ASP.NET 、 SqlDataReader 和 SqlCommand （已经有一个打开的 DataReader 与此命令关联，必须先关闭）

Question

我收到此错误：

已经有一个打开的 DataReader 与此命令关联，必须先关闭它。

我不知道问题出在哪里。它关闭了，但仍然说它是开放的。请帮忙！

第一个命令是获取所有在两个日期之间有假期的员工。

第二个命令我用它来按 ID 检索日期。

这是我的代码：

using (SqlConnection con = new SqlConnection(connection))
{
     con.Open();

     SqlCommand cmd = new SqlCommand(" SELECT distinct E.EmployeeId, E.FirstName FROM Employee E INNER JOIN Vacation V ON E.EmployeeId = V.EmployeeId " +
                                     " WHERE ((V.Dates >= @Start AND V.Dates <= @End) ) ", con);
     cmd.Parameters.AddWithValue("@Start", (Calendar1.SelectedDates[0]).Date.ToShortDateString());
     cmd.Parameters.AddWithValue("@End", (Calendar1.SelectedDates[Calendar1.SelectedDates.Count - 1]).Date.ToShortDateString());

    using (SqlDataReader dr = cmd.ExecuteReader())
    {
        while (dr.Read())
        {
             Response.Write((dr[1]).ToString() + "  "); // Check if retrieves employee name
             // Now by Id I want to get all dates belong to specific employee
             SqlCommand cmd2 = new SqlCommand("SELECT V.Dates FROM Vacation V " +
                                              " WHERE ((V.Dates >= @Start AND V.Dates <= @End) ) ", con);
             cmd2.Parameters.AddWithValue("@Start", (Calendar1.SelectedDates[0]).Date.ToShortDateString());
             cmd2.Parameters.AddWithValue("@End", (Calendar1.SelectedDates[Calendar1.SelectedDates.Count - 1]).Date.ToShortDateString());
             cmd2.Parameters.AddWithValue("@EmployeeId", Convert.ToInt32(dr[0]));                                    

             using (SqlDataReader dr2 = cmd2.ExecuteReader())
             {
                 while (dr2.Read())
                 {
                      Response.Write(Convert.ToDateTime(dr2[0]));
                 }
             }

             Response.Write("<br/>");
         } 

         GridView7.DataSource = cmd.ExecuteReader();
         GridView7.DataBind();
    }
    con.close();
}

Answer 1

将此添加到您的连接字符串：

MultipleActiveResultSets=True