[Silverlight]简单实现DataGrid使用CheckBox选择行

以前写过几个方法实现这个功能，但最终还是选择了不继承DataGrid，所以再重新发布出来。

先显示最终结果，其中左边是错误的例子，右边才是正确的

在DataGrid中使用CheckBox选择行时典型的错误就是CheckBox没有Binding到任何属性上，这样的话当拖动滚动条时CheckBox.IsChecked就会乱掉，如Demo中左边那个DataGrid所示。最直观的解决方法是禁用DataGrid的滚动条，或者在绑定的数据上添加一个用于绑定CheckBox的bool属性。
其实只要在DataGrid.LoadingRow事件中将CheckBox的DataContext设定为另外一个Object，就不需要牺牲DataGrid的高效能，也不需要改变原有数据的结构。最终的实现方法是自定义一个包含DataGrid的DataGridTemplateColumn，而不需要重写DataGrid，这样的坏处就是每次调用需要多写一局代码，如果不想这样就继承DataGrid然后把这句代码写进去。在DataGrid.Columns中加入自定义的Column,然后在代码中关联DataGrid和这个Colum，就完成了：

 <sdk:DataGrid ItemsSource="{Binding}"

                      AutoGenerateColumns="False"

                      Grid.Column="1"

                      x:Name="TestDataGrid">

            <sdk:DataGrid.Columns>

                <local:DataGridSelectColumn />

                <sdk:DataGridTextColumn Header="Name"

                                        Binding="{Binding Name}"

                                        Width="*" />

            </sdk:DataGrid.Columns>

        </sdk:DataGrid>

   TestDataGrid.EnableSelect();

下面是这个DataGridSelectColumn的具体实现。创建一个UserControl然后把它改成DataGridTemplateColumn，这样好处是DataTemplate和Style中的FrameworkElement都可以轻松地获取。

<sdk:DataGridTemplateColumn xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"

                            x:Class="DataGridSelectSample.DataGridSelectColumn"

                            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"

                            mc:Ignorable="d" 

                            d:DesignHeight="300"

                            d:DesignWidth="400">

    <sdk:DataGridTemplateColumn.HeaderStyle>

        <Style TargetType="ContentControl">

            <Setter Property="ContentTemplate">

                <Setter.Value>

                    <DataTemplate>

                        <CheckBox  Content="Select All"

                                   VerticalContentAlignment="Center"

                                   VerticalAlignment="Center"

                                   Loaded="OnHeaderCheckBoxLoaded"/>

                    </DataTemplate>

                </Setter.Value>

            </Setter>

        </Style>

    </sdk:DataGridTemplateColumn.HeaderStyle>

    <sdk:DataGridTemplateColumn.CellTemplate>

        <DataTemplate>

            <CheckBox IsChecked="{Binding IsSelected,Mode=TwoWay}"

                      VerticalAlignment="Center"

                      HorizontalAlignment="Center" />

        </DataTemplate>

    </sdk:DataGridTemplateColumn.CellTemplate>

</sdk:DataGridTemplateColumn>

public partial class DataGridSelectColumn : DataGridTemplateColumn

    {



        private DataGrid _ownerDataGrid;

        private CheckBox _headerCheckBox;

        private Dictionary<object, MarkObject> _markObjects;



        public event EventHandler SelectedItemChanged;



        public DataGridSelectColumn()

        {

            InitializeComponent();

            IsReadOnly = true;

            _markObjects = new Dictionary<object, MarkObject>();

        }



        public DataGrid OwnerDataGrid

        {

            get { return _ownerDataGrid; }

            set

            {

                _ownerDataGrid = value;

                _ownerDataGrid.LoadingRow += OnLoadingRow;

            }

        }



        public void SelecteAll()

        {

            if (_headerCheckBox != null)

                _headerCheckBox.IsChecked = true;

            SetAllSelectedStates(true);

        }



        public void UnselectAll()

        {

            if (_headerCheckBox != null)

                _headerCheckBox.IsChecked = false;

            SetAllSelectedStates(false);

        }



        public List<T> GetSelectedItems<T>()

        {

            List<T> result = new List<T>();

            if (_ownerDataGrid.ItemsSource != null)

            {

                var enu = _ownerDataGrid.ItemsSource.GetEnumerator();

                while (enu.MoveNext())

                {

                    if (GetMarkObject(enu.Current).IsSelected)

                        result.Add((T)enu.Current);

                }

            }

            ClearItems();

            return result;

        }



        public void SetSelectedItems(IList items)

        {

            if (_ownerDataGrid.ItemsSource == null)

                return;



            var enu = _ownerDataGrid.ItemsSource.GetEnumerator();

            while (enu.MoveNext())

            {

                GetMarkObject(enu.Current).IsSelected = items.Contains(enu.Current);

            }

        }



        private void ClearItems()

        {

            var enu = _ownerDataGrid.ItemsSource.GetEnumerator();

            List<object> list = new List<object>();

            while (enu.MoveNext())

            {

                list.Add(enu.Current);

            }

            List<object> removableObjects = new List<object>();

            foreach (var item in _markObjects)

            {

                if (list.Contains(item.Key) == false)

                {

                    removableObjects.Add(item.Key);

                }

            }

            for (int i = 0; i < removableObjects.Count; i++)

            {

                _markObjects.Remove(removableObjects[i]);

            }

        }



        private void OnHeaderCheckBoxLoaded(object sender, RoutedEventArgs e)

        {

            _headerCheckBox = sender as CheckBox;

            _headerCheckBox.Loaded -= OnHeaderCheckBoxLoaded;

            _headerCheckBox.Checked += (s2, e2) => SetAllSelectedStates(true);

            _headerCheckBox.Unchecked += (s2, e2) => SetAllSelectedStates(false);

        }



        private void OnLoadingRow(object sender, DataGridRowEventArgs e)

        {

            object dataContext = e.Row.DataContext;

            FrameworkElement element = this.GetCellContent(e.Row);

            element.DataContext = GetMarkObject(dataContext);

        }



        private void SetAllSelectedStates(bool value)

        {

            if (_ownerDataGrid.ItemsSource == null)

                return;



            var enu = _ownerDataGrid.ItemsSource.GetEnumerator();

            while (enu.MoveNext())

            {

                GetMarkObject(enu.Current).IsSelected = value;

            }

            ClearItems();

        }



        private MarkObject GetMarkObject(Object obj)

        {

            if (_markObjects.ContainsKey(obj) == false)

            {

                MarkObject markObject;

                markObject = new MarkObject();

                _markObjects.Add(obj, markObject);

                markObject.PropertyChanged += (s, e) =>

                {

                    if (e.PropertyName == "IsSelected")

                    {

                        if (SelectedItemChanged != null)

                        {

                            SelectedItemChanged(this, EventArgs.Empty);

                        }

                    }

                };

            }



            return _markObjects[obj];

        }

    }

其中MarkObject是一个继承INotifyPropertyChanged的类,包含Selected属性，这样更改IsSelected时可以更新UI。

最后加上DataGridExtensions 是为了方便调用。

 

  public static class DataGridExtensions

    {

        internal static DataGridSelectColumn GetSelectColumn(this DataGrid dataGrid)

        {

            DataGridSelectColumn result = null;

            for (int i = 0; i < dataGrid.Columns.Count; i++)

            {

                result = dataGrid.Columns[i] as DataGridSelectColumn;

                if (result != null)

                    break;

            }

            return result;

        }



        public static void EnableSelect(this DataGrid dataGird)

        {

            var column = GetSelectColumn(dataGird);

            column.OwnerDataGrid = dataGird;

        }



        public static void SelectAll(this DataGrid dataGrid)

        {

            DataGridSelectColumn column = GetSelectColumn(dataGrid);

            if (column == null)

                throw new Exception("No Select Column");

            column.SelecteAll();

        }



        public static void UnselectAll(this DataGrid dataGrid)

        {

            DataGridSelectColumn column = GetSelectColumn(dataGrid);

            if (column == null)

                throw new Exception("No Select Column");

            column.UnselectAll();

        }



        public static List<T> GetSelectedItems<T>(this DataGrid dataGrid)

        {

            DataGridSelectColumn column = GetSelectColumn(dataGrid);

            if (column == null)

                throw new Exception("No Select Column");

            return column.GetSelectedItems<T>();

        }



        public static void SetSelectedItems(this DataGrid dataGrid, IList items)

        {

            DataGridSelectColumn column = GetSelectColumn(dataGrid);

            if (column == null)

                throw new Exception("No Select Column");

            column.SetSelectedItems(items);

        }

    }

附上完整源码，欢迎指正。

/Files/dino623/DataGridSelectSample.zip