不使用OnPaint()进行绘制

一些人在论坛上询问关于不使用OnPaint方法或事件进行绘画的问题。

为什么要使用onpaint函数呢？主要原因是我们可以轻易地使用paint函数得到Graphics对象。实际上，不使用onpaint函数进行绘制是非常简单的。只需要在正在绘制的窗体中得到Graphics对象即可。

 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel;
 4 using System.Data;
 5 using System.Drawing;
 6 using System.Linq;
 7 using System.Text;
 8 using System.Windows.Forms;
 9 
10 namespace DrawWithNoPaintDemo
11 {
12     public partial class Form1 : Form
13     {
14         public Form1()
15         {
16             InitializeComponent();
17         }
18 
19         private void radioButton1_CheckedChanged(object sender, EventArgs e)
20         {
21 
22         }
23 
24         private void button1_Click(object sender, EventArgs e)
25         {
26             Graphics grfx = Graphics.FromHwnd(this.Handle);
27             //Graphics grfx = CreateGraphics();
28             Pen pn = new Pen(Color.Blue,10);
29             SolidBrush br = new SolidBrush(Color.AliceBlue);
30             Rectangle rc = new Rectangle(200,50,200,200);
31 
32             if (radioButton1.Checked)
33             {
34                 pn.Color = Color.Red;
35                 br.Color = Color.Red;
36             }
37             if (radioButton2.Checked)
38             {
39                 pn.Color = Color.Green;
40                 br.Color = Color.Green;
41             }
42             if (radioButton3.Checked)
43             {
44                 pn.Color = Color.Blue;
45                 br.Color = Color.Blue;
46             }
47 
48             if (checkBox1.Checked)
49             {
50                 grfx.FillEllipse(br,rc);
51                 grfx.DrawEllipse(pn,rc);
52             }
53             if (checkBox2.Checked)
54             {
55                 grfx.DrawRectangle(pn,rc);
56             }
57             if (checkBox3.Checked)
58             {
59                 grfx.DrawString("Test String",new Font("Verdana",14),new SolidBrush(Color.Black),rc);
60             }
61 
62             pn.Dispose();
63             br.Dispose();
64         }
65     }
66 }