请大虾相助，关于多人访问网页出错的问题

Question

本人新手，因为需要做了个站点，在制作的时候访问没问题，但是让学生参与的时候，五十几个人，就要出错，请大虾指点，谢谢！网页界面
多人访问时的出错页面
网页界面的那个页面的代码
<%@ Page Language="C#"  MasterPageFile="MasterPage3.master" AutoEventWireup="true" CodeFile="SZDknowledge.aspx.cs" Inherits="student_knowledge" %><%@ Register assembly="AspNetPager" namespace="Wuqi.Webdiyer" tagprefix="webdiyer" %><asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<script src="/images/dhtmlwindow.js" type="text/javascript"></script> 
   <script type="text/javascript">
     function opwins(url){
    var win=dhtmlwindow.open("dealbox", "iframe", url, "提示：鼠标点此移动窗口，拖动窗口右下角改变窗口大小", "width=640px,height=480px,left=100px,top=50px,resize=1,scrolling=0","recal");
    }
   </script> 
<link href="/images/dhtmlwindow.css" rel="Stylesheet" type="text/css" />
    <div>
    
        <table align="center" width="100%">
            <tr>
                <td width="180px" valign="top">
<asp:TreeView ID="TreeView1" runat="server" EnableViewState="False" ShowLines="True">
                 </asp:TreeView>
                </td>
                 <td valign="top">
                
                    <asp:Image ID="Image1" runat="server" ImageUrl="~/images/line.gif" />
                
                </td>
                <td valign="top">
                    <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
                        ConnectionString="<%$ ConnectionStrings:xxzdConnectionString %>" 
                        SelectCommand="SELECT [ClassName], [ClassID] FROM [ZDClass] where Tdepth=4">
                        
                    </asp:SqlDataSource>
                    
                    <br />
                    
                    <asp:DataList Id="dlCategories" runat="server" >
                        <ItemTemplate>
                           <%# DataBinder.Eval(Container, "DataItem.ClassName") %>
                            <br />
                            
                           <%# ShowResource(Convert.ToString(DataBinder.Eval(Container.DataItem, "ClassID")))%>
                                   
                            <br />
                            <br />
                        </ItemTemplate>
                    </asp:DataList>
                        
                    <br />
                    <table style="width: 98%; background-color: #D2E9FF;" cellpadding="0" 
                        cellspacing="0"> 
                    <tr> 
                    <td style="width:976px; height:25px;"> 
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
                    <asp:Label ID="Label7" runat="server" Text="当前页码"></asp:Label>                     
                    <asp:Label ID="labPage" runat="server" Text="1"></asp:Label>                    
                    <asp:Label ID="Label6" runat="server" Text="/"></asp:Label>                     
                    <asp:Label ID="labBackPage" runat="server"></asp:Label> 
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
                    <asp:LinkButton ID="lnkbtnOne" runat="server" Font-Underline="False" ForeColor="Red" 
                    OnClick="lnkbtnOne_Click">首页</asp:LinkButton> 
                    <asp:LinkButton ID="lnkbtnUp" runat="server" Font-Underline="False" ForeColor="Red" 
                    OnClick="lnkbtnUp_Click">上一页</asp:LinkButton> 
                    <asp:LinkButton ID="lnkbtnNext" runat="server" Font-Underline="False" ForeColor="Red" 
                    OnClick="lnkbtnNext_Click">下一页</asp:LinkButton> 
                    <asp:LinkButton ID="lnkbtnBack" runat="server" Font-Underline="False" ForeColor="Red" 
                    OnClick="lnkbtnBack_Click">尾页</asp:LinkButton> 
                        <asp:HiddenField ID="HiddenField1" runat="server" />
                        </td> 
                    </tr> 
                    </table> 
                        
                    </td>
            </tr>
        </table>
    
    </div>
</asp:Content>

Answer 1

相关cs代码
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
public partial class student_knowledge : System.Web.UI.Page
{    protected void Page_Load(object sender, EventArgs e)
    {
        InitTree();
                if (!IsPostBack)
        {
            DataAccess.IsAdmin(3);
                                   //传递参数后 根据参数返回相应数据
            if (Request["classID"] != null)
            {
                try
                {
                    int ClassID = Convert.ToInt32(Request.QueryString["classID"]);
                    if (ClassID == 0)
                    {
                        SqlDataSource1.SelectCommand = "SELECT * FROM ZDClass where Tdepth=4 order by classid";
                                               
                    }
                    else
                    {
                        string childclassid = getchild(ClassID);
                        SqlDataSource1.SelectCommand = "SELECT * FROM ZDClass where Tdepth=4 and ClassID in (" + childclassid + ") ";
                       
                    }                    HiddenField1.Value = SqlDataSource1.SelectCommand;
                    dlBind(SqlDataSource1.SelectCommand);                     //SqlDataSource1.ConnectionString = ConfigurationManager.ConnectionStrings["xxzdConnectionString"].ConnectionString;
                    
                    
                }
                catch
                {
                    Response.Write("<script language=\"javascript\">alert('参数传递错误!');history.back();</script>");
                    Response.End();
                }
                finally
                {
                    // int ClassID = Convert.ToInt32(Request.QueryString["classID"]);
                    DataAccess.Close();
                    
                }
            }
        }    }    public void dlBind(string chasql) 
    {
    string strCon = ConfigurationManager.ConnectionStrings["xxzdConnectionString"].ConnectionString; 
    int curpage = Convert.ToInt32(this.labPage.Text); 
    PagedDataSource ps = new PagedDataSource(); 
    SqlConnection sqlcon = new SqlConnection(strCon); 
    sqlcon.Open();
    string sqlstr = "SELECT * FROM ZDClass where Tdepth=4 ";
    if (chasql != "")
    {
        sqlstr = chasql;
    }    SqlDataAdapter MyAdapter = new SqlDataAdapter(sqlstr,sqlcon);     DataSet ds = new DataSet(); 
    MyAdapter.Fill(ds, "classid"); 
    ps.DataSource = ds.Tables["classid"].DefaultView; 
    ps.AllowPaging = true; //是否可以分页 
    ps.PageSize = 10; //显示的数量 
    ps.CurrentPageIndex = curpage - 1; //取得当前页的页码 
    this.lnkbtnUp.Enabled = true; 
    this.lnkbtnNext.Enabled = true; 
    this.lnkbtnBack.Enabled = true; 
    this.lnkbtnOne.Enabled = true; 
    if (curpage == 1) 
    { 
    this.lnkbtnOne.Enabled = false;//不显示第一页按钮 
    this.lnkbtnUp.Enabled = false;//不显示上一页按钮 
    } 
    if (curpage == ps.PageCount) 
    { 
    this.lnkbtnNext.Enabled = false;//不显示下一页 
    this.lnkbtnBack.Enabled = false;//不显示最后一页 
    } 
    this.labBackPage.Text = Convert.ToString(ps.PageCount);
    this.dlCategories.DataSource = ps;
    this.dlCategories.DataKeyField = "classid";
    this.dlCategories.DataBind();
    sqlcon.Close();
    sqlcon.Dispose();
    }     protected void lnkbtnOne_Click(object sender, EventArgs e) 
    { 
    this.labPage.Text = "1"; 
    this.dlBind(HiddenField1.Value.ToString()); 
    } 
    protected void lnkbtnUp_Click(object sender, EventArgs e) 
    { 
    this.labPage.Text = Convert.ToString(Convert.ToInt32(this.labPage.Text) - 1);
    this.dlBind(HiddenField1.Value.ToString());  
    } 
    protected void lnkbtnNext_Click(object sender, EventArgs e) 
    { 
    this.labPage.Text = Convert.ToString(Convert.ToInt32(this.labPage.Text) + 1);
    this.dlBind(HiddenField1.Value.ToString()); 
    } 
    protected void lnkbtnBack_Click(object sender, EventArgs e) 
    { 
    this.labPage.Text = this.labBackPage.Text;
    this.dlBind(HiddenField1.Value.ToString()); 
    }
    private string getchild(int parid)
    {
        string getchildstr="0";
        int ttdepth;
        string sql = "select * from zdclass where ClassID="+parid.ToString();
        ttdepth = Convert.ToInt16(DataAccess.GetDataTable(sql).Rows[0]["Tdepth"]);
        if (ttdepth == 4)
        {
            getchildstr = getchildstr + "," + parid.ToString();
        }
        else
        {
            string Sql = "select * from zdclass where ParentID=" + parid.ToString();
            DataTable dt = DataAccess.GetDataTable(Sql);
            DataRow[] drs = dt.Select("ParentID=" + parid.ToString());
            foreach (DataRow dr in drs)
            {
                if (dr["Tdepth"].ToString() == "4")
                {
                    getchildstr = getchildstr + "," + dr["ClassID"].ToString();
                }
                else
                {
                    getchildstr = getchildstr + "," + getchild(Convert.ToInt16(dr["ClassID"]));
                }
            }
        }
        return getchildstr;
    
    }    public string ShowResource(string classids) 
    {
        string showresourcestr = "";
        string Sql = "select * from ZDResource where Rnode=" + Convert.ToInt16(classids)+" and Rstat=0";
        DataTable dt = DataAccess.GetDataTable(Sql);
        DataRow[] drs = dt.Select("Rnode=" + Convert.ToInt16(classids));
        string picurl = "";
        foreach (DataRow dr in drs)
        {
            string rrtype = dr["Rtype"].ToString();
            switch (rrtype)
            {
                case "文本": picurl = "/images/wenben.png"; break;
                case "图片": picurl = "/images/tupian.png"; break;
                case "视频": picurl = "/images/shipin.png"; break;
                case "FLASH":picurl = "/images/flash.png"; break;
                case "实验": picurl = "/images/default.png"; break;
                default: picurl = ""; break;
            }
            string urlget = "SZDshowresource.aspx?rid=" + dr["Rid"];
            showresourcestr = showresourcestr + "<a href='#' onclick=javascript:opwins('" + urlget + "'); return false;><img src='" + picurl + "'></a>";
        }
        return showresourcestr;
    
    }
        private void InitTree()
    {
        TreeView1.Nodes.Clear();
        TreeNode rootNode = new TreeNode();
        rootNode.Text = "知识结构";
        rootNode.Value = "0";
        rootNode.NavigateUrl = "?classID=0";
        TreeView1.Nodes.Add(rootNode);
        //string Sql = "select * from zdclass where Tdepth<4 order by SortNumber asc";
        DataTable dt = DataAccess.getinittreetable();
        AddNote(dt, rootNode, 0);
        TreeView1.ExpandAll();
    }
    //子节点生成
    private void AddNote(DataTable dt, TreeNode node, int fatherid)
    {
        DataRow[] drs = dt.Select("ParentID=" + fatherid.ToString());
        foreach (DataRow dr in drs)
        {
            TreeNode childNode = new TreeNode();
            string ChiText = "";            childNode.Text = dr["className"].ToString() + ChiText.ToString();
            childNode.Value = dr["classid"].ToString();
            childNode.NavigateUrl = "?classID=" + dr["classid"].ToString();            node.ChildNodes.Add(childNode);            AddNote(dt, childNode, Convert.ToInt32(dr["classid"]));
        }
    }  
}

Answer 2

用到的数据库操作类
using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.SessionState;/// <summary>
/// 数据类
/// </summary>
public class DataAccess
{
    private static SqlConnection Conn = new SqlConnection();
    private static SqlCommand Cmd = new SqlCommand();
       public DataAccess()
    {    }    /// <summary>
    /// 打开连接
    /// </summary>    public static void Open()
    {
        if (Conn.State.Equals(ConnectionState.Closed))
        {
            Conn.ConnectionString = ConfigurationManager.ConnectionStrings["xxzdConnectionString"].ConnectionString;
            Cmd.Connection = Conn;
            Conn.Open();
        }
    }    /// <summary>
    /// 关闭连接
    /// </summary>
    public static void Close()
    {
        if (Conn.State == ConnectionState.Open)
        {
            Conn.Close();
            Conn.Dispose();
            Cmd.Dispose();
        }
    }    public static DataTable getcunchutable()
    {
        try
        {            Open();                     SqlCommand cmd = new SqlCommand("getclass", Conn);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlDataAdapter Da = new SqlDataAdapter(cmd);
            DataTable Dt = new DataTable();            Da.Fill(Dt);
            return Dt;
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }    public static DataTable getinittreetable()
    {
        try
        {            Open();            SqlCommand cmd = new SqlCommand("inittree", Conn);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlDataAdapter Da = new SqlDataAdapter(cmd);
            DataTable Dt = new DataTable();            Da.Fill(Dt);
            return Dt;
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }
    public static DataSet GetDataSet(string sql)
    {
        try
        {
            Open();
            SqlDataAdapter Da = new SqlDataAdapter(sql, Conn);
            DataSet Ds = new DataSet();
            Da.Fill(Ds);
            return Ds;
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }    public static DataTable GetDataTable(string sql)
    {
        try
        {
            Open();
            SqlDataAdapter Da = new SqlDataAdapter(sql, Conn);
            DataTable Dt = new DataTable();
            Da.Fill(Dt);
            return Dt;
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }    public static int ExecuteCmd(string sql)
    {
        try
        {
            Open();
            Cmd.CommandType = CommandType.Text;
            Cmd.CommandText = sql;
            Cmd.ExecuteNonQuery();
            return 1;
        }
        catch
        {
            return -1;
        }
        finally
        {
            Close();
        }
    }    /// <summary>
    /// 统计记录条数
    /// </summary>
    /// <param name="sql"></param>
    /// <returns></returns>
    public static int CountCmd(string sql)
    {
        try
        {
            Open();
            Cmd.CommandType = CommandType.Text;
            Cmd.CommandText = sql;
            return (int)Cmd.ExecuteScalar();
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }    public static DataTable getusertable(string user)
    {
        try
        {            Open();            SqlCommand cmd = new SqlCommand("getuserinfo", Conn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add("@user", SqlDbType.VarChar, 50);
            cmd.Parameters["@user"].Value = user;
            SqlDataAdapter Da = new SqlDataAdapter(cmd);
            DataTable Dt = new DataTable();            Da.Fill(Dt);
            return Dt;
        }
        catch (Exception e)
        {
            throw new Exception(e.Message, e);
        }
        finally
        {
            Close();
        }
    }    /// <summary>
    /// 判断管理员
    /// </summary>
    public static void IsAdmin(int lev)
    {
        /*
        string  user=HttpContext.Current.Session["UserName"].ToString();
        DataTable dtu = DataAccess.getusertable(user);
        int llev=3;
        if (Convert.ToInt16(dtu.Rows.Count) > 0)
        {
        llev = Convert.ToInt16(dtu.Rows[0]["GroupID"]);
        }
        if (llev != lev)
        {
        HttpContext.Current.Response.Write(@"<script>alert('用户身份不匹配，请不要使用旁注!');location='\\default.aspx';</script>");
        System.Web.HttpContext.Current.Response.End();
        }
       */            
    }
    public static string showgroupid(int lev)
    {
        switch (lev)
        {
            case 1: return "管理员"; break;
            case 2: return "教师"; break;
            case 3: return "学生"; break;
            default: return "学生";
        }    }    public static string showclass(int lev)
    {
        string Sql = "select * from ZDClass where ClassID=" + lev ;
        string classname=GetDataTable(Sql).Rows[0]["Classname"].ToString();
        return classname;    }    public static void Message(System.Web.UI.Page page, string nr)
    {        page.RegisterStartupScript("message", "<script language='javascript'>alert('" + nr + "');</script>");
      
       
    }
    public static void Message1(System.Web.UI.Page page, string nr, string Url)
    {        page.RegisterStartupScript("message", "<script language='javascript'>alert('" + nr + "'); location='" + Url + "'</script>");
    }    public static void Message2(System.Web.UI.Page page, string nr)
    {        page.RegisterStartupScript("message", "<script language='javascript'>alert('" + nr + "'); window.opener.reloadparent();self.close();</script>");
    }
    
    ///   <summary>   
    ///   判断是否为数字   
    ///   </summary>   
    ///   <param   name="myObj">传递的参数</param>   
    ///   <returns>返回真假值</returns>   
    public static bool isNumber(Object myObj)
    {
        try
        {
            int i = Convert.ToInt32(myObj);
            return (true);
        }
        catch
        {
            return (false);
        }
    }
}因为是边学边做的，很多都是从网上找来，修改下做出来的，
我知道问题肯定是出在数据库操作上，只是不知道怎么去修改，
请大虾指点啊！谢谢！！！！！！

Answer 3

DataAccess的所有数据库操作方法都加上
lock(typeof(DataAccess)){
...
}

Answer 4

你看看DataReader运行后没有关闭，估计不用50多人把，有一个人打开后第二个人在打就会出现这个问题吧。你逐步调试一下，把报错的地方一步一步修改

Answer 5

正解，有些列名并没有对上，比哪查询时没有name名，但前台绑定了name，或者查询是name但绑定的是namf还就是数据库要及时关闭，放进using中使用吧。建议你下载一个MSDN，看看USING的用法

Answer 6

我跟你一模一样的问题，困扰我好几天了，今天上午刚解决的，静态变量问题。
private static SqlConnection Conn = new SqlConnection();
private static SqlCommand Cmd = new SqlCommand();
千万不要定义成静态的，把它定义到方法里头去，什么时候用什么时候new对象实例化 调用连接串  这样每个人都会有自己的一个连接对象 再把web.config里面加上这个MultipleActiveResultSets=True这样写： <add name="userDB" connectionString="server=.;database=Media;uid=sa;pwd=sa;MultipleActiveResultSets=True"/>

Answer 7

感谢各位的支持
谢谢xiaoyatoupiqizhuai帮我解决了问题