TRY....CATCH....FINALLY
An exception is a problem that arises during the execution of a program. An exception is a response to an exceptional circumstance that arises while a program is running, such as an attempt to divide by zero.
VB.Net exception handling is built upon four keywords - Try, Catch, Finally and Throw.
- Try − A Try block identifies a block of code for which particular exceptions will be activated. It's followed by one or more Catch blocks.
- Catch − A program catches an exception with an exception handler at the place in a program where you want to handle the problem. The Catch keyword indicates the catching of an exception.
- Finally − The Finally block is used to execute a given set of statements, whether an exception is thrown or not thrown. For example, if you open a file, it must be closed whether an exception is raised or not.
- Throw − A program throws an exception when a problem shows up. This is done using a Throw keyword.
Assuming a block will raise an exception, a method catches an exception using a combination of the Try and Catch keywords. A Try/Catch block is placed around the code that might generate an exception. Code within a Try/Catch block is referred to as protected code.
Syntax:
Try
[ tryStatements ]
Catch [ exception [ As type ] ]
[ catchStatements ]
[ Finally
[ finallyStatements ] ]
End Try
Example:
Dim result As Integer
Try
result = num1 \ num2
Catch e As DivideByZeroException
Console.WriteLine("Exception caught: {0}", e)
Finally
Console.WriteLine("Result: {0}", result)
End Try