.NET Reference Guide

Displaying Errors with the Error Provider

Last updated Aug 19, 2004.

One of the more difficult parts of any user interface is error detection and notification. When the user fills out a form and submits it, the program must verify that the data is valid before saving it to a database or continuing with processing. If the program finds errors in the user's input data, then it must display some kind of error notification. Over the years, programmers have used many different error notification schemes with message boxes or form icons. Windows Forms formalizes and standardizes the error notification process with the ErrorProvider component.

A Simple Example

As an example of using the ErrorProvider, consider the "New Contact" dialog box for a simple telephone book application. A sample dialog is shown in Figure 1.

Figure 1

Data entry rules are very simple. The user must enter values for both fields, and the Phone field must contain a 10-digit number entered with no punctuation. For example, the number (702)555-1212 would be entered 7025551212. If all of these conditions are met, the program accepts the data input, signified by a message box. If any one or more of the conditions is not met, the program should indicate the error and allow the user to fix it. The program indicates the error by placing an exclamation icon next to the control that is in error. The user can hover the mouse over the icon to see the error message. An example is shown in Figure 2.

Figure 2