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.
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.
On the result of validation can depend many things.
For example I would like to bind button Is Enabled property to that deciding to enable button only in user input is valid.
What we want to do is a simple entry form for an e-mail address. Markup; --------------------- Hidden note: You have a mistype in the last parameter of this line: --------------------- public override Validation Result Validate(object value, Culture Info ulture Info) --------------------- It's "culture Info" with " C" instead of "ulture Info".
If the user enters an invalid e-mail address, the border of the textbox gets red and the tooltip is showing the reason. Problem: I tried to define <sys: String x: Key="email Regex"> but got the error that the TYPE "sys: String" NOT FOUND.
This slows down your application and causes the following message in your debug window: System. Data Error: 16 : Cannot get ‘Item‘ value (type ‘Validation Error’) from ‘(Validation. when you're new to WPF it's not obvious sometimes what goes where or what references are needed etc. How will you stop user from going to next page till user clears all validations on this page? As soon as user will click submit button, all client side validators will validate and of any of them fails then user remains on the same page. I have a little problem in this validation process.
Errors)’ (type ‘Read Only Observable Collection`1′). I don't wan't to show user the validation errors (red border on controls) before they try to save the form.
This expression works if there is one validation error.