Custom Exceptions in VB.NET

By: Rajesh P.S.

Visual Basic .NET introduces structured exception handling, which offers a powerful and more readable alternative to the "On Error Goto" error handling mechanism found in previous versions of Microsoft Visual Basic.

With structured exception handling in VB.NET, developers can effectively handle exceptions that may occur during program execution. Exceptions are irregular circumstances or errors that can disrupt the normal flow of execution, such as running out of memory, encountering a file that cannot be opened, or attempting an illegal cast operation.

Try-Catch-Finally blocks

In VB.NET, developers have the ability to handle exceptions with ease. They can use structured exception handling constructs like Try-Catch-Finally blocks to catch and handle specific exceptions. This provides a more structured and controlled approach to error handling, enabling developers to handle exceptions and take appropriate action to recover from errors.

Try your code block Catch ex As Exception exception handling block Finally final cleanup block End Try

Furthermore, VB.NET allows developers to create their own custom exceptions. This enables them to define and throw exceptions that are specific to their application's needs or unique circumstances. Custom exceptions can encapsulate specific errors or exceptional situations, providing meaningful information to the calling code or allowing for specific handling logic.

Within their code, developers can also use the keyword "Throw" to deliberately throw an exception. This allows them to raise exceptions based on specific conditions or events within their application, providing a way to communicate and respond to exceptional situations programmatically.

The following VB.NET program shows, how to create a custom exception class and how it is using in the program.

Full Source VB.NET

Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Try Dim i As Integer Dim j As Integer Dim k As Integer j = 10 k = 0 i = j / k Catch ex As Exception Throw (New MyCustomException("You can not divide a number by zeo")) End Try End Sub End Class Public Class MyCustomException Inherits System.ApplicationException Public Sub New(ByVal message As String) MyBase.New(message) MsgBox(message) End Sub End Class

Conclusion

Using structured exception handling in VB.NET and taking advantage of custom exceptions, developers can enhance the reliability, maintainability, and robustness of their applications. The ability to handle exceptions effectively and create custom exceptions provides more control and flexibility in handling irregular circumstances and errors within the application logic.

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