wpf GridControl selectAll UnSelect

<Window x:Class="WpfApplication1.GridControlView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid" 
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
        xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
        Title="GridControlView" >
    <Grid>
        <StackPanel>
            <Button Click="BtnInvert_Click">Invert selection</Button>
            <Button Click="BtnGetSelected_Click">Get selection</Button>
            <dxg:GridControl x:Name="grid" CustomUnboundColumnData="grid_CustomUnboundColumnData" Height="500" ItemsSource="{Binding List}">
                <dxg:GridControl.Columns>
                    <dxg:GridColumn FieldName="Id" />
                    <dxg:GridColumn FieldName="Number" />
                    <dxg:GridColumn FieldName="Selected" UnboundType="Boolean" AllowSorting="False">
                        <dxg:GridColumn.CellTemplate>
                            <DataTemplate>
                                <dxe:CheckEdit IsChecked="{Binding Data.Selected}" HorizontalAlignment="Center" VerticalAlignment="Center" />
                            </DataTemplate>
                        </dxg:GridColumn.CellTemplate>
                    </dxg:GridColumn>
                </dxg:GridControl.Columns>
                <dxg:GridControl.View>
                    <dxg:TableView x:Name="view" AutoWidth="True" />
                </dxg:GridControl.View>
            </dxg:GridControl>
        </StackPanel>
    </Grid>
</Window>

/// <summary>
    /// GridControlView.xaml 的交互逻辑
    /// </summary>
    public partial class GridControlView : Window
    {
        public GridControlView()
        {
            InitializeComponent();
            //Dxsl.LoginManage.ViewModels.LookupControlViewModel viewModel = new Dxsl.LoginManage.ViewModels.LookupControlViewModel();

            //this.DataContext = viewModel;
            DataContext = data;
        }

        TestData data = new TestData();
        SelectionHelper<Guid> selectionHelper = new SelectionHelper<Guid>();

        /// <summary>
        /// Grid触发事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void grid_CustomUnboundColumnData(object sender, GridColumnDataEventArgs e)
        {
            if (e.Column.FieldName != "Selected") return;
            Guid key = (Guid)e.GetListSourceFieldValue("Id");
            if (e.IsGetData)
                e.Value = selectionHelper.GetIsSelected(key);
            if (e.IsSetData)
                selectionHelper.SetIsSelected(key, (bool)e.Value);
        }
        /// <summary>
        /// 全选或者反选
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void BtnInvert_Click(object sender, RoutedEventArgs e)
        {
            for (int i = 0; i < data.List.Count; i++)
            {
                int rowHandle = this.grid.GetRowHandleByListIndex(i);
                bool newIsSelected = !selectionHelper.GetIsSelected(data.List[i].Id);
                grid.SetCellValue(rowHandle, "Selected", newIsSelected);
            }
        }
        /// <summary>
        /// 获取选中项
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void BtnGetSelected_Click(object sender, RoutedEventArgs e)
        {
            string caption = string.Format("Selected rows (Total: {0})", selectionHelper.GetSelectionCount());
            MessageBox.Show(selectionHelper.GetSelectedKeysAsString(), caption);
        }
    }

 /// <summary>
    /// 选择帮助类
    /// </summary>
    /// <typeparam name="KeyType">类型</typeparam>
    public class SelectionHelper<KeyType>
    {
        /// <summary>
        /// 选中集合字典
        /// </summary>
        Dictionary<KeyType, bool> selectedValues = new Dictionary<KeyType, bool>();
        /// <summary>
        /// 获取key是否被选中
        /// </summary>
        /// <param name="key">key 值</param>
        /// <returns></returns>
        public bool GetIsSelected(KeyType key)
        {
            //声明是否选择变量,默认为false
            bool isSelected;
            if (selectedValues.TryGetValue(key, out isSelected))
                return isSelected;
            return false;
        }
        /// <summary>
        /// 设置选中项的值
        /// </summary>
        /// <param name="key">key 值</param>
        /// <param name="value">true or false</param>
        public void SetIsSelected(KeyType key, bool value)
        {
            if (value)
                selectedValues[key] = value;
            else
                selectedValues.Remove(key);
        }
        /// <summary>
        /// 获取集合字典中的选中项
        /// </summary>
        /// <returns></returns>
        public List<KeyType> GetSelectedKeys()
        {
            List<KeyType> list = new List<KeyType>();
            //遍历集合
            foreach (KeyType key in selectedValues.Keys)
                list.Add(key);
            return list;
        }
        /// <summary>
        /// 获取集合中项 加入StringBuilder 仅测试用
        /// </summary>
        /// <returns></returns>
        public string GetSelectedKeysAsString()
        {
            List<KeyType> list = GetSelectedKeys();
            StringBuilder str = new StringBuilder();
            for (int i = 0; i < list.Count; i++)
                str.AppendLine(list[i].ToString());
            return str.ToString();
        }
        /// <summary>
        /// 获取选择数量
        /// </summary>
        /// <returns></returns>
        public int GetSelectionCount()
        {
            return selectedValues.Count;
        }
    }

    public class TestData
    {
        public List<TestDataItem> List { get; private set; }
        public TestData()
        {
            List<TestDataItem> list = new List<TestDataItem>();
            for (int i = 0; i < 20; i++)
            {
                list.Add(new TestDataItem() { Id = Guid.NewGuid(), Number = i });
            }
            List = list;
        }
    }

    public class TestDataItem
    {
        public Guid Id { get; set; }
        public int Number { get; set; }
    }