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Catch ex As ExceptionType ' Handle Exception of a specified type (i.e. DivideByZeroException, OverflowException, etc.) Catch ex As Exception ' Handle Exception (catch all exceptions of a type not previously specified) Catch ' Handles anything that might be thrown, including non-CLR exceptions.
In computer programming, several language mechanisms exist for exception handling. The term exception is typically used to denote a data structure storing information about an exceptional condition. One mechanism to transfer control, or raise an exception, is known as a throw; the exception is said to be thrown. Execution is transferred to a catch.
In this C# example, all exceptions are caught regardless of type, and a new generic exception is thrown, keeping only the message of the original exception. The original stacktrace is lost, along with the type of the original exception, any exception for which the original exception was a wrapper, and any other information captured in the ...
The first hardware exception handling was found in the UNIVAC I from 1951. Arithmetic overflow executed two instructions at address 0 which could transfer control or fix up the result. [16] Software exception handling developed in the 1960s and 1970s. Exception handling was subsequently widely adopted by many programming languages from the ...
In a language that supports formal exception handling, a graceful exit may be the final step in the handling of an exception. In other languages graceful exits can be implemented with additional statements at the locations of possible errors.
In Object Pascal, D, Java, C#, and Python a finally clause can be added to the try construct. No matter how control leaves the try the code inside the finally clause is guaranteed to execute. This is useful when writing code that must relinquish an expensive resource (such as an opened file or a database connection) when finished processing:
In Java—and similar languages modeled after it, like JavaScript—it is possible to execute code even after return statement, because the finally block of a try-catch structure is always executed. So if the return statement is placed somewhere within try or catch blocks the code within finally (if added) will be executed. It is even possible ...
However, throwing and catching an exception inside a function can be extraordinarily inefficient in some languages; a prime example is Objective-C, where a goto is a much faster alternative. [ 37 ] Another use of goto statements is to modify poorly factored legacy code , where avoiding a goto would require extensive refactoring or code ...