Allgemeine Ausnahmetypen nicht auffangen

Aktualisiert: November 2007

Ursache

System.Exception oder System.SystemException wird in einer catch-Anweisung abgefangen, oder es wird eine allgemeine catch-Klausel verwendet.

Regelbeschreibung

Allgemeine Ausnahmen sollten nicht abgefangen werden.

Behandlung von Verstößen

Um einen Verstoß gegen diese Regel zu beheben, fangen Sie eine spezifischere Ausnahme ab oder lösen die allgemeine Ausnahme in der letzten Anweisung des catch-Blocks erneut aus.

Wann sollten Warnungen unterdrückt werden?

Unterdrücken Sie keine Warnung dieser Regel. Durch das Abfangen allgemeiner Ausnahmetypen können Laufzeitprobleme vor dem Bibliotheksbenutzer verborgen werden und das Debuggen kann komplizierter werden.

Beispiel

Im folgenden Beispiel werden ein Typ, der gegen diese Regel verstößt, und ein Typ veranschaulicht, in dem der catch-Block korrekt implementiert wurde.

Imports System
Imports System.IO

Namespace DesignLibrary

    ' Creates two violations of the rule.
    Public Class GenericExceptionsCaught

        Dim inStream  As FileStream 
        Dim outStream As FileStream 

        Sub New(inFile As String, outFile As String)

            Try
                inStream = File.Open(inFile, FileMode.Open)
            Catch ex As SystemException
                Console.WriteLine("Unable to open {0}.", inFile)
            End Try

            Try
                outStream = File.Open(outFile, FileMode.Open)
            Catch
                Console.WriteLine("Unable to open {0}.", outFile)
            End Try

        End Sub

    End Class

    Public Class GenericExceptionsCaughtFixed

        Dim inStream  As FileStream 
        Dim outStream As FileStream 

        Sub New(inFile As String, outFile As String)

            Try
                inStream = File.Open(inFile, FileMode.Open)

            ' Fix the first violation by catching a specific exception.
            Catch ex As FileNotFoundException
                Console.WriteLine("Unable to open {0}.", inFile)
            End Try

            Try
                outStream = File.Open(outFile, FileMode.Open)

            ' Fix the second violation by re-throwing the generic 
            ' exception at the end of the catch block.
            Catch
                Console.WriteLine("Unable to open {0}.", inFile)
            Throw
            End Try

        End Sub

    End Class

End Namespace

using System;
using System.IO;

namespace DesignLibrary
{
    // Creates two violations of the rule.
    public class GenericExceptionsCaught
    {
        FileStream inStream;
        FileStream outStream;

        public GenericExceptionsCaught(string inFile, string outFile)
        {
            try
            {
                inStream = File.Open(inFile, FileMode.Open);
            }
            catch(SystemException e)
            {
                Console.WriteLine("Unable to open {0}.", inFile);
            }

            try
            {
                outStream = File.Open(outFile, FileMode.Open);
            }
            catch
            {
                Console.WriteLine("Unable to open {0}.", outFile);
            }
        }
    }

    public class GenericExceptionsCaughtFixed
    {
        FileStream inStream;
        FileStream outStream;

        public GenericExceptionsCaughtFixed(string inFile, string outFile)
        {
            try
            {
                inStream = File.Open(inFile, FileMode.Open);
            }

            // Fix the first violation by catching a specific exception.
            catch(FileNotFoundException e)
            {
                Console.WriteLine("Unable to open {0}.", inFile);
            }

            try
            {
                outStream = File.Open(outFile, FileMode.Open);
            }

            // Fix the second violation by re-throwing the generic 
            // exception at the end of the catch block.
            catch
            {
                Console.WriteLine("Unable to open {0}.", outFile);
                throw;
            }
        }
    }
}

using namespace System;
using namespace System::IO;

namespace DesignLibrary
{
    // Creates two violations of the rule.
    public ref class GenericExceptionsCaught
    {
        FileStream^ inStream;
        FileStream^ outStream;

    public:
        GenericExceptionsCaught(String^ inFile, String^ outFile)
        {
            try
            {
                inStream = File::Open(inFile, FileMode::Open);
            }
            catch(SystemException^ e)
            {
                Console::WriteLine("Unable to open {0}.", inFile);
            }

            try
            {
                outStream = File::Open(outFile, FileMode::Open);
            }
            catch(Exception^ e)
            {
                Console::WriteLine("Unable to open {0}.", outFile);
            }
        }
    };

    public ref class GenericExceptionsCaughtFixed
    {
        FileStream^ inStream;
        FileStream^ outStream;

    public:
        GenericExceptionsCaughtFixed(String^ inFile, String^ outFile)
        {
            try
            {
                inStream = File::Open(inFile, FileMode::Open);
            }

            // Fix the first violation by catching a specific exception.
            catch(FileNotFoundException^ e)
            {
                Console::WriteLine("Unable to open {0}.", inFile);
            }

            try
            {
                outStream = File::Open(outFile, FileMode::Open);
            }

            // Fix the second violation by re-throwing the generic 
            // exception at the end of the catch block.
            catch(Exception^ e)
            {
                Console::WriteLine("Unable to open {0}.", outFile);
                throw;
            }
        }
    };
}

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