mvvm - Input validation on Windows store app -

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I have a two-way binding in a window store app using MVVM in which only numeric values ​​should be allowed. What is the proper procedure to use MVVM when a non-numeric key is pressed?

INOTifyPropertyChanged value is being converted as text boxes Focus loses I basically want quick verification of your qualities I could not find a simple example of the

< / Div>

Why not create an affiliate property to include this behavior? Something like this: 

  public class TextBoxHelper {public static bool GetRestrictToNumerical (DependencyObject obj) {return (bool) obj.GetValue (RestrictToNumericalProperty); } Public static zero SetRestrictToNumerical (dependency object obj, bool value) {obj.SetValue (restricted ToNumericalProperty, value); } Public static DependencyProperty RestrictToNumericalProperty = DependencyProperty.RegisterAttached ( "RestrictToNumerical", typeof (bool), typeof (TextBoxHelper), New PropertyMetadata (wrong, onRestrictToNumericalChanged)) read-only; Private Statik Arkshittumumerik Chenjed (dependence on space object D, Dispennseeporfti Chenjed Aventarj e) as {var TB = D text box; If return (TB == blank); If ((bool e.NewValue) tb.KeyDown + = tb_KeyDown; Else tb.KeyDown - = tb_KeyDown; } Fixed zero tb_KeyDown (Object Sender, Windows.UI.Xaml.Input.KeyRoutedEventArgs e) {e.Handled = e.Key & lt; VirtualKey.Number0 || E. K & gt; VirtualKey.Number9; }}

You will use this in your XML: 

  & lt; Page x: Class = "App4.MainPage" xmlns = "http: //schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns: x = "http://schemas.microsoft.com/winfx/2006/ xaml "xmlns: local = using": App4 "xmlns: d =" Http://schemas.microsoft.com/expression/blend/2008 "xmlns: mc =" http://schemas.openxmlformats.org/markup -compatibility / 2006 "MC: Ignorable =" d "& gt; & Lt; Grid Background = "{ThemeResource ApplicationPageBackgroundThemeBrush}" & gt; & Lt; Text box vertical alignment = "center" local: textbox ornamentation. Rationality = "True" InputScope = "Number" /> & Lt; / Grid & gt; & Lt; / Page & gt; In my opinion, in my opinion, there is a clean MVVM approach for all input considerations that you may have to make. It is probably more likely for your simple question, but this is more sophisticated assumptions. Good for

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