黑马程序员---wpf学习笔记四---banding的那些事

------- Windows Phone 7手机开发、.Net培训、期待与您交流！ -------

 

一、WPF中,对控件做数据banding,可以方便的进行赋值和获得值的操作:

例如一:

<Grid> 
                <Slider Name="Slider1" HorizontalAlignment="Left" Margin="38,55,0,0" VerticalAlignment="Top" Height="19" Width="227"/> 
                <TextBox Text="{Binding Value,ElementName=Slider1}" HorizontalAlignment="Left" Height="23" Margin="38,101,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
</Grid>

显示结果:(可以通过slider来滑动，控制textbox值的显示)

例二:  为控件设置数据源:
 

1.a  New一个类的实例，给 要绑定的控件设定DataContext

  private void Window_Loaded(object sender, RoutedEventArgs e)
  {
                        Person person = new Person();
                        person.Age = 22;
                        person.Name = "Charles";
                        tbAge.DataContext = person;
                        tbName.DataContext = person;
 }
 public class Person
        { 
                public int Age { set; get; }
              public string Name { set; get; }
        }

 

1.b   XAML中设置数据绑定的控件属性

    <TextBox Name="tbName" ToolTip="{Binding Name}" HorizontalAlignment="Left" Height="23" Margin="80,162,0,0" TextWrapping="Wrap" Text="{Binding Name}" VerticalAlignment="Top" Width="120"/>
                <TextBox Name="tbAge" ToolTip="{Binding Age}" HorizontalAlignment="Left" Height="23" Margin="80,207,0,0" TextWrapping="Wrap" Text="{Binding Age}" VerticalAlignment="Top" Width="120"/>
                        <TextBlock Text="姓名" Width="30" Margin="39,163,434,125" />
                        <TextBlock Margin="38,207,435,81" Text="年龄" Width="30" />

显示效果：
 

   

      但是,此种做法,无法将从后台变化的值在界面体现;如果需要后台对象值变化,前台也变化,就使用【INotifyPropertyChanged】”属性变化通知”机制来实现.
  2.a修改类的定义(注意需要引入 System.ComponentModel)：

定义的类，需要继承INotifyPropertyChanged，并实现该接口方法，如下：

引入: using System.ComponentModel;

class Person : INotifyPropertyChanged
     {
                private int age;
                private string name;
                public int Age
                {
                        get { return age; }
                        set
                        {
                             this.age = value;
                                if (PropertyChanged != null)
                                {
                                        PropertyChanged(this, new PropertyChangedEventArgs("Age"));
                                }
                        }
                }
                public string Name
                {
                        get { return name; }
                        set {
                                this.name = value;
                                if (PropertyChanged != null)
                                {
                                        PropertyChanged(this, new PropertyChangedEventArgs("Name"));
                                }                                        
                        }
                }
                public event PropertyChangedEventHandler PropertyChanged;
}

    其他步骤同上述1.a\1.b,为看到效果，可以添加一个按钮来实现！

                    private void btAge_Click(object sender, RoutedEventArgs e)
                {
                        person.Age++;
                }

截图：

二、给单个控件逐一赋值还是给所有控件共有的父控件赋值（进行数据banding）之争：
     对控件上下文(DataContext)的指定,第一种:可以直接指定给控件,缺点是当控件多了,代码量相对来说就多来了;第二种:指定给其父控件,当不给子控件指定DataContext时,默认使用父控件的上下文,相对来说,代码简约.

如下:

采用第一种:

                        Person person = new Person();
                        person.Age = 22;
                        person.Name = "Charles";
                        tbAge.DataContext = person;
                        tbName.DataContext = person;

采用第二种:

Person person = new Person();
this.DataContext = person;(注意:this,指代当前窗体,也可以使用当前需要绑定上下文的共有父控件,如grid1.DataContext=person)

 

------- Windows Phone 7手机开发、.Net培训、期待与您交流！ -------

 

 

 

banding的其它学习，可以参考如下：
http://www.codesky.net/article/200808/130118.html
http://developer.51cto.com/art/200808/87103_4.htm