C# 当绑定到itemsource WPF C时，组合框显示-1元素#

我有这样一份清单：

List<string> test = new List<string>() { "1","2","3" };

当我启动程序时，组合框选择了-1元素（空）。现在，当我单击它时，它将显示列表中的3个项目。但是，当我选择其中一个项目时，我不能再次将其设置为空。有没有办法让我在不编辑列表的情况下再次选择空字段

Xaml：

---

只需在要进行空选择的地方键入以下代码即可

comboBox1.SelectedIndex = -1;

---

如果未在combo ItemsSource集合中定义此值，则无法拾取空值。但是，您可以将组合设置为可编辑，然后只删除选定的值。代码如下： 1.Xaml代码：

Window x:Class="ComboBoxSoHelpAttempt.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:collections="clr-namespace:System.Collections;assembly=mscorlib"
    xmlns:system="clr-namespace:System;assembly=mscorlib"
    xmlns:comboBoxSoHelpAttempt="clr-namespace:ComboBoxSoHelpAttempt"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <comboBoxSoHelpAttempt:Null2StringConverter x:Key="Null2StringConverter" />
</Window.Resources>
<Window.DataContext>
    <comboBoxSoHelpAttempt:ComboViewModel/>
</Window.DataContext>
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
    <ComboBox ItemsSource="{Binding ComboItems}" HorizontalAlignment="Center" VerticalAlignment="Center" 
              IsEditable="True" SelectedValue="{Binding ComboSelectedValue}" 
              DisplayMemberPath="Name" SelectedValuePath="Id" Width="150"/>
    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Bottom" Foreground="Tomato"
        Text="{Binding ComboSelectedValue, Mode=Default, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource Null2StringConverter}}"/>
</StackPanel></Window>

四,。转换器代码：

public class Null2StringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value == null ? "Null" : value.ToString();
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

五,。BaseObserveObject是INotifyPropertyChanged接口的简单实现

它看起来怎么样

如果我的代码出现问题，我很乐意提供帮助。

---

关于，

您的代码中的以下内容有什么

combobox1.DisplayMemberPath=；combobox1.WPF中SelectedValuePath的绑定与WinForms和WebForms中的绑定不同。。选中此链接，然后设置组合框1。SelectedIndex=0

FYI

SelectedIndex保证是唯一的，SelectedItem不理解您所说的内容，但我无法编辑列表。我希望名单保持不变。绑定到列表并没有什么问题，它确实显示了列表中的每个对象，只是当我选择了一个项目时，我希望能够取消选择一个项目。我可以制作一个按钮，将组合框设置为selecteditem=-1，但我不想这样做。也许你需要阅读一下如何在WPF中正确使用
绑定
这在WinForms和WebForms中效果很好。你的Xaml是什么样子的..请更新/编辑你的问题并将其粘贴到评论中，这对我们没有好处吗
Window x:Class="ComboBoxSoHelpAttempt.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:collections="clr-namespace:System.Collections;assembly=mscorlib"
    xmlns:system="clr-namespace:System;assembly=mscorlib"
    xmlns:comboBoxSoHelpAttempt="clr-namespace:ComboBoxSoHelpAttempt"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <comboBoxSoHelpAttempt:Null2StringConverter x:Key="Null2StringConverter" />
</Window.Resources>
<Window.DataContext>
    <comboBoxSoHelpAttempt:ComboViewModel/>
</Window.DataContext>
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
    <ComboBox ItemsSource="{Binding ComboItems}" HorizontalAlignment="Center" VerticalAlignment="Center" 
              IsEditable="True" SelectedValue="{Binding ComboSelectedValue}" 
              DisplayMemberPath="Name" SelectedValuePath="Id" Width="150"/>
    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Bottom" Foreground="Tomato"
        Text="{Binding ComboSelectedValue, Mode=Default, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource Null2StringConverter}}"/>
</StackPanel></Window>

 public class ComboViewModel:BaseObservableObject
{
    private string _comboSelectedValue;

    public ComboViewModel()
    {
        ComboItems = new ObservableCollection<ComboItem>
        {
            new ComboItem {Name = "Bob", Id = "1"},
            new ComboItem {Name = "Joe", Id = "2"},
            new ComboItem {Name = "John", Id = "3"},
            new ComboItem {Name = "Roi", Id = "4"},
        };
    }

    public ObservableCollection<ComboItem> ComboItems { get; set; }

    public string ComboSelectedValue
    {
        get { return _comboSelectedValue; }
        set
        {
            _comboSelectedValue = value;
            OnPropertyChanged();
        }
    }
}

 public class ComboItem:BaseObservableObject
{
    private string _name;
    private string _id;

    public string Name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }

    public string Id
    {
        get { return _id; }
        set
        {
            _id = value;
            OnPropertyChanged();
        }
    }
}

public class Null2StringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value == null ? "Null" : value.ToString();
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}