Chapter 2. Data Binding (1)

We manually write code to ensure UI and data synchronization. The two groups of attributes are implicitly bound together. One group comes from the person object and the other is from the controls that display the person object. Data Binding is used to explicitly bind attributes from one object to another to keep them synchronized and convert them to an appropriate type, as shown in Figure 4-7.

Figure 4-7

{
Get_larger (this)
} "Src =" http://img.ddvip.com/2009_03_09/1236585568_ddvip_6082.gif "alt =" programming WPF Chapter 2. Data Binding "width =" 4th "Height =" 440 ">

4.2.1 binding

To manually set the text attributes of textbox objects in the Code and ensure they are up-to-date, Data Binding allows us to set the text attributes using the binding object instance, as shown in Figure 4-8.

Example 4-8

<TextBox >
　 <TextBox.Text>
　　　 <Binding Path="Age" />
　 </TextBox.Text>
</TextBox>

In Example 4-8, we have used the attribute element syntax introduced in chapter 1 to create an instance of the binding class and initialized its path attribute as "age ", set the binding object to the text attribute value of the textbox object. Use the bound tag (also introduced in chapter 1). For example 4-8, use 4-9.

Example 4-9

<TextBox TextContent="{Binding Path=Age}" />

As a shorter version, you can omit the specified path, and the binding can also know what it means, as shown in Example 4-10.

Example 4-10

<TextBox TextContent="{Binding Age}" />

I prefer to display the syntax Declaration, so I will not use the syntax for example 4-10, but I will not comment on it-if you like to use it

The binding class provides a variety of interesting tools to manage the binding between attributes, but we are more concerned with the path attribute. In most cases, you may consider path as the attribute name of an object and as the data source. Therefore, the binding statement in the example 4-10 creates a binding between the text attribute of a textbox and the name attribute of an object, as shown in Figure 4-8.

We manually write code to ensure UI and data synchronization. The two groups of attributes are implicitly bound together. One group comes from the person object and the other is from the controls that display the person object. Data Binding is used to explicitly bind attributes from one object to another to keep them synchronized and convert them to an appropriate type, as shown in Figure 4-7.

Figure 4-7

{
Get_larger (this)
} "Src =" http://img.ddvip.com/2009_03_09/1236585568_ddvip_6082.gif "alt =" programming WPF Chapter 2. Data Binding "width =" 4th "Height =" 440 ">

4.2.1 binding

To manually set the text attributes of textbox objects in the Code and ensure they are up-to-date, Data Binding allows us to set the text attributes using the binding object instance, as shown in Figure 4-8.

Example 4-8

<TextBox >
　 <TextBox.Text>
　　　 <Binding Path="Age" />
　 </TextBox.Text>
</TextBox>

In Example 4-8, we have used the attribute element syntax introduced in chapter 1 to create an instance of the binding class and initialized its path attribute as "age ", set the binding object to the text attribute value of the textbox object. Use the bound tag (also introduced in chapter 1). For example 4-8, use 4-9.

Example 4-9

<TextBox TextContent="{Binding Path=Age}" />

As a shorter version, you can omit the specified path, and the binding can also know what it means, as shown in Example 4-10.

Example 4-10

<TextBox TextContent="{Binding Age}" />

I prefer to display the syntax Declaration, so I will not use the syntax for example 4-10, but I will not comment on it-if you like to use it

The binding class provides a variety of interesting tools to manage the binding between attributes, but we are more concerned with the path attribute. In most cases, you may consider path as the attribute name of an object and as the data source. Therefore, the binding statement in the example 4-10 creates a binding between the text attribute of a textbox and the name attribute of an object, as shown in Figure 4-8.

The procedure is as follows:

L The binding mechanism searches for non-empty datacontext attributes in textbox itself

L The binding mechanism searches for non-empty datacontext attributes in the grid.

L The binding mechanism searches for non-empty datacontext attributes in the window

Provide a non-empty datacontext for both text box controls. In the window1 constructor, set the shared person object as the datacontext attribute of the grid, as shown in Example 4-11.

Example 4-11

// Window1.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;

namespace PersonBinding {
　 public partial class Window1 : Window {
　　　 Person person = new Person("Tom", 9);

　　　 public Window1(　 ) {
　　　　　 InitializeComponent(　 );

　　　　　 // Let the grid know its data context
　　　　　 grid.DataContext = person;

　　　　　 this.birthdayButton.Click += birthdayButton_Click;
　　　 }

　　　 void birthdayButton_Click(object sender, RoutedEventArgs e) {
　　　　　 // Data binding keeps person and the text boxes synchronized
　　　　　 ++person.Age;
　　　　　 MessageBox.Show(
　　　　　　　 string.Format(
　　　　　　　　　 "Happy Birthday, {0}, age {1}!",
　　　　　　　　　 person.Name,
　　　　　　　　　 person.Age),
　　　　　　　 "Birthday");
　　　 }
　 }
}