![]() ![]() Setting this property to False allows the validation process to continue.Ī problem with this approach is that if the users enter an invalid value and tries to close the application, by default, they won't be able to do it. Setting this property to True is a signal back to the control that the validation failed in the code that handles the event and this results that the focus won't leave the control, forcing the user to enter a correct value. This event defines an event argument (CancelEventArgs) which contains the Boolean property named Cancel to set a signal that the event being fired should not be completed. The Validating event is the one that handles most of the validation logic. The Validated event is fired when the input is accepted as valid. The Validating event is intended to fire immediately after input has been completed but not accepted as valid. This prevents you to write a lot of validation code.Įvery control exposes two events: Validating and Validated. In complex controls like DataGridView control, we have built-in support for displaying validation errors as well. As well as the ErrorProvider component notifies the user of any validation problems. Data-bound controls raise events when validation occurs, giving the opportunity to write validation logic. In Windows Forms programming, validation is based around controls and events. Validations concerns about checking data entry and making sure it is valid based on the criteria of the application requirements. The example is based on a Windows Forms control developed by me which is based on the TextBox control and handles validation in a standardized way in order to detect input errors and display them to users. In this article, I will cover the principles and techniques built into Microsoft.NET for dealing with validation and error handling in the client-side. The refining of the data is done later, when the data is passed to another layer for processing. This eliminates the possibility the end-users will incorrectly enter the values. Therefore, this is the first place where the validation should be done. But the key components, which the end-users interact with, are those which reside in the presentation layer. Should this validation be done on the client-side or the server-side in a client/side application? Should this validation be done in the business layer or in the middleware component of a multi-layer application? Some checks are business rules and thus conceptually they must be done in the business layer of the multi-layer application or in the server-side of a client/server application. There is a deep discussion about when, where and how this validation should be done. Validation means that any data input meets the application requirements in order to ensure consistency and correctness of the data. An important part of any data-driven application is ensuring data validation and handling errors when they occur.
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