写在前面：
此文用于收藏常用的方法。希望大家多多交流。
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1.截取指定长度的字符串并在末尾加入指定字符
01 /*
02 *方法说明：截取指定长度的字符串并在末尾加入指定字符
03 *参数说明：oldStr为原字符串，maxLength为截取长度，endWith为在末尾加入的字符
04 */
05 public static string StringTruncat(string oldStr, int maxLength, string endWith)
06 {
07 if (string.IsNullOrEmpty(oldStr))//原字符串为空时仅返回endWith
08 {
09 return oldStr + endWith;
10 }
11 if (maxLength<1)//指定长度必须大于0
12 {
13 throw new Exception("返回的字符串长度必须大于0");
14 }
15 if (oldStr.Length>maxLength)//原字符串长度大于截取长度时进行处理
16 {
17 string strTmp = oldStr.Substring(0, maxLength);//对原字符串的子串进行处理
18 if (string.IsNullOrEmpty(endWith))//如果endWith为空返回子串
19 {
20 return strTmp;
21 }
22 else
23 return strTmp + endWith;//给子串加的末尾加上指定字符
24 }
25 return oldStr;//原字符串长度小于等于截取长度时不作处理
2.验证码生成方法
首先在html页面中加入javascript，此处注意imgNode.src必须根据情况自行修改。然后，新建一个“一般处理程序”，将WaterMark类的所有代码全部复制进去即可。
01 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
02 <html>
03 <head>
04 <title></title>
05 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
06 <script type="text/">
07 function change() {
08 var imgNode = document.getElementById("vimg");
09 imgNode.src = "WaterMark.ashx?t=" + (new Date()).valueOf(); // 这里加个时间的参数是为了防止浏览器缓存的问题
10 }
11 </script>
12 </head>
13 <body>
14 <img src="WaterMark.ashx" id="vimg" alt="" onclick="change();"/>
15 </body>
16 </html>
01 <%@ WebHandler Language="C#" Class="WaterMark" %>
02
03 using System;
04 using System.Web;
05 using System.Drawing;
06 using System.Drawing.Drawing2D;
07 using System.Web.SessionState;
08
09 public class WaterMark : IHttpHandler, IRequiresSessionState // 要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间
10 {
11
12 public void ProcessRequest(HttpContext context)
13 {
14 string checkCode = GenCode(5); // 产生5位随机字符
15 context.Session["Code"] = checkCode; //将字符串保存到Session中，以便需要时进行验证
16 System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 22);
17 Graphics g = Graphics.FromImage(image);
18 try
19 {
20 //生成随机生成器
21 Random random = new Random();
22
23 //清空图片背景色
24 g.Clear(Color.White);
25
26 // 画图片的背景噪音线
27 int i;
28 for (i = 0; i < 25; i++)
29 {
30 int x1 = random.Next(image.Width);
31 int x2 = random.Next(image.Width);
32 int y1 = random.Next(image.Height);
33 int y2 = random.Next(image.Height);
34 g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
35 }
36
37 Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
38 System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true);
39 g.DrawString(checkCode, font, brush, 2, 2);
40
41 //画图片的前景噪音点
42 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
43 System.IO.MemoryStream ms = new System.IO.MemoryStream();
44 image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
45 context.Response.ClearContent();
46 context.Response.ContentType = "image/Gif";
47 context.Response.BinaryWrite(ms.ToArray());
48 }
49 finally
50 {
51 g.Dispose();
52 image.Dispose();
53 }
54 }
55
56 /// <summary>
57 /// 产生随机字符串
58 /// </summary>
59 /// <param name="num">随机出几个字符</param>
60 /// <returns>随机出的字符串</returns>
61 private string GenCode(int num)
62 {
63 string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
64 char[] chastr = str.ToCharArray();
65 // string[] source ={ "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "#", "$", "%", "&", "@" };
66 string code = "";
67 Random rd = new Random();
68 int i;
69 for (i = 0; i < num; i++)
70 {
71 //code += source[rd.Next(0, source.Length)];
72 code += str.Substring(rd.Next(0, str.Length), 1);
73 }
74 return code;
75
76 }
77
78 public bool IsReusable
79 {
80 get
81 {
82 return false;
83 }
84 }
85
86 }
3.无刷新实现弹窗
1 Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('加入暂存架成功！');</script>");
4.MD5转码
1 using System.Web.Security;//导入命名空间
2
3 string Password = FormsAuthentication.HashPasswordForStoringInConfigFile(TextBox1.Text.ToString(), "MD5");//进行转码
