![]() I'm sure most people will agree that throwing exceptions isn't really the optimal way of signaling that we have user input errors. If you remember our customer's Name property above, you'll remember we were throwing an exception in order to display the errors using an ExceptionValidationRule. I know what you're thinking: "Do I have to throw exceptions?" To achieve the look you're after, you could define your own control template: You might want thick green borders with orange exclamation marks: If the default red borders aren't your thing, I'll understand. ErrorTemplate - A ControlTemplate we can apply if there is an error.īy default, the Validation class uses an ErrorTemplate that has a red border around the control, which is why we get a red border in the program above.HasError - Indicates whether there are any errors in the Errors property.Errors - A list of error messages that apply to the bindings on this control.It has a number of static dependency properties which you can apply to any control. Windows Presentation Foundation has a static class inside the namespace, imaginatively named " Validation". If you ran this code, you'd see something which looks like this: However, even if you're convinced that validating on the UI is a Bad Idea (TM), I'd encourage you to read the full article as I'll discuss some of the other validation features in WPF that you can still leverage. Luckily, since I too was disappointed about having to enforce everything "on the UI", towards the end of the article, I'll show how to create an ErrorProvider for use in your Windows Presentation Foundation applications. On the other hand, if you did spend a lot of time using Windows Forms, and made heavy use of the ErrorProvider/ IDataErrorInfo approach to validation, you might be disheartened to know that there isn't one in Windows Presentation Foundation. As we approach the end of the article, I'll discuss why this is and a way to do things differently, but still leveraging some of the strengths of WPF. This approach is quite simple to understand and implement, but some proponents of "rich domain models" and object-oriented designs (including myself) have some problems with it. ![]() Validation in Windows Presentation Foundation takes an approach very similar to ASP.NET validation, in that most "business rules" are enforced on the user interface and applied to specific controls and bindings. ![]() If you never spent much time with Windows Forms or data binding, I'm hoping that this article will remain simple enough to follow along. Controlling When to Validate: UpdateSourceTriggers.Very Simple Validation: ExceptionValidationRule.Specifically, I'll discuss the ExceptionValidationRule class, creating custom ValidationRules, how to display errors, when to display errors ( UpdateSourceTriggers), and finally, an alternative approach using an implementation of the Windows Forms ErrorProvider for WPF. In this article, I'll discuss how input validation is designed to be handled in Windows Presentation Foundation (hereafter referred to as WPF). In Windows Presentation Foundation, the approach is going to change, but the goal remains the same: telling users that something is wrong. Under Windows Forms, we had the ErrorProvider, and under ASP.NET, we had Validator controls. NET 4.0, most of us generally have to resort to displaying some kind of UI cues to politely tell the user what they've done wrong, and how they can fix it. After decades of the existence of computers, why do we still need to inform users that "the Start Date should always be less than the End Date", or that "First Name is a required field"? Since () won't be added to the. ![]() Since the dawn of software development, the single biggest threat to reliable information has been end-users.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |