我创建了一个简单的测试项目，该项目创建了填充有复选框的ListBox。我有一些代码提示，每当选中复选框时，ListBox上方的TextBox都会显示所有选定项的文本。一切都正常，但我现在正试图创建一个允许包含前缀的附加属性(再次在后面的代码中(。最终，我希望将其转换为MVVM标准，但由于我对WPF相对较新，对MVVM也非常陌生，我喜欢从一个工作示例项目开始工作，并逐渐将每个部分转换为一个MVVM项目，因为我发现这有助于我更好地了解正在发生的事情。我的代码如下：
xaml:
<Window x:Class="CheckBoxList.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:CheckBoxList"
mc:Ignorable="d"
Title="MainWindow" Height="400" Width="400">
<Window.Resources>
<Style x:Key="CheckBoxListStyle" TargetType="{x:Type ListBox}">
<Setter Property="SelectionMode" Value="Multiple"></Setter>
<Setter Property="ItemContainerStyle">
<Setter.Value>
<Style TargetType="{x:Type ListBoxItem}" >
<Setter Property="Margin" Value="2" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<CheckBox
IsChecked="{Binding Path=IsSelected,RelativeSource={RelativeSource TemplatedParent},Mode=TwoWay}"
Checked="CheckBox_Checked" Unchecked="CheckBox_Unchecked">
<ContentPresenter></ContentPresenter>
</CheckBox>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<Grid Margin="8">
<Grid.RowDefinitions>
<RowDefinition Height="30"/>
<RowDefinition/>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="30"/>
</Grid.RowDefinitions>
<TextBox Grid.Row="0" x:Name="ListBoxTextBox"/>
<ListBox Grid.Row="1" Style="{StaticResource CheckBoxListStyle}" Name="lstProducts" local:MainWindow.PrefixMark=">"
DisplayMemberPath="ModelName">
</ListBox>
<Button Grid.Row="2" Margin="0,5,0,0" Click="cmdGetSelectedItems">Get Selected Items</Button>
<CheckBox Grid.Row="3" Content="Test" Margin="5"/>
</Grid>
xaml.cs
public static string GetPrefixMark(DependencyObject obj)
{
string t = (string)obj.GetValue(PrefixMarkProperty);
return (string)obj.GetValue(PrefixMarkProperty);
}
public static void SetPrefixMark(DependencyObject obj, string value)
{
obj.SetValue(PrefixMarkProperty, value);
string t = (string)obj.GetValue(PrefixMarkProperty);
}
// Using a DependencyProperty as the backing store for PrefixMark. This enables animation, styling, binding, etc...
public static readonly DependencyProperty PrefixMarkProperty =
DependencyProperty.RegisterAttached("SetPrefixMark", typeof(string), typeof(MainWindow), new PropertyMetadata("('"));
private void CheckBox_Checked(object sender, RoutedEventArgs e)
{
if (sender is FrameworkElement element)
{
AddText(element);
}
}
private void AddText(FrameworkElement e)
{
StringBuilder sB = new StringBuilder("");
foreach (Product product in lstProducts.SelectedItems)
{
sB.Append(product.ModelName).Append(ValueSeparator);
}
if (sB.Length > 0)
{
sB.Remove(sB.Length - (ValueSeparator).Length, (ValueSeparator).Length);
}
if (sB.Length > 0)
{
ListBoxTextBox.Text = GetPrefixMark(e) + sB.ToString();
}
else
{
ListBoxTextBox.Text = "";
}
}
当我运行程序时，尽管PrefixMark设置为Load，但当我选中复选框时，它会恢复到默认值。我只能假设这是两次创建的，但就我而言，我不知道为什么以及如何解决这个问题？
您应该将依赖属性的实际名称传递给Register方法，以开始：
DependencyProperty.RegisterAttached("PrefixMark", ...
SetPrefixMark在启动时不再被激发
这是不应该的。如果你想在启动时设置TextBox的Text属性，你应该将其绑定到源属性或以编程方式设置：
public MainWindow()
{
InitializeComponent();
ListBoxTextBox.Text = GetPrefixMark(this);
...
}