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 Do not catch general exception type...

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This page is specific to
Microsoft Visual Studio 2005/.Net Framework 2.0

Other versions are also available for the following:
Visual Studio Team System
Do not catch general exception types

TypeName

DoNotCatchGeneralExceptionTypes

CheckId

CA1031

Category

Microsoft.Design

Breaking Change

NonBreaking

System.Exception or System.SystemException is caught in a catch statement, or a general catch clause is used.

General exceptions should not be caught.

To fix a violation of this rule, catch a more specific exception, or re-throw the general exception as the last statement in the catch block.

Do not exclude a warning from this rule. Catching general exception types can hide run-time problems from the library user, and can complicate debugging.

The following example shows a type that violates this rule and a type that correctly implements the catch block.

Visual Basic
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
C#
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;
            }
        }
    }
}
C++
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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FAQ: Why does FxCop warn against catch(Exception)?      David M. Kean   |   Edit   |   Show History

See the following post on the Visual Studio Code Analysis blog:
http://blogs.msdn.com/fxcop/archive/2006/06/14/631923.aspx

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