UWP：在设置另一个属性后设置属性的例外情况

我想我的UWP应用程序中有一个线程问题。 我想做一个非常简单的事情：

• 带有2个数字字段的UI;
• 如果在field1键入数字值，我希望field2被设置为field1的比例（例如： field2 = ratio * field1 ）。

我正在使用x:Bind和TextChanging事件。 由于未知的原因，我无法在XAML中“调用” TextChanging事件，而不会在启动时发生exception。 因此，我正在使用Loaded事件。

这是我的模型类，简称为MyModel ：

 public class MyModel : INotifyPropertyChanged { private readonly uint r1 = 3; private uint _field1; public uint Field1 { get { return this._field1; } set { this.Set(ref this._field1, value); if (value == 0) { Field2 = 0; } else { Field2 = value * r1; } } } private uint _field2; public uint Field2 { get { return this._field2; } set { this.Set(ref this._field2, value); } } public event PropertyChangedEventHandler PropertyChanged; protected void RaisedPropertyChanged([CallerMemberName]string propertyName = null) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); } protected bool Set<T>(ref T storage, T value, [CallerMemberName]string propertyName = null) { if (Equals(storage, value)) { return false; } else { storage = value; this.RaisedPropertyChanged(propertyName); return true; } } } 

我的ViewModel：

• 让键盘越过UI不会改变UWP中的整个UI
• testingUWP蓝牙应用程序
• 如何从资源加载样式
• UWP应用程序分配访问和Windows Store for Business – 当应用程序更新可用时会发生什么情况？
• 如何知道相机目前正在被另一个UWP应用程序使用？

 public class MyModelViewModel : INotifyPropertyChanged { public MyModel MyModel { get; set; } public MyModelViewModel() { // Initialisation de notre page this.MyModel = new MyModel() { Field1 = 0 }; } public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); } } 

我的代码背后（我正在筛选input，以避免转换exception）：

 public sealed partial class MainPage : Page { public MyModelViewModel ViewModel { get; set; } = new MyModelViewModel(); public MainPage() { this.InitializeComponent(); } private void InitField1(object sender, Windows.UI.Xaml.RoutedEventArgs e) { field1.TextChanging += field1_TextChanging; } private void InitField2(object sender, Windows.UI.Xaml.RoutedEventArgs e) { field2.TextChanging += field2_TextChanging; } private void field1_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args) { var error = errorTextBlock; error.Visibility = Windows.UI.Xaml.Visibility.Collapsed; Regex regex = new Regex("[^0-9]+"); // All but numeric if (regex.IsMatch(sender.Text)) { error.Text = "Non numeric char"; error.Visibility = Windows.UI.Xaml.Visibility.Visible; sender.Text = this.ViewModel.MyModel.Field1.ToString(); } else { this.ViewModel.MyModel.Field1 = Convert.ToUInt32(sender.Text); } } private void field2_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args) { var error = errorTextBlock; error.Visibility = Windows.UI.Xaml.Visibility.Collapsed; Regex regex = new Regex("[^0-9]+"); if (regex.IsMatch(sender.Text)) { error.Text = "Non numeric char"; error.Visibility = Windows.UI.Xaml.Visibility.Visible; sender.Text = this.ViewModel.MyModel.Field2.ToString(); } else { this.ViewModel.MyModel.Field2 = Convert.ToUInt32(sender.Text); } } } 

最后，我的XAML：

 <TextBlock Grid.Row="0" Grid.Column="0" x:Name="errorTextBlock" Text="" Visibility="Collapsed" /> <TextBlock Grid.Row="1" Grid.Column="0" Text="Field 1" /> <TextBox Grid.Row="1" Grid.Column="1" x:Name="field1" Text="{x:Bind ViewModel.MyModel.Field1, Mode=OneWay}" Loaded="InitField1" /> <TextBlock Grid.Row="2" Grid.Column="0" Text="Field 2" /> <TextBox Grid.Row="2" Grid.Column="1" x:Name="field2" Text="{x:Bind ViewModel.MyModel.Field2, Mode=OneWay}" Loaded="InitField2" /> 

在运行时，如果我在字段1中键入一个非数字字符，input被过滤，字段1返回到它的以前的值没有屏幕“闪烁”（这就是为什么我使用TextChanging事件，而不是TextChanged ）。 完善！ 但是，如果我键入一个数字字符， field1正确更新（我可以看到与断点），但是当field2设置时，我调用RaisedPropertyChanged时得到本机exception：

我怀疑某种线程错误，但是我对这种开发很新颖。 任何想法？ 谢谢！

 <StackPanel> <TextBlock Text="Value 1" /> <TextBox Text="{x:Bind ViewModel.MyModel.Value1, Mode=TwoWay}" /> <TextBlock Text="Value 2" /> <TextBox Text="{x:Bind ViewModel.MyModel.Value2, Mode=OneWay}" IsReadOnly="True" /> </StackPanel> 

 public MyViewModel ViewModel { get; set; } = new MyViewModel(); 

 public class MyViewModel { public MyModel MyModel { get; set; } = new MyModel(); } 

 public class MyModel : INotifyPropertyChanged { private string _value1; public string Value1 { get { return _value1; } set { if (_value1 != value) { _value1 = value; // Cause the updated value to be displayed on the UI OnPropertyChanged(nameof(Value1)); // Is the entered value a number (int)? int numericValue; if (int.TryParse(value, out numericValue)) { // It's a number so set the other value // multiplied by the ratio Value2 = (numericValue * 3).ToString(); } else { // A number wasn't entered so indicate this Value2 = "NaN"; } // Cause the updated value2 to be displayed OnPropertyChanged(nameof(Value2)); } } } // We can use the automatic property here as don't need any logic // relating the getting or setting this property public string Value2 { get; set; } public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); } } 

  <TextBox Text="{Binding ViewModel.Value1, Mode=TwoWay}" TextChanged="TextBox_OnTextChanged" /> 

 private void TextBox_OnTextChanged(object sender, TextChangedEventArgs e) { var be = (sender as TextBox).GetBindingExpression(TextBox.TextProperty); be.UpdateSource(); } 

 public MainPage() { this.InitializeComponent(); this.DataContext = this; }