[置顶] 当前上下文不存在 ScriptManager 的原因分析以及解决方案 (System.Web.Extensions)

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;

        }


    }
}