System.InvalidOperationException: 在没有任何数据时进行无效的读取尝试。

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 yd : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        if (Session["userinfo"] == null)
        {
            Response.Write("<script>alert('我是订餐页面！未授权用户不能访问');location='dl.aspx'</script>");

        }
        else
        {
            return ;

        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    { try
        {

        hyClass zc = new hyClass();
        zc = (hyClass)Session["userinfo"];

        string dcsj = TextBox1.Text.ToString();
        string dcsd = DropDownList2.Text.ToString();

        string czm = DropDownList1.Text.ToString();
        string sqltemp = "select czid,czm,czrs,czxx from cz where czm='" + czm.ToString() + "'";
        sql sc = new sql();
        SqlDataReader sr = sc.reader(sqltemp);


        string sqltem = "select dcid,dcsj,czid,hyid,dcsd from hy where czid='" + sr["czid"].ToString() + "' and dcsj='" + dcsj + "'and dcsd='" + dcsd + "'";

        sql sac = new sql();

        SqlDataReader sr1 = sac.reader(sqltem);

        if (sr1.Read())
        {
            Response.Write("<script>alert('已有人预定！');</script>");
        }
        else
        {
            string sqltem1 = "insert into  dc( dcsj,czid, hyid,dcsd) values ( '" + dcsj + "','" + sr["czid"].ToString() + "','" + zc.Hyid.ToString() + "','" + dcsd + "')";
            sql sxc = new sql();

            int t = sxc.nonquery(sqltem);
            if (t == 1)
            {

                Response.Write("<script>alert('添加成功');location='wjgl.aspx'</script>");
            }
            else
            {
                Response.Write("<script>alert('添加失败!');</script>");
            }
        }
        }
    catch (Exception ex)
    {
        Response.Write(ex);
    }
    }
}

报错信息
System.InvalidOperationException: 在没有任何数据时进行无效的读取尝试。在 System.Data.SqlClient.SqlDataReader.GetValue(Int32 i) 在 System.Data.SqlClient.SqlDataReader.get_Item(String name) 在 yd.Button1_Click(Object sender, EventArgs e) 位置 h:\订餐1\yd.aspx.cs:行号 49 --------------------编程问答--------------------

调试下这个方法 Button1_Click
看看参数和返回结果 --------------------编程问答-------------------- sr1 中没有数据，你去read报错 --------------------编程问答-------------------- 我知道 sr1 中没数据我是要建立判断，我想判断是否已有相同记录来处理下面操作。帮忙写一下判断代码 --------------------编程问答-------------------- int t = sxc.nonquery(sqltem);
->
int t = 0;
try { sxc.nonquery(sqltem); } catch { } --------------------编程问答-------------------- int t = sxc.nonquery(sqltem);
->
int t = 0;
try { t = sxc.nonquery(sqltem); } catch { } --------------------编程问答-------------------- 在哪来加？这个在 sr1查询中已经出错，我是想判断sr1中是否含有此数据来进行后面操作，麻烦帮我在上面代码改一下

补充：.NET技术 ,  ASP.NET