WPF binding expression and binding data source (I)

About binding ：[Binding]

binding ： It describes a relationship , Isomorphism is a relationship that connects multiple things .

• ​ Properties of page objects （ Must be a dependent property ）： The goal is Target

• ​ Data objects that need to be displayed on the interface for interactive association ： Source 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>
    // remarks ：
    //Text： The goal is 
    //Source=data,Path=value    Source ：   It's also a binding expression 
              
  

1、 Binding expression

Text="{Binding Source=data,Path=value}" : Connect a property of the page object with the data source .

​ The interface can be isolated from the data logic through binding .

2、 Bind data source

1、 Specify the way ：

​ Source、ElementName、DataContext、RelativeSource、Path、XPath

​ 2、 Data source type

​ 1） Dependent objects as data sources

<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>
          <!-- Dependent object binding -->
        <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 Current value ："></TextBlock>
            <TextBlock  Text="{Binding  ElementName=slider,Path= Value}"></TextBlock>
            <Slider Width="200" Name="slider"  Minimum="5" Maximum="100" HorizontalAlignment="Left"></Slider>
            <TextBlock Text="Solider minimum value ："></TextBlock>
            <TextBlock Text="{Binding ElementName=slider,Path=Minimum}"></TextBlock>
        </StackPanel> 
    </Grid>
</Window>

​ 2） Common data type or collection type as data source

<Window.Resources>
        <sys:String x:Key="name"> Xiao Ming </sys:String>
        <x:Array x:Key="data" Type="sys:String">
            <sys:String> Xiaogang </sys:String>
        </x:Array>
    </Window.Resources>
    
     <!-- Common object , Collection object binding     Start -->
            <TextBlock Text="{Binding Source={StaticResource name}}"></TextBlock>
            <TextBlock Text="{Binding Source={StaticResource data},Path=[0]}"></TextBlock>
            <!-- Common object , Collection object binding     end -->

​ 3） Single object as data source ,INotifyPropertyChanged

The new class ：DataClass Inherit 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 Code ：

<Window.Resources> 
        <local:DataClass Value=" This is a single object as a data source ,INotifyPropertyChanged  " x:Key="dataclass"></local:DataClass>
    </Window.Resources> 
<Window>
<!-- Single object as data source ,INotifyPropertyChanged   Start -->
<TextBlock Text="{Binding Source={StaticResource dataclass},Path=Value}"></TextBlock>
<!-- Single object as data source ,INotifyPropertyChanged   end -->      
</Window>

xaml.cs Code ：

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 As a data source

Create a new one XML file ：【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 The code is as follows ：

//d The first way to read     Read object properties <Window.Resources>         <XmlDataProvider x:Key="xmlData" Source="pack://application:,,,/WpfApp2;component/simple.xml" XPath="breakfast_menu/food[1]"> </XmlDataProvider>    </Window.Resources>            <Window>    <!--xml   Data binding   Start -->    <TextBlock Text="{Binding Source={StaticResource xmlData},XPath= name}"></TextBlock>    <!--xml   Data binding   end --> </Window>             // The second way to read     Read object properties <Window.Resources>         <XmlDataProvider x:Key="xmlData" Source="pack://application:,,,/WpfApp2;component/simple.xml"> </XmlDataProvider>    </Window.Resources>            <Window>    <!--xml   Data binding   Start -->    <TextBlock Text="{Binding Source={StaticResource xmlData},XPath= breakfast_menu/food[1]/name}"></TextBlock>    <!--xml   Data binding   end --> </Window>// remarks ：xml The multi node subscript of the file is from 1 At the beginning .  

​

​ 5）ObjectDataProvider As a data source

​ The new class ：【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 The code is as follows ：

<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） Static object properties as data sources

​ New static class :[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;
        // notice    The first way   [Value]Changed   Must correspond to the attribute name one by one 【 Not recommended 】
        public static  event  EventHandler<PropertyChangedEventArgs> ValueChanged;
        // notice    The second way 
        public static event EventHandler<PropertyChangedEventArgs> StaricPropertyChanged;

        private static int value { get; set; }=66;
        public static int Value
        {
            get { return value; }
            set { Value = value;
                // notice    The first way  【 Not recommended 】
                // ValueChanged?.Invoke(null,new  PropertyChangedEventArgs("Value"));
                // notice    The second way 
                StaricPropertyChanged?.Invoke(null, new PropertyChangedEventArgs("Value"));
            }
        }  
    }
}

xaml: The code is as follows

<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> 
            <!-- Static object property binding --> 
            <!-- Single binding value -->
            <TextBlock Text="{Binding Path=(local:StaticClass.MyProperty)}"></TextBlock>
            <!-- Notify the attribute change when the attribute value changes -->
            <TextBlock Text="{Binding Path=(local:StaticClass.Value)}"></TextBlock>
        </StackPanel>  
    </Grid>
</Window>