Also, the attribute can be added to form controls, to programmatically indicate that they are required.
Most current web browsers support this attribute and will communicate missing required input to the user, using standard web browser dialog mechanisms.
Client-side validation alone does not ensure security; therefore data needs to be validated on the server-side as well.
In a MVVM WPF application, the view model acts as the window’s Data Context: This means that that all controls inside the window will inherit its Data Context unless some parent element of a control overrides this by setting its own Data Context property.
Besides inheriting and setting the Data Context property on an element directly you can also specify a binding source using the Element Name property, used when you want to bind to some other element, or the Relative Source property.
A common requirement for any user interface application that accepts user input is to validate the entered information to ensure that it has the expected format and type for the back-end to be able to accept and persist it.
This post is about how data validation works in WPF and the different validation options there are available including implementing custom Validation Rules and using the In a typical WPF application that uses the MVVM (Model-View-View Model) design pattern, a dependency property of a user interface control in a XAML-defined view uses data binding to bind to some data returned by a CLR property of the view model.
In addition to providing instructions, validate user input to help users avoid mistakes.