Question

我正在使用DevExpress ComboboxEdit对象从用户那里获得多个选择。我的问题是，我不确定选择完成后会回来什么类型的对象。

我已阅读this one，并提出了以下代码，但我不确定我错过了什么。（我也不确切知道DependencyProperty是什么，但是想避免太多的对象）

<Window x:Class = "Demo.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:Demo"
             xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
             xmlns:dxl="http://schemas.devexpress.com/winfx/2008/xaml/layoutcontrol"
             xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
   mc:Ignorable = "d"
   Title = "MainWindow" Height = "350" Width = "525">

    <StackPanel>

        <dxe:ComboBoxEdit ItemsSource="{Binding Path=MyList}"
                          IsTextEditable="False"
                          EditValue="{Binding Path=MySelectedList, Mode=TwoWay}"
                          Name="abc">
            <dxe:ComboBoxEdit.StyleSettings>
                <dxe:CheckedComboBoxStyleSettings/>
            </dxe:ComboBoxEdit.StyleSettings>
        </dxe:ComboBoxEdit>

        <Button Click="showSelected" Content="Show selected items" />

    </StackPanel>

</Window>

MainWindow.xaml.cs

using System.Collections.Generic;
using System.Windows;
using System.Text;

namespace Demo
{

    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        private System.Collections.Generic.IList<string> _myList;
        private System.Collections.Generic.IList<string> _mySelectedList; // This has probably the wrong type.

        public event PropertyChangedEventHandler PropertyChanged;

        protected void RaisePropertyChanged(string propertyName)
        {
            var handler = this.PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }


        public IList<string> MyList
        {
            get
            {
                return _myList;
            }

            set
            {
                _myList = value;
                this.RaisePropertyChanged("MyList");
            }
        }

        public IList<string> MySelectedList
        {
            get
            {
                return _mySelectedList;
            }

            set
            {
                _mySelectedList = value;
                this.RaisePropertyChanged("MySelectedList");
            }
        }

        private void showSelected(object sender, RoutedEventArgs e)
        {
            StringBuilder sb = new StringBuilder();
            foreach(string s in this.MySelectedList)
            {
                sb.Append(s);
            }
            System.Windows.MessageBox.Show(sb.ToString());
            // This MessageBox show show whatever is checked.
        }

        public MainWindow()
        {
            MySelectedList = new System.Collections.Generic.List<string>();

            MyList = new System.Collections.Generic.List<string>();
            MyList.Add("a");
            MyList.Add("b");
            MyList.Add("c");
            MyList.Add("d");

            DataContext = this;
        }
    }
}

当我运行它并点击组合框时，会出现一个红色X，并显示The type System.Collection.Generic.List´1[System.Object] could not be converted。 MessageBox总是空的。

Answer 1

您的MainWindow未实施INotifyPropertyChanged，但这可能不是唯一的问题。在你真正尝试修补WPF之前，我会在Dependency Properties和Data Binding上阅读。如果你不理解这些概念，一切都会变得困难和困惑。

修改

他们似乎正在使用DependencyProperty（正如您所提到的）。但无论如何，这就是你实现一个
的方法
public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.Register("SelectedItems", typeof(IList), typeof(MainWindow), new PropertyMetadata(null, new PropertyChangedCallback(OnSelectedItemsChanged))); private static void OnSelectedItemsChanged(DependencyObject o, DependencyPropertyChangedEventArgs e) { MainWindow mainWindow = o as MainWindow; if (mainWindow != null) mainWindow.OnSelectedItemsChanged((IList)e.OldValue, (IList)e.NewValue); } protected virtual void OnSelectedItemsChanged(IList oldValue, IList newValue) { // Add your property changed side-effects. Descendants can override as well. } public IList SelectedItems { // IMPORTANT: To maintain parity between setting a property in XAML and procedural code, do not touch the getter and setter inside this dependency property! get { return (IList)GetValue(SelectedItemsProperty); } set { SetValue(SelectedItemsProperty, value); } }

请注意，它必须是IList类型，您需要转换为string
类型
另外，删除绑定中不需要的Mode=TwoWay。

<dxe:ComboBoxEdit ItemsSource="{Binding MyList}" EditValue="{Binding SelectedItems}" > <dxe:ComboBoxEdit.StyleSettings> <dxe:CheckedComboBoxStyleSettings/> </dxe:ComboBoxEdit.StyleSettings> </dxe:ComboBoxEdit>

您也不需要INotifyPropertyChanged这是我的错误。我以为你在做传统的装订。

Answer 2

EditValue属性包含对象列表，因此VM中的代码应如下所示：

private List<object> _mySelectedList;

public List<object> MySelectedList
{
    get
    {
        return _mySelectedList;
    }

    set
    {
        _mySelectedList = value;
        this.RaisePropertyChanged("MySelectedList");
    }
}

或者您可以编写EditValue转换器，例如，您会找到here。

从dxe：ComboBoxEdit中获取选定的值

2 个答案: