Wpf textbox error validating
This update behavior can be specified from the Update Source Trigger binding parameter.For instance, setting the Update Source Trigger parameter to Property Changed, updates the source property as the target property is updated.The binding makes use of the Two-Way binding mode to also passes input data at the target to the underlying data encapsulated by the source property.The Two-Way binding behavior is, by default, to update the source property when the bound control loses focus.To validate the editor when the user presses the Enter key, set the Validate On Enter Key Pressed property to True. Use the same approach to customize the Last Name, Email, Password, Birthday, Gender editor fields.It is not necessary to check if the Confirm Password editor field is non-empty, because the validation here implies checking if the Confirm Password box matches the string in the Password box.What remains is to customize the editors to handle this logic.You don't need to validate the editor while the user is typing, so set the editor Validate On Text Input property to False.
Set the editor's Validate On Text Input property to True.
My template shows a warning sign and a label explaining error made by user (why input is invalid): Read more about Adorned Element here.
On the result of validation can depend many things.
Only after validation succeeds, the editor posts the input value to its Edit Value property. The Validate On Enter Key Pressed property controls whether the Edit Value property is updated when the Enter key is pressed.
DXEditors provide two properties for invoking the validation mechanism: Base Edit. The Validate On Text Input property determines whether the Edit Value property is updated as the end-user types in the editor.
Sample problem: set parameter by entering value into a Text Box, check if value is a number in given range, allow clicking a Button if validation was successful. In this example a derived class Double Range Rule will check if user entered a number (double) within a given range (between Max and Min value).