WPF开发工具在实际使用中有很多功能的实现,需要我们去深入的探讨。比如这篇文章为大家介绍有关WPF密码的一些应用方法等。#t#
正如绑定TextBox控件的Text属性一样, 我们希望能够将PasswordBox空间的WPF密码Password属性进行绑定, 比如在MVVM模式中,这似乎是必须的, 但可惜的是, Password属性是不支持绑定的(不是依赖属性, 也没有实现INotifyPropertyChanged).
这可能是出于安全性的考虑. 但在我们的系统为了实现View层密码框中的密码与后台其它层之间的密码属性之间的绑定, 可以采取如下思路: 将密码框的密码和某一个缓冲区进行同步, 缓冲区在和后台进行绑定. 其中密码框与缓冲区之间的同步可采用事件进行通知, 并将缓冲区打造成依赖属性, 然后缓冲区就支持绑定了, 并给后台提供正确的密码.
缓冲区可以是哈希表或其他字典结构, 以便将WPF密码框和缓冲区中的密码一 一对应起来, 也可以使AttachProperty(附加属性), 其实附加属性的机制也就是对缓存了的一个大字典进行操作
- public static class Password
BoxBindingHelper- {
- public static bool GetIsPassword
BindingEnabled(DependencyObject obj)- {
- return (bool)obj.GetValue
(IsPasswordBindingEnabledProperty);- }
- public static void SetIsPassword
BindingEnabled(DependencyObject
obj, bool value)- {
- obj.SetValue(IsPasswordBinding
EnabledProperty, value);- }
- public static readonly Dependency
Property IsPasswordBinding
EnabledProperty =- DependencyProperty.Register
Attached("IsPasswordBinding
Enabled", typeof(bool),- typeof(PasswordBoxBindingHelper),
- new UIPropertyMetadata
(false, OnIsPasswordBinding
EnabledChanged));- private static void
OnIsPasswordBindingEnabled
Changed(DependencyObject obj,- DependencyPropertyChangedEventArgs e)
- {
- var passwordBox = obj as
PasswordBox;- if(passwordBox != null)
- {
- passwordBox.PasswordChanged
-= PasswordBoxPasswordChanged;- if ((bool)e.NewValue)
- {
- passwordBox.PasswordChanged
+= PasswordBoxPasswordChanged;- }
- }
- }
- //when the passwordBox's password
changed, update the buffer- static void PasswordBoxPassword
Changed(object sender, RoutedEventArgs e)- {
- var passwordBox = (PasswordBox) sender;
- if (!String.Equals(GetBindedPassword
(passwordBox),passwordBox.Password))- {
- SetBindedPassword(passwordBox,
passwordBox.Password);- }
- }
- public static string GetBindedPassword
(DependencyObject obj)- {
- return (string)obj.GetValue
(BindedPasswordProperty);- }
- public static void SetBindedPassword
(DependencyObject obj, string value)- {
- obj.SetValue(BindedPasswordProperty, value);
- }
- public static readonly Dependency
Property BindedPasswordProperty =- DependencyProperty.RegisterAttached
("BindedPassword", typeof(string),- typeof(PasswordBoxBindingHelper),
- new UIPropertyMetadata(string.Empty,
OnBindedPasswordChanged));- //when the buffer changed, upate
the passwordBox's password- private static void OnBindedPassword
Changed(DependencyObject obj,- DependencyPropertyChangedEventArgs e)
- {
- var passwordBox = obj as PasswordBox;
- if (passwordBox != null)
- {
- passwordBox.Password = e.NewValue ==
null ? string.Empty : e.NewValue.ToString();- }
- }
- }
在View层, 如下使用便可以了:
- < PasswordBox Helpers:PasswordBox
BindingHelper.IsPassword
BindingEnabled="True"- Helpers:PasswordBoxBinding
Helper.BindedPassword=- "{Binding Path=Password,
Mode=TwoWay, UpdateSource
Trigger=PropertyChanged}" />
另外, 在更改了密码框的WPF密码后, 需要手动更新密码框插入符(CaretIndex)的位置, 可惜的是, 密码框并没有给我们提供这样的属性或方法(TextBox有, PasswordBox没有), 可以采用下面的方法来设置:
- private static void SetPassword
BoxSelection(PasswordBox
passwordBox, int start, int length)- {
- var select = passwordBox.
GetType().GetMethod("Select",- BindingFlags.Instance |
BindingFlags.NonPublic);- select.Invoke(passwordBox,
new object[] { start, length });- }