数据绑定(十)Binding的数据转换
当Source端Path所关联的数据与Target端目标属性数据类型不一致时,需要添加数据转换器,数据转换器是一个自定义的类,这个类需要实现IValueConverter接口,这个接口有两个方法需要实现:Convert和ConvertBack,当数据从Source流向Target时,将调用Convert方法,反之,将调用ConvertBack方法
例子,首先定义飞机类型
- public enum Category
- {
- Bomber,
- Fighter
- }
- public enum State
- {
- Available,
- Locked,
- Unknown
- }
- public class Plane
- {
- public Category Category { get; set; }
- public string Name { get; set; }
- public State State { get; set; }
- }
Plane类型的Category将在界面上转换为图片,而State类型将会转换成界面上的CheckBox显示,由于存在两个转换,因此需要提供两个Converter,第一个转换是做Category类型与字符类型的转换,字符串是图片的路径
- class CategoryToSourceConverter : IValueConverter
- {
- public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
- {
- Category c = (Category)value;
- switch (c)
- {
- case Category.Bomber:
- {
- return @"\Icons\close.png";
- }
- case Category.Fighter:
- {
- return @"\Icons\closeing.png";
- }
- default:
- {
- return null;
- }
- }
- }
- public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
- {
- return new NotImplementedException();
- }
- }
由于UI上不能修改图片,所以只实现了从Source到Target的转换
另一个转换用于将State数据转换为bool?
- public class StateToNullableBoolConverter : IValueConverter
- {
- public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
- {
- State s = (State)value;
- switch (s)
- {
- case State.Locked:
- {
- return false;
- }
- case State.Available:
- {
- return true;
- }
- case State.Unknown:
- default:
- {
- return null;
- }
- }
- }
- public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
- {
- bool? nb = (bool?)value;
- switch (nb)
- {
- case true:
- {
- return State.Available;
- }
- case false:
- {
- return State.Locked;
- }
- case null:
- default:
- {
- return State.Unknown;
- }
- }
- }
- }
界面代码:
- <Window x:Class="WpfApplication1.MainWindow"
- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
- xmlns:local="clr-namespace:WpfApplication1"
- Title="MainWindow" Height="275" Width="275">
- <strong> <Window.Resources>
- <local:CategoryToSourceConverter x:Key="cts" />
- <local:StateToNullableBoolConverter x:Key="stnb" />
- </Window.Resources></strong>
- <StackPanel Background="LightBlue">
- <ListBox x:Name="listBoxPlane" Height="160" Margin="5">
- <ListBox.ItemTemplate>
- <DataTemplate>
- <StackPanel Orientation="Horizontal">
- <strong> <Image Width="20" Height="20" Source="{Binding Path=Category, Converter={StaticResource cts}}" />
- <TextBlock Text="{Binding Path=Name}" Width="60" Margin="80,0" />
- <CheckBox IsThreeState="True" IsChecked="{Binding Path=State, Converter={StaticResource stnb}}" /></strong>
- </StackPanel>
- </DataTemplate>
- </ListBox.ItemTemplate>
- </ListBox>
- <Button x:Name="buttonLoad" Content="Load" Height="25" Margin="5,0" Click="buttonLoad_Click" />
- <Button x:Name="buttonSave" Content="Save" Height="25" Margin="5,0" Click="buttonSave_Click" />
- </StackPanel>
- </Window>
加粗的部分是XAML中对转换器的使用,后台代码中实现了Load和Save两个按钮的点击事件
- private void buttonLoad_Click(object sender, RoutedEventArgs e)
- {
- List<Plane> planeList = new List<Plane>()
- {
- new Plane(){Category=Category.Bomber, Name="B-1", State=State.Unknown},
- new Plane(){Category=Category.Bomber, Name="B-2", State=State.Unknown},
- new Plane(){Category=Category.Fighter, Name="F-22", State=State.Unknown},
- new Plane(){Category=Category.Fighter, Name="Su-47", State=State.Unknown},
- new Plane(){Category=Category.Bomber, Name="B-52", State=State.Unknown},
- new Plane(){Category=Category.Fighter, Name="J-10", State=State.Unknown}
- };
- listBoxPlane.ItemsSource = planeList;
- }
- private void buttonSave_Click(object sender, RoutedEventArgs e)
- {
- StringBuilder sb = new StringBuilder();
- foreach (Plane p in listBoxPlane.Items)
- {
- sb.AppendLine(string.Format("Category={0}, Name={1}, State={2}", p.Category, p.Name, p.State));
- }
- File.WriteAllText(@"d:\PlaneList.txt", sb.ToString());
- }
界面效果如图:
当改变checkbox的选中状态时,Plane对象中的值会发生变化
posted on 2017-07-26 09:18 alex5211314 阅读(154) 评论(0) 编辑 收藏 举报