INotifyPropertyChanged的作用
最近学习数据驱动UI，了解到INotifyPropertyChanged这个接口的用法，看了很多网上的文章，自己作了一个总结。
INotifyPropertyChanged这个接口其实非常简单，只有一个PropertyChanged事件，如果类继承了这个接口，就必须实现接口。用VS的提示，就是补充了一句话：
public event PropertyChangedEventHandler PropertyChanged;
using System; using System.Collections.Generic; using System.ComponentModel; using System.Linq; using System.Text; namespace Demo001 { class Student:INotifyPropertyChanged { private string name; private int age; public string Name { get { return name; } set { if (this.name == value) { return; } this.name = value; Notify("Name"); } } public int Age { get { return age; } set { if (this.age == value) { return; } this.age = value; Notify("Age"); } } public event PropertyChangedEventHandler PropertyChanged; protected void Notify(string propertyName) { if (this.PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } } }
剩下的就是对事件PropertyChanged的操作，于是我想可不可以直接定义这个事件而不继承接口INotifyPropertyChanged，结果发现也是可以的。
using System; using System.Collections.Generic; using System.ComponentModel; using System.Linq; using System.Text; namespace Demo001 { class Student { private string name; private int age; public string Name { get { return name; } set { if (this.name == value) { return; } this.name = value; Notify("Name"); } } public int Age { get { return age; } set { if (this.age == value) { return; } this.age = value; Notify("Age"); } } public event PropertyChangedEventHandler PropertyChanged; protected void Notify(string propertyName) { if (this.PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } } }
只不过这时候的PropertyChanged是自定义的事件了，我们可以随意改变这个名字，比如pChanged,但是继承INotifyPropertyChanged接口后，只能用PropertyChanged这个名字。
在Form中注册事件，附代码：
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace Demo001 { public partial class Form1 : Form { Student stu = new Student(); public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { stu.PropertyChanged += changed; } private void button1_Click(object sender, EventArgs e) { stu.Name = textBox1.Text; stu.Age = int.Parse(textBox2.Text); } public void changed(object sender, PropertyChangedEventArgs e) { switch(e.PropertyName) { case "Name": Console.WriteLine("Name Changed"); break; case "Age": Console.WriteLine("Age Changed"); break; } } } }
namespace Demo001 { partial class Form1 { /// <summary> /// 必需的设计器变量。 /// </summary> private System.ComponentModel.IContainer components = null; /// <summary> /// 清理所有正在使用的资源。 /// </summary> /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param> protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } #region Windows 窗体设计器生成的代码 /// <summary> /// 设计器支持所需的方法 - 不要修改 /// 使用代码编辑器修改此方法的内容。 /// </summary> private void InitializeComponent() { this.textBox1 = new System.Windows.Forms.TextBox(); this.label1 = new System.Windows.Forms.Label(); this.label2 = new System.Windows.Forms.Label(); this.textBox2 = new System.Windows.Forms.TextBox(); this.button1 = new System.Windows.Forms.Button(); this.SuspendLayout(); // // textBox1 // this.textBox1.Location = new System.Drawing.Point(59, 33); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(100, 21); this.textBox1.TabIndex = 0; // // label1 // this.label1.AutoSize = true; this.label1.Location = new System.Drawing.Point(12, 38); this.label1.Name = "label1"; this.label1.Size = new System.Drawing.Size(29, 12); this.label1.TabIndex = 1; this.label1.Text = "姓名"; // // label2 // this.label2.AutoSize = true; this.label2.Location = new System.Drawing.Point(12, 80); this.label2.Name = "label2"; this.label2.Size = new System.Drawing.Size(29, 12); this.label2.TabIndex = 3; this.label2.Text = "年龄"; // // textBox2 // this.textBox2.Location = new System.Drawing.Point(59, 75); this.textBox2.Name = "textBox2"; this.textBox2.Size = new System.Drawing.Size(100, 21); this.textBox2.TabIndex = 2; // // button1 // this.button1.Location = new System.Drawing.Point(59, 129); this.button1.Name = "button1"; this.button1.Size = new System.Drawing.Size(75, 23); this.button1.TabIndex = 4; this.button1.Text = "设定"; this.button1.UseVisualStyleBackColor = true; this.button1.Click += new System.EventHandler(this.button1_Click); // // Form1 // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.ClientSize = new System.Drawing.Size(195, 182); this.Controls.Add(this.button1); this.Controls.Add(this.label2); this.Controls.Add(this.textBox2); this.Controls.Add(this.label1); this.Controls.Add(this.textBox1); this.Name = "Form1"; this.Text = "Form1"; this.Load += new System.EventHandler(this.Form1_Load); this.ResumeLayout(false); this.PerformLayout(); } #endregion private System.Windows.Forms.TextBox textBox1; private System.Windows.Forms.Label label1; private System.Windows.Forms.Label label2; private System.Windows.Forms.TextBox textBox2; private System.Windows.Forms.Button button1; } }
备忘：委托是特殊的类，事件是一种委托，所以事件注册，应该是“附加”方法，而不是“等于”方法。
委托将参数传给相应的方法，一个作用是（子窗体）传递参数，另一个作用是（主窗体）调用方法。
委托传递参数，可以用于窗体传值，主窗口利用子窗体构造函数传值给子窗体，子窗体将值传给委托（=子窗体传值给主窗体的方法，从而传值给主窗体）。
委托调用方法，主窗体注册方法，子窗体定义委托（事件），在子窗体给委托传值的时候触发主窗体调用方法，从而改变主窗体的一些UI变化。
