System.InvalidOperationException: 已有打开的与此命令相关联的 DataReader，必须首先将它关闭。

[renye0907]

源错误:


行 35: SqlDataAdapter da = new SqlDataAdapter(str, conn);
行 36: DataSet ds = new DataSet();
行 37: da.Fill(ds, "score");
行 38: DataGrid1.DataSource = ds;
行 39: DataGrid1.DataBind();


源文件: e:\kechen\tcmg.aspx.cs 行: 37

  
string strcon = "data source=www-51f7b2a9835\\sqlexpress;initial catalog=student;integrated security=SSPI";
        SqlConnection conn = new SqlConnection(strcon);
        conn.Open();
        string sel="select * from teacher where t_no='"+TextBox2 .Text .ToString ().Trim ()+"'and t_pas ='"+TextBox1 .Text.ToString ().Trim () +"'";
        SqlCommand cmd = new SqlCommand(sel, conn);
        SqlDataReader read = cmd.ExecuteReader();
        conn.Close();
        if (read.Read())
        {
           LinkButton1.Visible = true;
            LinkButton2.Visible = true;
            string str = "SELECT score.c_no, sco.s_no, sco.score FROM score INNER JOIN sco ON score.c_no = sco.c_no";
            SqlDataAdapter da = new SqlDataAdapter(str, conn);
            DataSet ds = new DataSet();
            da.Fill(ds, "score");
            DataGrid1.DataSource = ds;
            DataGrid1.DataBind();
        }
        else
        {
            Label1.Text = "帐号或密码有错误";
        }

[barry_bai]

最后加上
read.close();

[ysw830]

你的代码好像有多处错误，conn.Close();连接关闭了，是不能执行read.Read()操作的，应当等执行完read.Read()在关闭，或在程序最后关闭。执行完read.Read()后，记得要用read.close();关闭read对象。还有“score.c_no = sco.c_no”应该是“score.c_no = sco.s_no”
string strcon = "data source=www-51f7b2a9835\\sqlexpress;initial catalog=student;integrated security=SSPI";
SqlConnection conn = new SqlConnection(strcon);
conn.Open();
string sel="select * from teacher where t_no='"+TextBox2 .Text .ToString ().Trim ()+"'and t_pas ='"+TextBox1 .Text.ToString ().Trim () +"'";
SqlCommand cmd = new SqlCommand(sel, conn);
SqlDataReader read = cmd.ExecuteReader();

if (read.Read())
{
read.Close();
LinkButton1.Visible = true;
LinkButton2.Visible = true;
string str = "SELECT score.c_no, sco.s_no, sco.score FROM score INNER JOIN sco ON score.c_no = sco.s_no";
SqlDataAdapter da = new SqlDataAdapter(str, conn);
DataSet ds = new DataSet();
da.Fill(ds, "score");
DataGrid1.DataSource = ds;
DataGrid1.DataBind();
}
else
{
Label1.Text = "帐号或密码有错误";
}
conn.Close();
你再试试！