WPF DataGrid Visibility的綁定

標籤：

　　情境：根據設定檔顯示DataGrid中的某些列。

　　問題：Columns集合只是DataGrid的一個屬性，這個集合在邏輯樹狀結構或視覺樹中是看不到的，也不會繼承DataContext屬性。

　　通過網上查閱各種資料，方法可以歸結以下幾種，下面將一一展示。

　　方法一：對DataGridColumn附加DataContext屬性

　　該方法需要用到一個協助類（需要建立一個全域執行個體），具體內容如下：

public class DataGridContextHelper    {        static DataGridContextHelper()        {            DependencyProperty dp = FrameworkElement.DataContextProperty.AddOwner(typeof(DataGridColumn));            FrameworkElement.DataContextProperty.OverrideMetadata(typeof(DataGrid),            new FrameworkPropertyMetadata               (null, FrameworkPropertyMetadataOptions.Inherits,               new PropertyChangedCallback(OnDataContextChanged)));        }        public static void OnDataContextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)        {            DataGrid grid = d as DataGrid;            if (grid != null)            {                foreach (DataGridColumn col in grid.Columns)                {                    col.SetValue(FrameworkElement.DataContextProperty, e.NewValue);                }            }        }    } 

　　前台綁定樣本

<DataGridTextColumn x:Name="col2" Header="TestColumn"                                    Visibility="{Binding (FrameworkElement.DataContext).Show,RelativeSource={RelativeSource Self},Converter={StaticResource cc}}"></DataGridTextColumn>

 

　　後台綁定樣本

var binding = new Binding();            binding.Mode = BindingMode.OneWay;            binding.RelativeSource=new RelativeSource(RelativeSourceMode.Self);            binding.Converter = new BooleanToVisibilityConverter();            binding.Path=new PropertyPath("(FrameworkElement.DataContext).Show");            BindingOperations.SetBinding(obj, DataGridColumn.VisibilityProperty, binding);

　　方法二：通過Source直接與Vm綁定

　　範例程式碼：

var binding = new Binding();            binding.Mode = BindingMode.OneWay;            binding.Source = vm;            binding.Converter = new BooleanToVisibilityConverter();            binding.Path = new PropertyPath("Show");            BindingOperations.SetBinding(obj, DataGridColumn.VisibilityProperty, binding);

 

　　方法三：通過Source與VM的一個代理類進行綁定

　　代理類

　　Freezable可以繼承DataContext即使它們不在視覺樹或邏輯樹狀結構中

public class BindingProxy : Freezable    {        #region Overrides of Freezable        protected override Freezable CreateInstanceCore()        {            return new BindingProxy();        }        #endregion        public object Data        {            get { return (object)GetValue(DataProperty); }            set { SetValue(DataProperty, value); }        }        public static readonly DependencyProperty DataProperty =            DependencyProperty.Register("Data", typeof(object),                                         typeof(BindingProxy));    }

　　前台綁定代碼

 <DataGrid x:Name="dg" HorizontalAlignment="Left" VerticalAlignment="Top" Height="253" Width="436" ItemsSource="{Binding Persons}"                  AutoGenerateColumns="False">            <DataGrid.Resources>                <dgTest:BindingProxy x:Key="proxy" Data="{Binding}"/>            </DataGrid.Resources>            <DataGrid.Columns>                <DataGridTextColumn x:Name="col1" Header="TestColumn" Binding="{Binding Name}"></DataGridTextColumn>                <DataGridTextColumn x:Name="col2" Header="TestColumn"                                    Visibility="{Binding (FrameworkElement.DataContext).Show,RelativeSource={RelativeSource Self},Converter={StaticResource cc}}"></DataGridTextColumn>                <DataGridTextColumn x:Name="col3" Header="TestColumn"                                    Visibility="{Binding Data.Show,Source={StaticResource proxy},Converter={StaticResource cc}}"></DataGridTextColumn>            </DataGrid.Columns>        </DataGrid>

 

　　方法四：通過一個代理控制項來實現

　　代理控制項與代理對象的解決方式類似，都是因為其可以繼承DataContext屬性，只是一個在邏輯樹狀結構中看的到，一個看不到。樣本如下：

<FrameworkElement x:Name="dummyElement" Visibility="Collapsed"/>    <DataGrid>        <DataGrid.Columns>            <DataGridTextColumn Header="Test"                                Binding="{Binding Name}"                                Visibility="{Binding DataContext.IsEnable,                                          Source={x:Reference dummyElement}}"/>        </DataGrid.Columns>    </DataGrid>

 

WPF DataGrid Visibility的綁定