CA1031: Do not catch general exception types
TypeName |
DoNotCatchGeneralExceptionTypes |
CheckId |
CA1031 |
Category |
Microsoft.Design |
Breaking Change |
Non-breaking |
Cause
A general exception such as System.Exception or System.SystemException is caught in a catch statement, or a general catch clause such as catch() is used.
Rule Description
General exceptions should not be caught.
How to Fix Violations
To fix a violation of this rule, catch a more specific exception, or rethrow the general exception as the last statement in the catch block.
When to Suppress Warnings
Do not suppress a warning from this rule. Catching general exception types can hide run-time problems from the library user and can make debugging more difficult.
Note
Starting with the .NET Framework 4, the common language runtime (CLR) no longer delivers corrupted state exceptions that occur in the operating system and managed code, such as access violations in Windows, to be handled by managed code. If you want to compile an application in the .NET Framework 4 or later versions and maintain handling of corrupted state exceptions, you can apply the HandleProcessCorruptedStateExceptionsAttribute attribute to the method that handles the corrupted state exception.
Example
The following example shows a type that violates this rule and a type that correctly implements the catch block.
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}.", outFile)
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;
}
}
};
}