UpdateSourceTrigger不工作？

Question

我想在按下某個鍵時驗證文本框中的文本。這裏是最短的代碼示例顯示了我想要做的事：

<Window x:Class="WpfApplication1.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="MainWindow" Height="350" Width="525"> 
    <Grid> 
     <TextBox FontSize="15" HorizontalAlignment="Left" Name="txtEmail" VerticalAlignment="Top" Width="135" 
       Text="{Binding ValidationRules.EmailAddress, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}"/> 
    </Grid> 
</Window> 

「ValidationRules」類：

當我開始在文本框中鍵入，我不明白「設置」作爲控制檯輸出，儘管我使用的是UpdateSourceTrigger=PropertyChanged。我已經完成了我的研究，但我能找到的所有例子都是漫長而混亂的。如果你能指出我在驗證過程中遇到的其他錯誤，我也會很感激，但如果可能，請嘗試用簡單的術語來解釋，因爲我是WPF的新手。

Answer 1

它必須是您設置DataContext的位置的問題。

這個例子似乎很好地工作：

代碼：

public partial class MainWindow : Window, INotifyPropertyChanged 
{ 
    public MainWindow() 
    { 
     InitializeComponent(); 
     ValidationRules = new ValidationRules(); 
    } 

    private ValidationRules _validation; 
    public ValidationRules ValidationRules 
    { 
     get { return _validation; } 
     set { _validation = value; NotifyPropertyChanged("ValidationRules"); } 
    } 


    public event PropertyChangedEventHandler PropertyChanged; 
    private void NotifyPropertyChanged(string property) 
    { 
     if (PropertyChanged != null) 
     { 
      PropertyChanged(this, new PropertyChangedEventArgs(property)); 
     } 
    } 
} 

public class ValidationRules : INotifyPropertyChanged 
{ 
    string email = ""; 
    public string EmailAddress 
    { 
     get 
     { 
      return email; 
     } 

     set 
     { 
      Console.WriteLine("Setting!"); 
      //Only check if there is any text for now... 
      if (String.IsNullOrWhiteSpace(value)) 
      { 
       throw new Exception(); 
      } 
      email = value; 
      NotifyPropertyChanged("EmailAddress"); 
     } 
    } 

    public event PropertyChangedEventHandler PropertyChanged; 
    private void NotifyPropertyChanged(string property) 
    { 
     if (PropertyChanged != null) 
     { 
      PropertyChanged(this, new PropertyChangedEventArgs(property)); 
     } 
    } 

} 

的XAML

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     x:Class="WpfApplication1.MainWindow" 
     Title="MainWindow" Height="125.078" Width="236.441" x:Name="UI" > 
    <Grid DataContext="{Binding ElementName=UI}"> 
     <TextBox FontSize="15" HorizontalAlignment="Left" Name="txtEmail" VerticalAlignment="Top" Width="135" 
       Text="{Binding ValidationRules.EmailAddress, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}"/> 
    </Grid> 
</Window>