先放入正常的代码，如下：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Drawing;
6 using System.Windows.Forms;
7
8 namespace RadioButtons
9 {
10 class RadioButtons:Form
11 {
12 bool bFillEllipse;
13 Color colorEllipse;
14 int n = 0;
15
16 static void Main(string[] args)
17 {
18 Application.Run(new RadioButtons());
19 }
20 public RadioButtons()
21 {
22 Text = "Radio Buttons Demo";
23 ResizeRedraw = true;
24
25 string[] astrColor = { "Black","Blue","Green","Cyan",
26 "Red","Magenta","Yellow","White"};
27 GroupBox grpbox = new GroupBox();
28 grpbox.Parent = this;
29 grpbox.Text = "Color";
30 grpbox.Location = new Point(Font.Height,Font.Height);
31 grpbox.Size = new Size(9 * Font.Height,
32 (3 * astrColor.Length + 4) * Font.Height/2);
33 for (int i = 0; i < astrColor.Length; i++)
34 {
35 RadioButton radiobtn = new RadioButton();
36 radiobtn.Parent = grpbox;
37 radiobtn.Text = astrColor[i];
38 radiobtn.Location = new Point(Font.Height,
39 3 * (i + 1) * Font.Height/2);
40 radiobtn.Size = new Size(7 * Font.Height,
41 3 * Font.Height/2);
42 //单选按钮事件
43 radiobtn.CheckedChanged += new EventHandler(radiobtn_CheckedChanged);
44
45 if (i == 0)
46 {
47 radiobtn.Checked = true;
48 }
49 }
50 CheckBox chkbox = new CheckBox();
51 chkbox.Parent = this;
52 chkbox.Text = "Fill Ellipse";
53 chkbox.Location = new Point(Font.Height,
54 3 * (astrColor.Length + 2) * Font.Height/2);
55 chkbox.Size = new Size(Font.Height * 7,3 * Font.Height/2);
56 chkbox.CheckedChanged += new EventHandler(chkbox_CheckedChanged);
57 }
58
59 void chkbox_CheckedChanged(object sender, EventArgs e)
60 {
61 bFillEllipse = ((CheckBox)sender).Checked;
62 Invalidate(false);
63
64 }
65 //单选按钮事件的具体实现
66 void radiobtn_CheckedChanged(object sender, EventArgs e)
67 {
68 RadioButton radiobtn = (RadioButton)sender;
69 if (radiobtn.Checked)
70 {
71 colorEllipse = Color.FromName(radiobtn.Text);
72 Invalidate(false);
73
74 }
75 }
76 protected override void OnPaint(PaintEventArgs e)
77 {
78 Graphics grfx = CreateGraphics();
79
80 //测试
81 grfx.DrawString("这是第一行",Font,new SolidBrush(Color.Red),0,n * Font.Height);
82 n++;
83 Console.WriteLine(n);
84
85 Rectangle rect = new Rectangle(10 * Font.Height,0,
86 ClientSize.Width-10*Font.Height-1,
87 ClientSize.Height-1);
88 if (bFillEllipse)
89 {
90 grfx.FillEllipse(new SolidBrush(colorEllipse), rect);
91 }
92 else
93 grfx.DrawEllipse(new Pen(colorEllipse),rect);
94 }
95 }
96 }
按住界面右下角，间断拖动，可以看到红色字体“这是第一行”和右侧的“椭圆”是随着每次的拖动在不停变化的；
下面尝试将//ResizeRedraw = true;注释掉，看看会发生什么情况 ？代码如下：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Drawing;
6 using System.Windows.Forms;
7
8 namespace RadioButtons
9 {
10 class RadioButtons:Form
11 {
12 bool bFillEllipse;
13 Color colorEllipse;
14 int n = 0;
15
16 static void Main(string[] args)
17 {
18 Application.Run(new RadioButtons());
19 }
20 public RadioButtons()
21 {
22 Text = "Radio Buttons Demo";
23 //ResizeRedraw = true;
24
25 string[] astrColor = { "Black","Blue","Green","Cyan",
26 "Red","Magenta","Yellow","White"};
27 GroupBox grpbox = new GroupBox();
28 grpbox.Parent = this;
29 grpbox.Text = "Color";
30 grpbox.Location = new Point(Font.Height,Font.Height);
31 grpbox.Size = new Size(9 * Font.Height,
32 (3 * astrColor.Length + 4) * Font.Height/2);
33 for (int i = 0; i < astrColor.Length; i++)
34 {
35 RadioButton radiobtn = new RadioButton();
36 radiobtn.Parent = grpbox;
37 radiobtn.Text = astrColor[i];
38 radiobtn.Location = new Point(Font.Height,
39 3 * (i + 1) * Font.Height/2);
40 radiobtn.Size = new Size(7 * Font.Height,
41 3 * Font.Height/2);
42 //单选按钮事件
43 radiobtn.CheckedChanged += new EventHandler(radiobtn_CheckedChanged);
44
45 if (i == 0)
46 {
47 radiobtn.Checked = true;
48 }
49 }
50 CheckBox chkbox = new CheckBox();
51 chkbox.Parent = this;
52 chkbox.Text = "Fill Ellipse";
53 chkbox.Location = new Point(Font.Height,
54 3 * (astrColor.Length + 2) * Font.Height/2);
55 chkbox.Size = new Size(Font.Height * 7,3 * Font.Height/2);
56 chkbox.CheckedChanged += new EventHandler(chkbox_CheckedChanged);
57 }
58
59 void chkbox_CheckedChanged(object sender, EventArgs e)
60 {
61 bFillEllipse = ((CheckBox)sender).Checked;
62 Invalidate(false);
63
64 }
65 //单选按钮事件的具体实现
66 void radiobtn_CheckedChanged(object sender, EventArgs e)
67 {
68 RadioButton radiobtn = (RadioButton)sender;
69 if (radiobtn.Checked)
70 {
71 colorEllipse = Color.FromName(radiobtn.Text);
72 Invalidate(false);
73
74 }
75 }
76 protected override void OnPaint(PaintEventArgs e)
77 {
78 Graphics grfx = CreateGraphics();
79
80 //测试
81 grfx.DrawString("这是第一行",Font,new SolidBrush(Color.Red),0,n * Font.Height);
82 n++;
83 Console.WriteLine(n);
84
85 Rectangle rect = new Rectangle(10 * Font.Height,0,
86 ClientSize.Width-10*Font.Height-1,
87 ClientSize.Height-1);
88 if (bFillEllipse)
89 {
90 grfx.FillEllipse(new SolidBrush(colorEllipse), rect);
91 }
92 else
93 grfx.DrawEllipse(new Pen(colorEllipse),rect);
94 }
95 }
96 }
拖动界面右下角，不断放大，可以看到，“文字”和“椭圆”没有自动刷新，产生了多次重叠。
由此可见，ResizeRedraw = true;的作用就很明显了！
标签：体会,using,Height,radiobtn,new,ResizeRedraw,Font,true,chkbox From： https://www.cnblogs.com/chenlight/p/16795689.html