            if (arg->GetType() == String::typeid)
            {
                throw gcnew ArgumentException("The argument cannot " + 
                    "be a string.");
            }        
        }

        // There is no Filter clause in this code example. See the Visual 
        // Basic code for an example of a Filter clause.

        // This catch clause handles the ArgumentException class, and
        // any other class derived from Exception.
        catch (ArgumentException^ ex)
        {
            Console::WriteLine("Ordinary exception-handling clause caught:" +
                " {0}", ex->GetType());
        }        
        finally
        {
            var1 = 3033;
            var2 = "Another string.";
        }
    }

    }

    // The Main method contains code to analyze this method, using
    // the properties and methods of the MethodBody class.
    public void MethodBodyExample(object arg)
    {
        // Define some local variables. In addition to these variables,
        // the local variable list includes the variables scoped to
        // the catch clauses.
        int var1 = 42;
        string var2 = "Forty-two";

        try
        {
            // Depending on the input value, throw an ArgumentException or
            // an ArgumentNullException to test the Catch clauses.
            if (arg == null)
            {
                throw new ArgumentNullException("The argument cannot be null.");
            }
            if (arg.GetType() == typeof(string))
            {
                throw new ArgumentException("The argument cannot be a string.");
            }
        }

        // This filter clause selects only exceptions that derive
        // from the ArgumentException class.
        // Other exceptions, including ArgumentException itself,
        // are not handled by this filter clause.
        catch (ArgumentException ex) when (ex.GetType().IsSubclassOf(typeof(ArgumentException)))
        {
            Console.WriteLine("Filter clause caught: {0}", ex.GetType());
        }

        // This catch clause handles the ArgumentException class, and
        // any other class derived from Exception.
        catch(Exception ex)
        {
            Console.WriteLine("Ordinary exception-handling clause caught: {0}",
                ex.GetType());
        }
        finally
        {
            var1 = 3033;
            var2 = "Another string.";
        }
    }
}

// This code example produces output similar to the following:
//
//Method: Void MethodBodyExample(System.Object)
//    Local variables are initialized: True
//    Maximum number of items on the operand stack: 2

    End Sub

    ' This test method is executed at the beginning of Main, to show
    ' how the Filter clause works. The Filter clause is generated by 
    ' a Visual Basic When expression. If arg is Nothing, this method
    ' throws ArgumentNullException, which is caught by the filter
    ' clause. If arg is a string, the method throws ArgumentException,
    ' which does not match the filter clause.
    '
    ' Sub Main also contains code to analyze this method, using 
    ' the properties and methods of the MethodBody class.
    Public Sub MethodBodyExample(ByVal arg As Object)

        ' Define some local variables. In addition to these variables,
        ' the local variable list includes the variables scoped to 
        ' the catch clauses.
        Dim var1 As Integer = 42
        Dim var2 As String = "Forty-two"

        Try
            ' Depending on the input value, throw an ArgumentException or 
            ' an ArgumentNullException to test the Catch clauses.
            '
            If arg Is Nothing Then
                Throw New ArgumentNullException("The argument cannot be Nothing.")
            End If
            If arg.GetType() Is GetType(String) Then
                Throw New ArgumentException("The argument cannot be a string.")
            End If
        
        ' The When expression makes this a filter clause. The expression 
        ' selects only exceptions that derive from the ArgumentException
        ' class. Other exceptions, including ArgumentException itself, 
        ' are not handled by this filter clause.
        Catch ex As ArgumentException _
            When ex.GetType().IsSubclassOf(GetType(ArgumentException))

            Console.WriteLine("Filter clause caught: {0}", ex.GetType())
        
        ' This catch clause handles the ArgumentException class, and
        ' any other class derived from Exception.
        Catch ex As Exception
            Console.WriteLine("Ordinary exception-handling clause caught: {0}", _
                ex.GetType())

        Finally
            var1 = 3033
            var2 = "Another string."
        End Try
    End Sub
End Class

' This code example produces output similar to the following:
'
'Ordinary exception-handling clause caught: System.ArgumentException
'Filter clause caught: System.ArgumentNullException
'
'Method: Void MethodBodyExample(System.Object)
'    Local variables are initialized: True
'    Maximum number of items on the operand stack: 3

//Clause
//    Type of exception: System.ArgumentException
//       Handler Length: 29
//       Handler Offset: 78
//     Try Block Length: 65
//     Try Block Offset: 13
//Finally
//       Handler Length: 13
//       Handler Offset: 113
//     Try Block Length: 100
//     Try Block Offset: 13

//
//Filter
//      Filter Offset: 71
//      Handler Length: 23
//      Handler Offset: 116
//      Try Block Length: 61
//      Try Block Offset: 10
//Clause
//    Type of exception: System.Exception
//       Handler Length: 21
//       Handler Offset: 70
//     Try Block Length: 61
//     Try Block Offset: 9
//Finally
//       Handler Length: 14
//       Handler Offset: 94
//     Try Block Length: 85
//     Try Block Offset: 9

'
'Filter
'        Filter Offset: 0
'       Handler Length: 19
'       Handler Offset: 99
'     Try Block Length: 45
'     Try Block Offset: 9
'Clause
'    Type of exception: System.Exception
'       Handler Length: 25
'       Handler Offset: 118
'     Try Block Length: 45
'     Try Block Offset: 9
'Finally
'       Handler Length: 13
'       Handler Offset: 153
'     Try Block Length: 144
'     Try Block Offset: 9

Comentários

A ExceptionHandlingClause classe fornece informações sobre as cláusulas em um try...catch... finally bloco (Try...Catch...Finally no Visual Basic). Para obter uma lista de cláusulas de tratamento de exceção em um método , obtenha um MethodInfo que representa o método . Use o GetMethodBody método para obter um MethodBody objeto e, em seguida, use a ExceptionHandlingClauses propriedade para obter a lista de cláusulas.

Observação

Trabalhar com cláusulas de tratamento de exceções requer uma compreensão completa dos metadados e dos formatos de instrução msil (microsoft intermediate language). As informações podem ser encontradas na documentação da CLI (Common Language Infrastructure), especialmente "Partição II: Definição e Semântica de Metadados".

Construtores

ExceptionHandlingClause()

Inicializa uma nova instância da classe ExceptionHandlingClause.

Propriedades

CatchType	Obtém o tipo da exceção tratada por essa cláusula.
FilterOffset	Obtém o deslocamento dentro do corpo do método, em bytes, do código do filtro fornecido pelo usuário.
Flags	Obtém um valor que indica se esta cláusula de manipulação de exceção é uma cláusula finally, uma cláusula filtrada por tipo ou uma cláusula filtrada por usuário.
HandlerLength	Obtém o comprimento, em bytes, do corpo dessa cláusula de tratamento de exceção.
HandlerOffset	Obtém o deslocamento dentro do corpo do método, em bytes, dessa cláusula de tratamento de exceção.
TryLength	O comprimento total, em bytes, do bloco try que inclui a cláusula de tratamento de exceção.
TryOffset	O deslocamento no método, em bytes, do bloco try que inclui a cláusula de tratamento de exceção.

Métodos

Equals(Object)	Determina se o objeto especificado é igual ao objeto atual. (Herdado de Object)
GetHashCode()	Serve como a função de hash padrão. (Herdado de Object)
GetType()	Obtém o Type da instância atual. (Herdado de Object)
MemberwiseClone()	Cria uma cópia superficial do Object atual. (Herdado de Object)
ToString()	Uma representação de cadeia de caracteres da cláusula de tratamento de exceção.

Confira também

• MethodBody
• ExceptionHandlingClauses
• ExceptionHandlingClauseOptions