using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.Sql;
using System.Data.SqlClient;


public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
 
    protected void btnlogin_Click(object sender, EventArgs e)
    {
      
        SqlConnection con = DB.createCon();
        SqlCommand cmd = new SqlCommand();
         = "select count(*) from login where name='" + this.txtusername.Text + "'and password='" + this.txtpassword.Text+"'";
        cmd.Connection = con;
        SqlDataReader dr = cmd.ExecuteReader();
        
      
        if (dr.Read())
        {
           
            
            if ( txtusername==  && txtpassword=)错误就在这里使用 rows.[哪行][哪列] 还是使用string id pass;id= String id, pass;
             id. ==Convert.ToString(0);
            pass = dr.GetString(1);
            if (id == this.txtusername.Text && pass == this.txtpassword.Text)结果都达不到，请人帮帮忙看看怎么做！！！！！！！！！
            {
                Response.Write("<script>alert('登陆成功');location.href='index.aspx';</script>");
            }
            else { Response.Write("<script>alert('登陆失败,请核对你的用户名和密码 .');location.href='login.aspx';</script>"); }

            
        }
        else
        {
            Response.Write("<script>alert('登陆失败,请核对你的用户名和密码 .');location.href='login.aspx';</script>");
        }
    }

   
}
 

username=(string)dr[0];
password=(string)dr[1];
if (username == this.txtusername.Text && password == this.txtpassword.Text){...}

你的这个方法写的不好。。不过按照你的想法的话可以这样写
if (dr.Read())
        {
            if ( txtusername.Text==dr["name"].toString()  && txtpassword.Text=dr["password"].ToString())
            {
                Response.Write("<script>alert('登陆成功');location.href='index.aspx';</script>");
            }
            else { Response.Write("<script>alert('登陆失败,请核对你的用户名和密码 .');location.href='login.aspx';</script>"); }

不行啊，我懂你说的，但是我刚才试试，好像不行哦 错误的截图，是不是数据源出错了啊

还有要怎么做才比较好？请问

不行啊，还是有问题怎么办？啊，请教

大哥，你的问题就出在那里啊。。。你把那个(string)换掉
if(dr.Read())
{
    strings username=dr[0].ToString();
    string password=dr[1].ToString();
}
把类型转换放到后面就不出这个错误了

不好意思，这次回贴，回晚了点，有点事情