Question

我正在尝试使用组合框来处理绑定，以便最终可以将其用于某些设置。我可以从一个可观察的集合中获取要填充的项目并绑定“SelectedItem”＃39;到财产SelectedItem="{x:Bind SelectedComboBoxOption}"

但是当我更改选择时，这并未反映在文本框中也绑定到此属性。在它背后的代码中，在启动时设置属性一次，但在更改组合框中的项时不设置。我必须遗漏一些东西，但我不清楚是什么。有什么想法吗？

这是XAML：

<Page
x:Class="ComboBoxTest.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:ComboBoxTest"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <StackPanel>
        <ComboBox 
            Name="ComboBox" 
            ItemsSource="{x:Bind ComboBoxOptions}" 
            SelectedItem="{x:Bind SelectedComboBoxOption, Mode=TwoWay}" 
            SelectedValuePath="ComboBoxOption" 
            DisplayMemberPath="ComboBoxHumanReadableOption"  
            Header="ComboBox" >
        </ComboBox>
        <TextBlock Name="BoundTextblock" Text="{x:Bind SelectedComboBoxOption}"/>
    </StackPanel>
</Grid>

这就是背后的代码：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;



namespace ComboBoxTest
{

 public sealed partial class MainPage : Page, INotifyPropertyChanged
 {

    private ObservableCollection<ComboBoxItem> ComboBoxOptions;

    public MainPage()
    {
        this.InitializeComponent();
        ComboBoxOptions = new ObservableCollection<ComboBoxItem>();
        ComboBoxOptionsManager.GetComboBoxList(ComboBoxOptions);
    }

    public class ComboBoxItem
    {
        public string ComboBoxOption { get; set; }
        public string ComboBoxHumanReadableOption { get; set; }
    }

    public class ComboBoxOptionsManager
    {
        public static void GetComboBoxList(ObservableCollection<ComboBoxItem> ComboBoxItems)
        {
            var allItems = getComboBoxItems();
            ComboBoxItems.Clear();
            allItems.ForEach(p => ComboBoxItems.Add(p));
        }

        private static List<ComboBoxItem> getComboBoxItems()
        {
            var items = new List<ComboBoxItem>();

            items.Add(new ComboBoxItem() { ComboBoxOption = "Option1", ComboBoxHumanReadableOption = "Option 1" });
            items.Add(new ComboBoxItem() { ComboBoxOption = "Option2", ComboBoxHumanReadableOption = "Option 2" });
            items.Add(new ComboBoxItem() { ComboBoxOption = "Option3", ComboBoxHumanReadableOption = "Option 3" });

            return items;
        }
    }


    string _SelectedComboBoxOption = "Option1";
    public string SelectedComboBoxOption
    {
        get
        {
            return _SelectedComboBoxOption;
        }
        set
        {
            if (_SelectedComboBoxOption != value)
            {
                _SelectedComboBoxOption = value;
                RaisePropertyChanged("SelectedComboBoxOption");
            }
        }
    }

    void RaisePropertyChanged(string prop)
    {
        if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(prop)); }
    }
    public event PropertyChangedEventHandler PropertyChanged;
 }
}

Answer 1

正如@Mike Eason和@kubakista所说，你需要明确地设置Mode。但这不会完全解决你的问题。

在您的代码中，您的SelectedComboBoxOption是一个字符串，但SelectedItem是一个ComboBoxItem对象。绑定String到SelectedItem不会更改ComboBox所选项目。因此，如果您想使用SelectedComboBoxOption来获取和设置ComboBox所选项目，则需要将SelectedComboBoxOption更改为ComboBoxItem并使用转换为{{ 1}}在{x:Bind}和Object之间进行转换。

转化可能会像：

ComboBoxItem

XAML可能会喜欢：

public class ComboBoxItemConvert : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
        return value as MainPage.ComboBoxItem;
    }
}

在代码隐藏中：

<Page ...>
    <Page.Resources>
        <local:ComboBoxItemConvert x:Key="ComboBoxItemConvert" />
    </Page.Resources>

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <StackPanel>
            <ComboBox Name="ComboBox"
                      DisplayMemberPath="ComboBoxHumanReadableOption"
                      Header="ComboBox"
                      ItemsSource="{x:Bind ComboBoxOptions}"
                      SelectedItem="{x:Bind SelectedComboBoxOption, Mode=TwoWay, Converter={StaticResource ComboBoxItemConvert}}"
                      SelectedValuePath="ComboBoxOption" />
            <TextBlock Name="BoundTextblock" Text="{x:Bind SelectedComboBoxOption.ComboBoxHumanReadableOption, Mode=OneWay}" />
        </StackPanel>
    </Grid>
</Page>

如果您只想在public sealed partial class MainPage : Page, INotifyPropertyChanged { private ObservableCollection<ComboBoxItem> ComboBoxOptions; public MainPage() { this.InitializeComponent(); ComboBoxOptions = new ObservableCollection<ComboBoxItem>(); ComboBoxOptionsManager.GetComboBoxList(ComboBoxOptions); SelectedComboBoxOption = ComboBoxOptions[0]; } ... private ComboBoxItem _SelectedComboBoxOption; public ComboBoxItem SelectedComboBoxOption { get { return _SelectedComboBoxOption; } set { if (_SelectedComboBoxOption != value) { _SelectedComboBoxOption = value; RaisePropertyChanged("SelectedComboBoxOption"); } } } ... }中显示所选项目，则可以轻松实现。我们可以将TextBlock TextBlock属性绑定到Text＆＃39; s ComboBox。请注意，SelectedItem的类型为SelectedItem，System.Object为强类型，并将解析路径中每个步骤的类型。如果返回的类型没有该成员，则它将在编译时失败。所以我们需要指定一个强制转换来告诉绑定对象的真实类型。但是在{x:Bind}中投射嵌套类时会有issue。我们可以{x:Bind} ComboBoxItem作为解决方法。

MainPage

在XAML中：

namespace ComboBoxTest
{
    public class ComboBoxItem
    {
        public string ComboBoxOption { get; set; }
        public string ComboBoxHumanReadableOption { get; set; }
    }

    public sealed partial class MainPage : Page, INotifyPropertyChanged
    {
        ...
    }
}

Answer 2

默认情况下，x:Bind设置为OneTime。您只需将模式设置为OneWay即可解决此问题。

Text="{x:Bind SelectedComboBoxOption, Mode=OneWay}"

Answer 3

另一种解决方案（类似于MVVM）是在代码隐藏中创建ComboBoxItem类型的对象，绑定到该对象，然后让代码隐藏对对象进行操作以获取所需的字符串。这将使您不必创建转换器：

C#
public ComboBoxItem ComboBoxItemSelected {get; set;}

XAML
SelectedItem = "{Binding ComboBoxItemSelected, Mode=TwoWay}"

UWP Combobox绑定到SelectedItem属性

3 个答案: