WPF 绑定表达式和绑定数据源(一)__wpf数据绑定

绑定：描述的是一种关系，同构某种关系将多个事物联系在一起。

页面对象的属性（必须是依赖属性）：目标 Target
需要显示在界面上做交互关联的数据对象：源 Source

<Window x:Class="WpfApp2.BindingDemo.Window1"
        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"
        xmlns:local="clr-namespace:WpfApp2.BindingDemo"
        mc:Ignorable="d"
        Title="Window1" Height="450" Width="800">
    <Grid>
        <TextBlock Text="{Binding Source=data,Path=value}"></TextBlock>
    </Grid>
</Window>
  //备注：
  //Text：目标
  //Source=data,Path=value   源：  也是绑定表达式

1、绑定表达式

Text="{Binding Source=data,Path=value}" :将页面对象的某个属性与数据源建立联系。

通过绑定可以将界面与数据逻辑进行隔离。

2、绑定数据源

1、指定方式：

Source、ElementName、DataContext、RelativeSource、Path、XPath
2、数据源类型
1）依赖对象作为数据源

<Window x:Class="WpfApp2.MainWindow"
        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"
        xmlns:local="clr-namespace:WpfApp2"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800" Name="window">
    <Grid>
        <StackPanel>
          <!--依赖对象绑定-->
        <TextBox Name="txt" Text="123"></TextBox>
            <TextBlock Text="{Binding ElementName= txt,Path=Text}"></TextBlock>
            <TextBlock Text="{Binding ElementName= window,Path=Title}"></TextBlock>


            <TextBlock  Text="Solider当前值："></TextBlock>
            <TextBlock  Text="{Binding  ElementName=slider,Path= Value}"></TextBlock>
            <Slider Width="200" Name="slider"  Minimum="5" Maximum="100" HorizontalAlignment="Left"></Slider>
            <TextBlock Text="Solider最小值："></TextBlock>
            <TextBlock Text="{Binding ElementName=slider,Path=Minimum}"></TextBlock>
        </StackPanel> 
    </Grid>
</Window>

2）普通数据类型或集合类型作为数据源

<Window.Resources>
        <sys:String x:Key="name">小明</sys:String>
        <x:Array x:Key="data" Type="sys:String">
            <sys:String>小刚</sys:String>
        </x:Array>
    </Window.Resources>
    
     <!--普通对象，集合对象绑定   开始-->
            <TextBlock Text="{Binding Source={StaticResource name}}"></TextBlock>
            <TextBlock Text="{Binding Source={StaticResource data},Path=[0]}"></TextBlock>
            <!--普通对象，集合对象绑定   结束-->

3）单个对象作为数据源，INotifyPropertyChanged
新建类：DataClass 继承 INotifyPropertyChanged

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WpfApp2
{
    public class DataClass : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler? PropertyChanged;
        private string  _Value;
        public string Value
        {
            get { return _Value; }
            set
            {
                _Value = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Value"));
            }

        }

    }
}

xaml代码：

<Window.Resources> 
        <local:DataClass Value="这是单个对象作为数据源，INotifyPropertyChanged  " x:Key="dataclass"></local:DataClass>
    </Window.Resources> 
<Window>
<!--单个对象作为数据源，INotifyPropertyChanged  开始-->
<TextBlock Text="{Binding Source={StaticResource dataclass},Path=Value}"></TextBlock>
<!--单个对象作为数据源，INotifyPropertyChanged  结束-->      
</Window>

xaml.cs 代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp2
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            Task.Run(() => {
                Task.Delay(2000).GetAwaiter().GetResult();
                this.Dispatcher.Invoke(() => {
                    (this.Resources["dataclass"] as DataClass).Value = "";
                });
            });
        }
    }
}

4）XmlDataProvider作为数据源
新建一个XML文件：【simple.xml】

<?xml version="1.0" encoding="iso-8859-1"?>
<breakfast_menu>
  <food attr="a1" prop="p1">
    <name>Belgian Waffles</name>
    <price>$5.95</price>
    <description>two of our famous Belgian Waffles with plenty of real maple syrup</description>
    <calories>650</calories>
  </food>
  <food attr="a2">
    <name>Strawberry Belgian Waffles</name>
    <price>$7.95</price>
    <description>light Belgian waffles covered with strawberries and whipped cream</description>
    <calories>900</calories>
  </food>
  <food attr="a3">
    <name>Berry-Berry Belgian Waffles</name>
    <price>$8.95</price>
    <description>light Belgian waffles covered with an assortment of fresh berries and whipped cream</description>
    <calories>900</calories>
  </food>
  <food attr="a4">
    <name>French Toast</name>
    <price>$4.50</price>
    <description>thick slices made from our homemade sourdough bread</description>
    <calories>600</calories>
  </food>
  <food attr="a5">
    <name>Homestyle Breakfast</name>
    <price>$6.95</price>
    <description>two eggs, bacon or sausage, toast, and our ever-popular hash browns</description>
    <calories>950</calories>
  </food>
</breakfast_menu>

xaml 代码如下：

//d第一种读取方式   读取对象属性<Window.Resources>         <XmlDataProvider x:Key="xmlData" Source="pack://application:,,,/WpfApp2;component/simple.xml" XPath="breakfast_menu/food[1]"> </XmlDataProvider>    </Window.Resources>            <Window>    <!--xml  数据绑定 开始-->    <TextBlock Text="{Binding Source={StaticResource xmlData},XPath= name}"></TextBlock>    <!--xml  数据绑定 结束--> </Window>             //第二种读取方式   读取对象属性<Window.Resources>         <XmlDataProvider x:Key="xmlData" Source="pack://application:,,,/WpfApp2;component/simple.xml"> </XmlDataProvider>    </Window.Resources>            <Window>    <!--xml  数据绑定 开始-->    <TextBlock Text="{Binding Source={StaticResource xmlData},XPath= breakfast_menu/food[1]/name}"></TextBlock>    <!--xml  数据绑定 结束--> </Window>//备注：xml文件多节点下标是从1开始的。

5）ObjectDataProvider作为数据源
新建类：【MethodClass】

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WpfApp2
{
    public  class MothedClass
    {
        public double GetValue(string value)
        {
            return double.Parse(value) * 0.5;
        }
    }
}

xmal 代码如下：

<Window x:Class="WpfApp2.MainWindow"
        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"
        xmlns:local="clr-namespace:WpfApp2"
        xmlns:sys="clr-namespace:System;assembly=System.Runtime"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <ObjectDataProvider ObjectType="{x:Type local:MothedClass}" x:Key="dataobject" MethodName="GetValue">
            <ObjectDataProvider.MethodParameters>
                <sys:String>
                    200
                </sys:String>
            </ObjectDataProvider.MethodParameters>
        </ObjectDataProvider>
    </Window.Resources>
    <Grid>
        <Border BorderBrush="Black" BorderThickness="1" Height="{Binding Source={StaticResource dataobject}}" Width="{Binding Source={StaticResource dataobject}}">
            <TextBlock Text="{Binding Source={StaticResource dataobject}}"></TextBlock>
        </Border>
    </Grid>
</Window>

6）静态对象属性作为数据源
新建静态类:[StaticClass]

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace WpfApp2
{
    public  class StaticClass
    {  
        public static int MyProperty { get; set; } = 555;
        //通知  第一种方式  [Value]Changed  必须与属性名称一一对应【不推荐】
        public static  event  EventHandler<PropertyChangedEventArgs> ValueChanged;
        //通知  第二种方式
        public static event EventHandler<PropertyChangedEventArgs> StaricPropertyChanged;

        private static int value { get; set; }=66;
        public static int Value
        {
            get { return value; }
            set { Value = value;
                //通知  第一种方式 【不推荐】
                // ValueChanged?.Invoke(null,new  PropertyChangedEventArgs("Value"));
                //通知  第二种方式
                StaricPropertyChanged?.Invoke(null, new PropertyChangedEventArgs("Value"));
            }
        }  
    }
}

xaml:代码如下

<Window x:Class="WpfApp2.MainWindow"
        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"
        xmlns:local="clr-namespace:WpfApp2"
        xmlns:sys="clr-namespace:System;assembly=System.Runtime"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800" Name="window"> 
    <Grid>
        <StackPanel> 
            <!--静态对象属性绑定--> 
            <!--单一绑定值-->
            <TextBlock Text="{Binding Path=(local:StaticClass.MyProperty)}"></TextBlock>
            <!--属性值发生变化后通知属性变化  第一种方式-->
            <TextBlock Text="{Binding Path=(local:StaticClass.Value)}"></TextBlock>
        </StackPanel>  
    </Grid>
</Window>

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