我有一个分配给我的主窗口的数据上下文（UserPreferences），以及一个文本框，它在上下文中的一个数据上下文属性（CollectionDevice）内与属性双向绑定。
加载窗口时，文本框不会绑定到模型中的属性。我在调试器中验证数据上下文是否设置为模型对象，并且模型的属性已正确分配。然而，我得到的是一系列带有0的文本框。
当我将数据输入文本框时，数据会在模型中更新。当我加载数据并将其应用于数据上下文时，问题才会发生，文本框不会更新。
当我将模型保存到数据库时，会从文本框中保存正确的数据。当我从数据库恢复模型时，将应用正确的数据。当模型应用于构造函数中的数据上下文时，文本框的datacontext包含正确的数据，并且它的属性按原样分配。问题是用户界面没有反映这一点。
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＆lt; - Datacontext。
/// <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 ＆lt; - 文本框绑定的位置。
/// <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;
}
}
有人能指出我正确的方向吗？我认为这个问题是我在XAML中的约束力;我找不到它。我需要它是双向绑定的，因为数据可以在模型中的应用程序生命周期内随时更改（数据库通过同步更新）并且UI需要反映这些更改，但用户可以通过以下方式将更改应用于模型用户界面。
更新1
我试图强制更新文本框数据绑定，但这样做也不行。
BindingExpression be = this.BaudRateTextBox.GetBindingExpression(TextBox.TextProperty);
be.UpdateSource();
我也尝试将UpdateSourceTrigger设置为PropertyChanged，但似乎也无法解决问题。
<TextBox Name="BaudRateTextBox" Text="{Binding Path=SelectedCollectionDevice.BaudRate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="10, 10, 0, 0" MinWidth="80" ></TextBox>
更新2
我尝试跟随一些documentation from Microsoft并且它似乎没有解决问题。窗口加载时，值仍为0。从数据库恢复对象的状态后，绑定未更新。虽然绑定是连接的，但是当我输入数据时，数据上下文会更新。出于某种原因，当我将它设置为双向时，它就像单向一样。
更新3
我试图将代码移动到窗口加载的事件中并从构造函数中移出，但这似乎没有帮助。我发现有趣的是，在反序列化过程中不会触发PropertyChanged事件。在这种情况下，我认为它不重要，因为对象已完全恢复正常，然后我只是将它分配给数据上下文。我将数据上下文移出XAML并移入WindowLoaded，以测试XAML是否是问题。结果是一样的。
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 - 发现问题
我已经确定了问题，但仍需要一个解决方案。数据绑定的全部意义在于我不必执行此手动分配。我的INotify实现有问题吗？
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;
}
答案 0 :(得分：44)
默认情况下，TextBox的Text属性仅在对焦点丢失时才会更新。
您是否使用DataContext验证了它？
如果要覆盖此行为，则必须以这种方式包含属性UpdateSourceTrigger：
Text="{Binding Path=SelectedCollectionDevice.BaudRate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}
将UpdateSourceTrigger的值设置为PropertyChanged，当您更改绑定属性的值时，只要文本发生更改，更改就会反映在TextBox中。
有关UpdateSourceTrigger属性用法的有用教程是here。
答案 1 :(得分：5)
好吧，我能够确定问题并解决问题。事实证明这是导致这种情况的汇编。
首先，我的模特。
UserPreferences ＆lt; - MainWindow是绑定到此的数据。
[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;
if (selectedCollectionDevice.Name == "Other")
{
this.AvailableCollectionDevices[3] = 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));
}
}
}
在SelectedCollectionDevice的设置器中，我不想查看所选设备是否其他。所有其他设备（yuma1，panasonic等）都具有永不改变的预定属性值。当用户选择“其他”时，将显示文本框，并且他们可以手动输入数据。问题是当在窗口加载期间从数据库恢复手动输入的数据时，我没有将SelectedCollectionDevice中的自定义数据分配给集合中的相应对象。
在窗口加载期间，Combobox.SelectedItem设置为SelectedCollectionDevice的索引。 Combobox.ItemsSource已设置为AvailableCollectionDevices集合。
this.CollectionDevice.SelectedIndex =
viewModel.AvailableCollectionDevices.IndexOf(
viewModel.AvailableCollectionDevices.FirstOrDefault(
acd => acd.Name == viewModel.SelectedCollectionDevice.Name));
执行上述代码时，组合框会从其数据源中提取默认对象，该数据源的所有值都设置为零。在组合框的SelectionChanged事件中，我将数据上下文SelectedCollectionDevice分配给与组合框关联的零输出项。
private void CollectionDeviceSelected(object sender, SelectionChangedEventArgs e)
{
if (e.AddedItems.Count > 0 && e.AddedItems[0] is CollectionDevice)
{
// Assign the view models SelectedCollectionDevice to the device selected in the combo box.
var device = e.AddedItems[0] as CollectionDevice;
((Models.UserPreferences)this.DataContext).SelectedCollectionDevice = device;
// Check if Other is selected. If so, we have to present additional options.
if (device.Name == "Other")
{
OtherCollectionDevicePanel.Visibility = Visibility.Visible;
}
else if (OtherCollectionDevicePanel.Visibility == Visibility.Visible)
{
OtherCollectionDevicePanel.Visibility = Visibility.Collapsed;
}
}
}
很长一段时间，我在SelectedCollectionDevice的设置器中添加了上面的代码，以将值应用于AvailableCollectionDevices列表＆lt;＆gt;。这样，当组合框选择了“其他”值时，它会使用正确的数据从集合中提取值。在反序列化期间，我只是反序列化SelectedCollectionDevice而不是列表＆lt;＆gt;这就是为什么在首次加载窗口时数据总是被覆盖的原因。
这也解释了为什么使用本地SelectedCollectionDevice重新分配数据上下文viewModel.SelectedCollectionDevice属性的原因。我正在替换与组合框关联的零对象，该组合框在SelectionChanged事件期间设置了数据上下文。我无法在XAML中设置DataContext并删除手动分配。
感谢所有帮助，它帮助我缩小调试范围，直到我最终解决了问题。非常感谢！
答案 2 :(得分：3)
不是答案，但想发布适用于我的机器的代码以帮助OP ...
完整的xaml页面......
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Grid>
<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>
<Button Click="ButtonBase_OnClick" Content="Set ComPort to 11"></Button>
</StackPanel>
</Grid>
</Window>
完整的代码背后......
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Xml.Serialization;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
DataContext = new UserPreferences();
}
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
{
((UserPreferences) DataContext).SelectedCollectionDevice.ComPort = 11;
}
}
/// <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>
[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));
}
}
}
/// <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;
}
}
}
答案 3 :(得分：0)
我有同样的问题。我的问题是绑定属性名称错了。如果查看输出窗口，可以在运行时看到所有绑定错误。
System.Windows.Data错误：40：BindingExpression路径错误： ＆＃39; SelectedProtectedWebsiteTemplate＆＃39;在＆＃39; object＆＃39;上找不到的属性 ＆＃39;＆＃39; ProtectedWebsitesViewModel＆＃39; （的HashCode = 32764015）＆＃39 ;. BindingExpression：路径= SelectedProtectedWebsiteTemplate.Name; 的DataItem =＆＃39; ProtectedWebsitesViewModel＆＃39; （的HashCode = 32764015）;目标 元素是＆＃39; TextBox＆＃39; （名称=＆＃39;＆＃39）;目标属性是＆＃39; Text＆＃39; （类型 ＆＃39;字符串＆＃39）