Textarea not validating
You can do this by implementing a custom validation rule and associate this with the object at any given step, any errors that were added to the Validation.Errors attached property of the bound element during that step in a previous validation procedure are removed. Errors collection is also cleared when a valid value transfer occurs.But i would recommend you to go with code behind approach.In your code, define your specifications in properties setters and throw exceptions when ever it doesn't compliance to your specifications.Text shows the single character the user just entered.
Provided that the view model has a property called “Name”, you bind it to a Text Box’s Text property in XAML the following way: Besides the path that specifies the name of the property to bind to, the binding must also have a source object.Error Template attached property of the control: Note that the Validation.Error Template will be displayed on the adorner layer.WPF ships with two built-in concrete implementations of the object to the Validation.
Errors collection when an exception is thrown in the setter of the source property.If you don’t specify a source explicitly by setting the Source property of the binding, it will inherit the Data Context from its parent element to use as its source.