我有一个数据上下文(
UserPreferences)分配给我的主窗口，以及一个文本框，双向绑定到数据上下文的一个属性(CollectionDevice)中的属性之一。当窗口加载时，文本框不会绑定到我的模型中的属性。我在调试器中验证了数据上下文设置为模型对象，而且模型的属性正确地分配了。但是，我只得到一系列带有0的文本框。当我输入数据到文本框中时，数据会更新到模型中。问题仅发生在我加载数据并将其应用于数据上下文时，文本框不会更新。当我将模型保存到数据库时，来自文本框的正确数据会被保存。当我从数据库恢复模型时，正确的数据会被应用。当模型在我的构造函数中应用于数据上下文时，文本框的数据上下文包含正确的数据，并且它们的属性被分配为应该分配的值。问题是UI没有反映出来。 XAML
<Window.DataContext>
<models:UserPreferences />
</Window.DataContext>
<!-- Wrap pannel used to store the manual settings for a collection device. -->
<StackPanel Name="OtherCollectionDevicePanel">
<StackPanel Orientation="Horizontal">
<TextBlock VerticalAlignment="Center" Margin="10, 10, 0, 0" Text="Baud Rate" />
<TextBox Name="BaudRateTextBox" Text="{Binding Path=SelectedCollectionDevice.BaudRate, Mode=TwoWay}" Margin="10, 10, 0, 0" MinWidth="80" ></TextBox>
</StackPanel>
<WrapPanel>
<TextBlock VerticalAlignment="Center" Margin="10, 10, 0, 0" Text="Com Port" />
<TextBox Text="{Binding Path=SelectedCollectionDevice.ComPort, Mode=TwoWay}" Margin="10, 10, 0, 0" MinWidth="80" ></TextBox>
</WrapPanel>
<WrapPanel>
<TextBlock VerticalAlignment="Center" Margin="10, 10, 0, 0" Text="Data Points" />
<TextBox Text="{Binding Path=SelectedCollectionDevice.DataPoints, Mode=TwoWay}" Margin="10, 10, 0, 0" MinWidth="80" ></TextBox>
</WrapPanel>
<WrapPanel Orientation="Horizontal">
<TextBlock VerticalAlignment="Center" Margin="10, 10, 0, 0" Text="WAAS" />
<CheckBox IsChecked="{Binding Path=SelectedCollectionDevice.WAAS, Mode=TwoWay}" Content="Enabled" Margin="20, 0, 0, 0" VerticalAlignment="Bottom"></CheckBox>
</WrapPanel>
</StackPanel>
模型 <-- 数据上下文。
/// <summary>
/// Provides a series of user preferences.
/// </summary>
[Serializable]
public class UserPreferences : INotifyPropertyChanged
{
private CollectionDevice selectedCollectionDevice;
public UserPreferences()
{
this.AvailableCollectionDevices = new List<CollectionDevice>();
var yuma1 = new CollectionDevice
{
BaudRate = 4800,
ComPort = 31,
DataPoints = 1,
Name = "Trimble Yuma 1",
WAAS = true
};
var yuma2 = new CollectionDevice
{
BaudRate = 4800,
ComPort = 3,
DataPoints = 1,
Name = "Trimble Yuma 2",
WAAS = true
};
var toughbook = new CollectionDevice
{
BaudRate = 4800,
ComPort = 3,
DataPoints = 1,
Name = "Panasonic Toughbook",
WAAS = true
};
var other = new CollectionDevice
{
BaudRate = 0,
ComPort = 0,
DataPoints = 0,
Name = "Other",
WAAS = false
};
this.AvailableCollectionDevices.Add(yuma1);
this.AvailableCollectionDevices.Add(yuma2);
this.AvailableCollectionDevices.Add(toughbook);
this.AvailableCollectionDevices.Add(other);
this.SelectedCollectionDevice = this.AvailableCollectionDevices.First();
}
/// <summary>
/// Gets or sets the GPS collection device.
/// </summary>
public CollectionDevice SelectedCollectionDevice
{
get
{
return selectedCollectionDevice;
}
set
{
selectedCollectionDevice = value;
this.OnPropertyChanged("SelectedCollectionDevice");
}
}
/// <summary>
/// Gets or sets a collection of devices that can be used for collecting GPS data.
/// </summary>
[Ignore]
[XmlIgnore]
public List<CollectionDevice> AvailableCollectionDevices { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Notifies objects registered to receive this event that a property value has changed.
/// </summary>
/// <param name="propertyName">The name of the property that was changed.</param>
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
CollectionDevice <-- 文本框绑定到的位置。
/// <summary>
/// CollectionDevice model
/// </summary>
[Serializable]
public class CollectionDevice : INotifyPropertyChanged
{
/// <summary>
/// Gets or sets the COM port.
/// </summary>
private int comPort;
/// <summary>
/// Gets or sets a value indicating whether [waas].
/// </summary>
private bool waas;
/// <summary>
/// Gets or sets the data points.
/// </summary>
private int dataPoints;
/// <summary>
/// Gets or sets the baud rate.
/// </summary>
private int baudRate;
/// <summary>
/// Gets or sets the name.
/// </summary>
public string Name { get; set; }
/// <summary>
/// Gets or sets the COM port.
/// </summary>
public int ComPort
{
get
{
return this.comPort;
}
set
{
this.comPort= value;
this.OnPropertyChanged("ComPort");
}
}
/// <summary>
/// Gets or sets the COM port.
/// </summary>
public bool WAAS
{
get
{
return this.waas;
}
set
{
this.waas = value;
this.OnPropertyChanged("WAAS");
}
}
/// <summary>
/// Gets or sets the COM port.
/// </summary>
public int DataPoints
{
get
{
return this.dataPoints;
}
set
{
this.dataPoints = value;
this.OnPropertyChanged("DataPoints");
}
}
/// <summary>
/// Gets or sets the COM port.
/// </summary>
public int BaudRate
{
get
{
return this.baudRate;
}
set
{
this.baudRate = value;
this.OnPropertyChanged("BaudRate");
}
}
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Notifies objects registered to receive this event that a property value has changed.
/// </summary>
/// <param name="propertyName">The name of the property that was changed.</param>
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public override string ToString()
{
return this.Name;
}
}
有人可以指引我正确的方向吗？我猜问题出在我的XAML绑定上，但我找不到它。我需要它是双向绑定的，因为数据可以在应用程序生命周期内的任何时间更改（通过同步更新数据库），并且UI需要反映这些更改，但用户也可以通过UI对模型进行更改。
更新1
我尝试强制更新文本框数据绑定，但也没有起作用。
BindingExpression be = this.BaudRateTextBox.GetBindingExpression(TextBox.TextProperty);
be.UpdateSource();
我还尝试将UpdateSourceTrigger设置为PropertyChanged，但似乎也不能解决问题。
<TextBox Name="BaudRateTextBox" Text="{Binding Path=SelectedCollectionDevice.BaudRate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="10, 10, 0, 0" MinWidth="80" ></TextBox>
更新2
我尝试遵循一些来自 Microsoft 的文档，但似乎没有解决问题。窗口加载时数值仍然保持为0。在从数据库还原对象的状态后，绑定未被更新。虽然绑定已经连接好了，因为当我输入数据时，数据上下文得到了更新。由于某种原因，它表现得像单向绑定，尽管我把它设置成了双向绑定。
更新3
我尝试将代码移到窗口加载事件中并脱离构造函数，但这似乎没有帮助。我发现有趣的是，属性更改事件在反序列化过程中没有触发。在这种情况下，我不认为这有什么关系，因为对象已经完全恢复并且我只是将其分配给了数据上下文。我将数据上下文移出 XAML 并放入 WindowLoaded 中以测试 XAML 是否有问题，结果相同。
private void WindowLoaded(object sender, RoutedEventArgs e)
{
// Restore our preferences state.
var preferences = new UserPreferenceCommands();
Models.UserPreferences viewModel = new Models.UserPreferences();
// Set up the event handler before we deserialize.
viewModel.PropertyChanged += viewModel_PropertyChanged;
preferences.LoadPreferencesCommand.Execute(viewModel);
// At this point, viewModel is a valid object. All properties are set correctly.
viewModel = preferences.Results;
// After this step, the UI still shows 0's in all of the text boxs. Even though the values are not zero.
this.DataContext = viewModel;
}
// NEVER gets fired from within the WindowLoaded event.
void viewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
MessageBox.Show("Property changed!");
}
// This changes the model properties and is immediately reflected in the UI. Why does this not happen within the WindowLoaded event?
private void TestButtonClickEvent(object sender, RoutedEventArgs e)
{
var context = this.DataContext as Models.UserPreferences;
context.SelectedCollectionDevice.ComPort = 1536;
}
更新4 - 问题已经找到
我已经找到了问题，但是仍需要解决。数据绑定的整个意义在于我不必执行这个手动赋值。我的 INotify 实现是否有问题？
private void WindowLoaded(object sender, RoutedEventArgs e)
{
// Restore our preferences state.
var preferences = new UserPreferenceCommands();
Models.UserPreferences viewModel = new Models.UserPreferences();
// Set up the event handler before we deserialize.
viewModel.PropertyChanged += viewModel_PropertyChanged;
preferences.LoadPreferencesCommand.Execute(viewModel);
// At this point, viewModel is a valid object. All properties are set correctly.
viewModel = preferences.Results;
// After this step, the UI still shows 0's in all of the text boxs. Even though the values are not zero.
this.DataContext = viewModel;
// SOLUTION: - Setting the actual property causes the UI to be reflected when the window is initialized; setting the actual data context does not. Why? Also note that I set this property and my PropertyChanged event handler still does not fire.
((Models.UserPreferences) DataContext).SelectedCollectionDevice = viewModel.SelectedCollectionDevice;
}
List<CollectionDevice>更改为ObservableCollection<CollectionDevice>。 - EkoostikMartin