Windows Phone MultiBinding ：Cimbalino Toolkit

在WPF和WIN8中是支持MultiBinding

这个有啥用呢，引用下MSDN的例子http://msdn.microsoft.com/en-us/library/system.windows.data.multibinding.aspx：

MultiBinding allows you to bind a binding target property to a list of source properties and then apply logic to produce a value with the given inputs. This example demonstrates how to use MultiBinding.

In the following example, NameListData refers to a collection of PersonName objects, which are objects that contain two properties, firstName and lastName. The following example produces a TextBlock that shows the first and last names of a person with the last name first.

<TextBlock Name="textBox2" DataContext="{StaticResource NameListData}">

  <TextBlock.Text>

    <MultiBinding Converter="{StaticResource myNameConverter}"

                  ConverterParameter="FormatLastFirst">

      <Binding Path="FirstName"/>

      <Binding Path="LastName"/>

    </MultiBinding>

  </TextBlock.Text>

</TextBlock>

 

public class NameConverter : IMultiValueConverter

{

    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)

    {

        string name;

        switch ((string)parameter)

        {

            case "FormatLastFirst":

                name = values[1] + ", " + values[0];

                break;

            case "FormatNormal":

            default:

                name = values[0] + " " + values[1];

                break;

        }

        return name;

    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)

    {

        string[] splitValues = ((string)value).Split(' ');

        return splitValues;

    }

}

可惜在wp中这个被砍掉了

想要 MultiBinding 需要自己来实现（方法见高手博客：http://www.devdiv.com/wp_amp_win_-blog-55433-51080.html）

当然也有一个稍微简单点的方法，使用Cimbalino Windows Phone Toolkit（http://cimbalino.org/），Cimbalino Toolkit 的作者为我们提供了一个MultiBindingBehavior，可以比较方便的实现 MultiBinding

下面看一个实例把，这里我们模拟一个显示学生各科成绩的应用，在应用中有一个ListPicker，应用会根据ListPicker的值来作为阈值，对成绩的颜色进行修改，下面是实现:

我们先新建一个wp工程（7.1，8.0都行，Cimbalino toolkit is compatible with the Windows Phone SDK 7.1.x and Windows Phone 8.0，这里我用7.1的，主要是机器不行，8.0的模拟器太卡…）

添加成绩类：

namespace PhoneIValueConverterMultibinding1

{

    public class Score

    {

        public string name { get; set; }

        public int number { get; set; }

    }

}

在工程中添加Cimbalino Windows Phone Toolkit

然后定义我们的颜色转换类（由于我没用双向绑定，所以没写ConvertBack…）：

using System;

using System.Windows.Media;

using System.Globalization;

using Cimbalino.Phone.Toolkit.Converters;

namespace PhoneIValueConverterMultibinding1

{

    public class ColorChange : MultiValueConverterBase 

    {

        public override object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)

        {

            if (values.Length < 2)

            {

                return new SolidColorBrush(Colors.White);

            }

            if ((values[0] != null) && (values[1] != null))

            {

                //根据输入，判断返回值

                try

                {

                    int limitnumber = System.Convert.ToInt32((string)values[0]);

                    int studentscore = (int)values[1];

                    if (limitnumber < studentscore)

                    {

                        return new SolidColorBrush(Colors.Red);

                    }

                    else

                    {

                        return new SolidColorBrush(Colors.Green);

                    }

                }

                catch (FormatException)

                {

                    return new SolidColorBrush(Colors.White);

                }

                catch (Exception)

                {

                    return new SolidColorBrush(Colors.White);

                }

            }

            else

            {

                return new SolidColorBrush(Colors.White);

            }       

        }

        public override object[] ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

        {

            throw new NotImplementedException();

        }

    }

}

然后在xaml里添加引用：

    xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"

    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

    xmlns:Local="clr-namespace:PhoneIValueConverterMultibinding1"

    xmlns:cimbalinoBehaviors="clr-namespace:Cimbalino.Phone.Toolkit.Behaviors;assembly=Cimbalino.Phone.Toolkit"

添加ListPicker

                <toolkit:ListPicker Header="成绩阈值" Name="listpicker1" SelectionChanged="listpicker1_SelectionChanged">

                    <toolkit:ListPickerItem Content="50" />

                    <toolkit:ListPickerItem Content="60" />

                    <toolkit:ListPickerItem Content="70" />

                    <toolkit:ListPickerItem Content="80" />

                    <toolkit:ListPickerItem Content="90" />

                </toolkit:ListPicker>

添加页面资源

    <phone:PhoneApplicationPage.Resources>
        <Local:ColorChange x:Key="ColorConverter" />
    </phone:PhoneApplicationPage.Resources>

然后添加绑定的listbox，并在其中添加MultiBindingBehavior ，因为我们要改变的是文字的颜色，所以设置PropertyName="Foreground"

                <ListBox Height="510" Name="lb1" Margin="12,12,0,0" >

                    <ListBox.ItemTemplate>

                        <DataTemplate>

                            <StackPanel Width="432" Orientation="Horizontal">

                                <TextBlock TextWrapping="Wrap" Text="{Binding name}" FontSize="32" Width="200" />

                                <TextBlock TextWrapping="Wrap" Text="{Binding number}" FontSize="32" Margin="0" >

                                        <i:Interaction.Behaviors>

                                            <cimbalinoBehaviors:MultiBindingBehavior Converter="{StaticResource ColorConverter}" PropertyName="Foreground"  >                                                

                                                <cimbalinoBehaviors:MultiBindingItem Value="{Binding ElementName=listpicker1, Path=SelectedItem.Content}" />             

                                                <cimbalinoBehaviors:MultiBindingItem Value="{Binding number}" />

                                            </cimbalinoBehaviors:MultiBindingBehavior>

                                        </i:Interaction.Behaviors>

                                </TextBlock>

                            </StackPanel>

                        </DataTemplate>

                    </ListBox.ItemTemplate>                    

                </ListBox>

最后数据绑定：

        ObservableCollection<Score> StudentScore = new ObservableCollection<Score>();

        private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)

        {

            StudentScore.Add(new Score { name = "语文", number = 55 });

            StudentScore.Add(new Score { name = "数学", number = 66 });

            StudentScore.Add(new Score { name = "英语", number = 76 });

            StudentScore.Add(new Score { name = "物理", number = 72 });

            StudentScore.Add(new Score { name = "化学", number = 97 });

            StudentScore.Add(new Score { name = "生物", number = 86 });

            StudentScore.Add(new Score { name = "地理", number = 68 });

            StudentScore.Add(new Score { name = "历史", number = 95 });

            StudentScore.Add(new Score { name = "政治", number = 39 });

  }

        private void listpicker1_SelectionChanged(object sender, SelectionChangedEventArgs e)

        {

            if (listpicker1 != null)

            {

                if (listpicker1.SelectedIndex != -1)

                {

                    lb1.ItemsSource = StudentScore;

                }

            }            

        }

看看效果：

最后说下Ms强烈建议不要在复杂绑定中是使用Converter

另外Cimbalino Windows Phone Toolkit还有许多其他的功能

大家可以试试

源码：

参考：

http://msdn.microsoft.com/en-us/library/system.windows.data.multibinding.aspx

https://github.com/Cimbalino/Cimbalino-Phone-Toolkit

http://www.pedrolamas.com/2013/05/17/cimbalino-windows-phone-toolkit-multibindingbehavior/