如何使用Wpf mvvm在下拉列表中启用/禁用复选框值并在文本框中显示多选值

using System.Collections.ObjectModel;
using System.Windows.Input;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;

namespace YourNamespace
{
    public class ViewModel : ViewModelBase
    {
        public ObservableCollection<CheckBoxItem> CheckBoxItems { get; set; }

        private string selectedValues;
        public string SelectedValues
        {
            get { return selectedValues; }
            set { Set(ref selectedValues, value); }
        }

        public ICommand CheckBoxCommand { get; private set; }

        public ViewModel()
        {
            CheckBoxItems = new ObservableCollection<CheckBoxItem>
            {
                new CheckBoxItem { Value = "Value 1", IsChecked = false },
                new CheckBoxItem { Value = "Value 2", IsChecked = false },
                new CheckBoxItem { Value = "Value 3", IsChecked = false }
            };

            CheckBoxCommand = new RelayCommand<CheckBoxItem>(CheckBoxCommandExecute);
        }

        private void CheckBoxCommandExecute(CheckBoxItem item)
        {
            item.IsChecked = !item.IsChecked;

            SelectedValues = string.Empty;
            foreach (var checkBoxItem in CheckBoxItems)
            {
                if (checkBoxItem.IsChecked)
                {
                    SelectedValues += checkBoxItem.Value + ", ";
                }
            }
            SelectedValues = SelectedValues.TrimEnd(',', ' ');
        }
    }

    public class CheckBoxItem
    {
        public string Value { get; set; }
        public bool IsChecked { get; set; }
    }
}

<Window x:Class="YourNamespace.View"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:YourNamespace"
        Title="Your Application" Height="450" Width="800">
    <Window.DataContext>
        <local:ViewModel />
    </Window.DataContext>
    <Grid>
        <ComboBox ItemsSource="{Binding CheckBoxItems}"
                  DisplayMemberPath="Value"
                  SelectedValuePath="IsChecked"
                  SelectedValue="{Binding SelectedValues, Mode=TwoWay}"
                  SelectionChanged="ComboBox_SelectionChanged"
                  IsEditable="True"
                  IsReadOnly="True"
                  IsDropDownOpen="False"
                  IsDropDownOpen="{Binding IsDropDownOpen, Mode=TwoWay}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <CheckBox Content="{Binding Value}"
                              IsChecked="{Binding IsChecked}"
                              Command="{Binding DataContext.CheckBoxCommand, RelativeSource={RelativeSource AncestorType=ComboBox}}"
                              CommandParameter="{Binding}" />
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
        <TextBox Text="{Binding SelectedValues}" Margin="10,30,10,10" />
    </Grid>
</Window>