错误如下图：
当我们在写web程序的时候，有时候避免不了要再后台弹出一个提示框，在winform中我们可以用MssageBox() 类来实现，在web开发中，我们只能借助于javascript来实现了
.net中为我们提供了这样一个类ScriptManager来帮助我们解决这样的问题，而有些时候我们却在使用的时候容易出现这样一个错误，”当前上下文不存在 ScriptManager ” ，这就很郁闷了，差资料显示 ScriptManager 类存在于 System.Web.UI 命名空间中，这时我们在类的头部添加引用，using System.Web.UI;或者是继承 System.Web.UI.Page 这样还是不行，郁闷了，查资料，显示 System.Web.UI类存在于 程序集： System.Web.Extensions（在 System.Web.Extensions.dll 中），这时，有人会在类头部这样写，Using System.Web.Extensions; 这样是不行的，我们必须在项目中，添加引用，
示例如下图：
第二步：
“
msdn论坛：http://msdn.microsoft.com/zh-cn/library/system.web.ui.scriptmanager%28v=vs.100%29.aspx点击打开链接
示例类如下：类PageUtil
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
namespace shouqiang_Wei
{
public class PageUtil:System.Web.UI.Page
{
#region 截取字符长度
/// <summary>
/// 截取字符长度
/// </summary>
/// <param name="inputString">字符</param>
/// <param name="len">长度</param>
/// <returns></returns>
public static string CutString(string inputString, int len)
{
if (string.IsNullOrEmpty(inputString))
return "";
inputString = DropHTML(inputString);
ASCIIEncoding ascii = new ASCIIEncoding();
int tempLen = 0;
string tempString = "";
byte[] s = ascii.GetBytes(inputString);
for (int i = 0; i < s.Length; i++)
{
if ((int)s[i] == 63)
{
tempLen += 2;
}
else
{
tempLen += 1;
}
try
{
tempString += inputString.Substring(i, 1);
}
catch
{
break;
}
if (tempLen > len)
break;
}
//如果截过则加上半个省略号
byte[] mybyte = System.Text.Encoding.Default.GetBytes(inputString);
if (mybyte.Length > len)
tempString += "…";
return tempString;
}
#endregion
#region 清除HTML标记
public static string DropHTML(string Htmlstring)
{
if (string.IsNullOrEmpty(Htmlstring)) return "";
//删除脚本
Htmlstring = Regex.Replace(Htmlstring, @"<script[^>]*?>.*?</script>", "", RegexOptions.IgnoreCase);
//删除HTML
Htmlstring = Regex.Replace(Htmlstring, @"<(.[^>]*)>", "", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"([\r\n])[\s]+", "", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"-->", "", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"<!--.*", "", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(quot|#34);", "\"", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(amp|#38);", "&", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(lt|#60);", "<", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(gt|#62);", ">", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(nbsp|#160);", " ", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(iexcl|#161);", "\xa1", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(cent|#162);", "\xa2", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(pound|#163);", "\xa3", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&(copy|#169);", "\xa9", RegexOptions.IgnoreCase);
Htmlstring = Regex.Replace(Htmlstring, @"&#(\d+);", "", RegexOptions.IgnoreCase);
Htmlstring.Replace("<", "");
Htmlstring.Replace(">", "");
Htmlstring.Replace("\r\n", "");
Htmlstring = HttpContext.Current.Server.HtmlEncode(Htmlstring).Trim();
return Htmlstring;
}
#endregion
/// <summary>
/// 在web页面上显示一个对话框
/// </summary>
/// <param name="page"></param>
/// <param name="msg"></param>
public static void ShowMsgBox(System.Web.UI.Control page, string msg)
{
string m = HttpUtility.HtmlEncode(msg);
ExecJavaScript(page, "alert('" + m + "');");
}
public static void ShowCfmMsgBox(System.Web.UI.Control page, string msg)
{
string m = HttpUtility.HtmlEncode(msg);
ExecJavaScript(page, "confirm('" + m + "');");
}
/// <summary>
/// 显示提示信息并转向新的页面
/// </summary>
/// <param name="page"></param>
/// <param name="msg"></param>
/// <param name="newurl"></param>
public static void ShowMsgBoxAndRedirect(System.Web.UI.Control page, string msg, string newurl)
{
string m = HttpUtility.HtmlEncode(msg);
ExecJavaScript(page, "alert('" + m + "'); window.location='" + newurl + "';");
}
/// <summary>
/// Add by shouqiang Wei 改成 confirm 这样的话就可以返回了...> 不知道能不能行？
/// </summary>
/// <param name="page"></param>
/// <param name="msg"></param>
/// <param name="newurl"></param>
public static void ShowCfmMsgBoxAndRedirect(System.Web.UI.Control page, string msg, string newurl)
{
string m = HttpUtility.HtmlEncode(msg);
ExecJavaScript(page, "if(confirm('" + m + "')) window.location='" + newurl + "' ;");
}
/// <summary>
/// 子框架中转向
/// </summary>
/// <param name="page"></param>
/// <param name="newurl"></param>
public static void ParentPageRedirect(System.Web.UI.Control page, string newurl)
{
ExecJavaScript(page, " self.parent.window.location='" + newurl + "';");
}
/// <summary>
/// 在web页面上添加一段javascript
/// </summary>
/// <param name="page"></param>
/// <param name="script"></param>
public static void ExecJavaScript(System.Web.UI.Control page, string script)
{
ScriptManager.RegisterStartupScript(page, page.GetType(), "a", script, true);
}
/// <summary>
/// MD5摘要
/// </summary>
/// <param name="cleanString"></param>
/// <returns></returns>
public static string Md5Encrypt(string cleanString)
{
Byte[] clearBytes = new UnicodeEncoding().GetBytes(cleanString);
Byte[] hashedBytes = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(clearBytes);
return BitConverter.ToString(hashedBytes);
}
/// <summary>
/// SQL防注入攻击，数据过滤
/// </summary>
/// <param name="value">要过滤的数据</param>
/// <returns>过滤后的数据</returns>
public static string SQLFilter(string value)
{
if (String.IsNullOrEmpty(value)) return "";
value = value.Trim();
value = HttpUtility.HtmlEncode(value);
value = value.Replace(" and ", "***");
value = value.Replace(" or ", "***");
value = value.Replace(" truncate ", "***");
value = value.Replace(" from ", "***");
value = value.Replace(" select ", "***");
value = value.Replace(" insert ", "***");
value = value.Replace(" update ", "***");
value = value.Replace(" delete ", "***");
value = value.Replace(" drop ", "***");
value = value.Replace(" count ", "***");
value = value.Replace(" exec ", "***");
return value;
}
public static string GetSex(object obj)
{
if (obj == null)
{
return "未知";
}
try
{
bool sex = bool.Parse(obj.ToString());
if (sex)
{
return "男";
}
else
return "女";
}
catch (Exception ex)
{
return "未知";
}
}
public static string GetClosedStatus(object obj)
{
if (obj == null)
{
return "未知";
}
else
{
try
{
int n = int.Parse(obj.ToString());
if (n == 1)
{
return "关闭";
}
else if (n == 0)
return "开放";
else
return "未知";
}
catch (Exception ex)
{
return "未知";
}
}
}
public static string SubString(object obj, int length)
{
if (obj == null)
return "";
string str = obj.ToString();
if (str.Length > length)
return str.Substring(0, length);
return str;
}
}
}