The exception information table represents four types of exception handlers for protected blocks:
- A finally handler that executes whenever the block exits, whether that occurs by normal control flow or by an unhandled exception.
- A fault handler that must execute if an exception occurs, but does not execute on completion of normal control flow.
- A type-filtered handler that handles any exception of a specified class or any of its derived classes.
- A user-filtered handler that runs user-specified code to determine whether the exception should be handled by the associated handler or should be passed to the next protected block.
The runtime uses an exception handling model based on exception objects and protected blocks of code. An Exception object is created to represent an exception when it occurs.
The runtime creates an exception information table for each executable. Each method of the executable has an associated array of exception handling information (which can be empty) in the exception information table. Each entry in the array describes a protected block of code, any exception filters associated with that code, and any exception handlers (catch statements). This exception table is extremely efficient and there is no performance penalty in processor time or in memory use when an exception does not occur. You use resources only when an exception occurs.
We code to make the program perfect and Error free; eventhough there is a chance of errors. All .NET Framework operations indicate failure by throwing exceptions.
An exception is any error condition or unexpected behavior encountered by an executing program. Exceptions can be raised because of a fault in your code or in code you call (such as a shared library), unavailable operating system resources, unexpected conditions the common language runtime encounters (such as code that cannot be verified), and so on.
In the .NET Framework, an exception is an object that inherits from the Exception Class class. An exception is thrown from an area of code where a problem has occurred. The exception is passed up the stack until the application handles it or the program terminates.
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