引发异常时Catch Block的行为

Question

Is there any case where catch block is skipped when an Exception is raised say

try 
{
  some code
}
catch(Exception ex)
{
  some code
}

I am using Exception class as it catches all the Exceptions.

Answer 1

You might have problems with StackOverflowException (see List of exceptions that CAN'T be caught in .NET )

There is another family of cases, specifically when the thing thrown wasn't an Exception , but this is only if you are either in 1.1, or don't have automatic exception wrapping enabled (it is enabled by default from 2.0) - it is theoretically possible for C++ to throw anything (not just an Exception ), so if your "some code" calls into some C++ that throws, say, a string , then in theory you could miss it.

In reality this is rarely (if ever) a real problem:

• the automatic wrapping is enabled by default
• most C++ code talking to .NET throws Exception (or a subclass) to be well-behaved

In such cases, a catch { ... } will work to intercept that something was thrown, but won't tell you what happened.

Answer 2

All exceptions have Exception as base type. If the code in the try block causes an exception, it will cause the code in the catch block of matching type to be executed. If you also have a more specific catch block that matches, that block will be executed:

try
{
    throw new FileNotFoundException();
}
catch (FileNotFoundException)
{
    // this code will run
}
catch (Exception)
{
    // this won't (but will if a different exception is thrown)
}

If the code in the catch block causes an Exception , it will leave the catch block and find a "parent" catch block that matches.

Note that only exceptions on the current thread are caught - if you start and wait for asynchronous operations within the try block, you may not catch them on the waiting thread.

Answer 3

As Marc has pointed out there are few exceptions that cannot be caught - for example, StackOverflowException.

With .NET 4, there is concept of Corrupted State Exceptions to indicate exceptions that are not delivered to managed code unless code has explicitly indicated an interest in handling them. These exceptions (eg AccessVoilationException) indicates serious programming error and in general, does not guarantee the consistent memory/program state when occurred. See this excellent article for more information: http://msdn.microsoft.com/en-us/magazine/dd419661.aspx

Answer 4

If there is an exception with the CLR (such as stack overflow) - it will not catch that Exception.

But for normal exceptions, you'll catch everything.

Answer 5

It shouldn't skip as all exceptions are derived from Exception class. Did you have any kind of occasion where it happened the other way?

Answer 6

try  
{   
    //some code 
} 
catch(System.DivideByZeroException dbz)
{
    //Divide by Zero exception catched
}
catch(Exception ex) 
{   
    //some code 
} 

You have given Exception class which is the base class for all exception. So you need to give specific Exception class like ArgumentNotFound Exception.

If you dont want to catch any Exception just leave it blank. But keep one thing in mind, using Try..Catch Block use high resource, so it is advisable to use it only if you are sure what kind of exception may occur.