Error Handling Techniques Vb
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Visual Basic .NET Error Handling in Visual Basic .NET ADO.NET for the ADO Programmer Building an N-Tier Application in .NET Calling a .NET Component from a COM Component Calling COM Components from .NET Clients visual basic error handling Common .NET Libraries for Developers Comparing System.Xml in Visual Studio .NET to Microsoft.XMLDOM in Visual Studio 6.0 Converting ASP to ASP.NET Creating Classes in Visual Basic .NET Creating Components in .NET Creating a Windows Form User Control Data Binding with Windows Forms and ADO.NET Designing a .NET Application Designing for Web or Desktop? Determining When to Use Windows Installer Versus XCOPY Differences Between Visual Basic 6.0 and .NET Controls Distributed visual basic 6 error handling Transactions in Visual Basic .NET Error Handling in Visual Basic .NET Getting Started with Windows Forms Inheritance and Interfaces Inheritance from a Base Class in Microsoft .NET Interacting with Message Queues Introduction to ASP.NET and Web Forms Introduction to Visual Studio .NET Managing Versions of an Application Migrating from the SOAP Toolkit to Web Services Overloading Methods in Visual Basic .NET Performing Drag-and-Drop Operations Raising Events and Responding to Events Replacing API Calls with .NET Framework Classes Structuring a .NET Application For Easy Deployment Understanding and Using Assemblies and Namespaces in .NET Using ActiveX Controls with Windows Forms in Visual Studio .NET Using ADO.NET Using COM+ Services in .NET Using Web Services Instead of DCOM Variable and Method Scope in Microsoft .NET Working with MDI Applications and Creating Menus TOC Collapse the table of content Expand the table of content This documentation is archived and is not being maintained. This documentation is archived and is not being maintained. Error Handling in Visual Basic .NET Ken Getz MCW Technologies February 2002 Summary: Discusses how error handling differs between Visual Basic .NET and Visual Basic 6.0. Main topics include Try/Catch blocks, Exception objects, procedure callers, and how to create your own Exception classes. (17 printed pages) Objectives Compare er
Database Guide User login Username: * Password: * Request new password Home › Tutorials Error Handling In Visual Basic Level: Despite your best efforts to cover all possible contingencies, run-time errors will occur in your applications. You can and should do all
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you can to prevent them, but when they happen you have to handle them. Introduction c++ error handling Trapping Errors at Run-Time Building Error Handlers Raising Your Own Errors Summary Introduction The various functions, statements, properties and methods available in Visual
Vba Error Handling
Basic and the components used in Visual Basic expect to deal with certain types of data and behavior in your applications. For example, the CDate() function can convert a value to a Date variable. The function is remarkably https://msdn.microsoft.com/en-us/library/ms973849.aspx flexible in the type of information it can accept, but it expects to receive data that it can use to derive a date. If you provide input that it can't convert, it raises error number 13 - "Type mismatch" - essentially saying "I can't handle this input data." In an application, this type of error may be a program logic error (you simply passed the wrong data) or it may be a data entry error on http://www.vb6.us/tutorials/error-handling the part of the user (you asked for a date and the user typed a name). In the first case, you need to debug the program to fix the mistake. However, there is no way for you to anticipate the behavior of the end users of the application. If the user enters data you can't handle, you need to deal with the situation. Dealing with errors at run-time is a two step process: Trap the Error Before you can deal with an error, you need to know about it. You use VB's On Error statement to setup an error trap. Handle the Error Code in your error handler may correct an error, ignore it, inform the user of the problem, or deal with it in some other way. You can examine the properties of the Err object to determine the nature of the error. Once the error has been dealt with, you use the Resume statement to return control to the regular flow of the code in the application. In addition to dealing with run-time errors, you may at times want to generate them. This is often done in class modules built as components of ActiveX server DLLs or EXEs. It is considered good programming practice to separate the user interface from the program logic as much as possible, so if a server component cannot de
at the time the application is being used. Some other problems could be caused by the computer on which the application is being http://www.functionx.com/visualbasic/exceptions/errorhandling.htm used. While developing your application, you should anticipate as many problems as http://www.vbtutor.net/vb2008/vb2008_lesson20.html possible as take appropriate actions. Error Categories There are three main types of errors that could occur while your application is being used: Syntax Errors: A syntax error comes from your mistyping a word or forming a bad expression in your code. It could be that you misspelled a error handling keyword such as ByVel instead of ByVal. It could also be a bad expression. Examples are: 524+ + 62.55 if Number == 2 Number = 6 If you use the Microsoft Visual Basic IDE to write your code, it would point out the errors while you are writing your code, giving up time to fix them. There are other syntax errors that the error handling techniques IDE may not detect. This could come from using a data type or class that doesn't exist. When you compile your application, the compiler can let you know about other syntax errors. Those types of errors are those the compiler cannot execute. It this case, the compiler intercepts, stops, and lets you know. For this reason, syntax errors are almost the easiest to fix. Most of the time, the compiler would point out where the problem is so you can fix it. Run-Time Errors: After all syntax errors have been fixed, the program may be ready for the user. The time period a person is using an application is called run-time. There are different types of problems that a user may face when interacting with your program. For example, imagine that, in your code, you indicate that a picture would be loaded and displayed to the user but you forget to ship the picture or the directory of the picture indicated in your code becomes different when a user opens your application. In this case, when you compiled and executed the application in your machine, everything
error-free program can run smoothly and efficiently, otherwise all sorts of problems occur such as program crash or system hang. Errors often occur due to incorrect input from the user. For example, the user might make the mistake of attempting to enter a text (string) to a box that is designed to handle only numeric values such as the weight of a person, the computer will not be able to perform arithmetic calculation for text therefore will create an error. These errors are known as synchronous errors. Therefore a good programmer should be more alert to the parts of program that could trigger errors and should write errors handling code to help the user in managing the errors. Writing errors handling code should be considered a good practice for Visual Basic programmers, so do try to finish a program fast by omitting the errors handling code. However, there should not be too many errors handling code in the program as it create problems for the programmer to maintain and troubleshoot the program later. Visual Basic 2008 has improved a lot in built-in errors handling compared to Visual Basic 6. For example, when the user attempts to divide a number by zero, Vb2008 will not return an error message but gives the 'infinity' as the answer (although this is mathematically incorrect, because it should be undefined) 20.2 Using On Error GoTo Syantax Visual Basic 2008 still supports the VB6 errors handling syntax, that is the On Error GoTo program_label structure. Although it has a more advanced error handling method, we shall deal with that later.We shall now learn how to write errors handling code in VB2008. The syntax for errors handling is On Error GoTo program_label where program_label is the section of code that is designed by the programmer to handle the error committed by the user. Once an error is detected, the program will jump to the program_label section for error handling.
Example 20.1: Division by Zero In this example, we will deal with the error of entering non-numeric data into the textboxes that suppose to hold numeric values. The program_label here is error_hanldler. when the user