为什么我的静态方法不能使用 using 语句？ [复制]

Question

如果我在一个类中这样使用它可以正常工作，当我从 default.cs 调用它时：

public class MyMethodsSql
{
    public static SqlDataReader MetodoCommand()
    {            
        string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
        SqlConnection con = new SqlConnection(CS);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "select * from Employees";
        con.Open();
        cmd.Connection = con;
        SqlDataReader sdr = cmd.ExecuteReader();

        return sdr;            
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    GridView1.DataSource = MyMethodsSql.MetodoCommand();
    GridView1.DataBind();
}

但是当我使用 using 语句时出现错误：表示没有打开的连接

 public class MyMethodsSql
 {
     public static SqlDataReader MetodoCommand()
     {            
         string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
         using (SqlConnection con = new SqlConnection(CS))
         {
             SqlCommand cmd = new SqlCommand();
             cmd.CommandText = "select * from Employees";
             con.Open();
             cmd.Connection = con;
             SqlDataReader sdr = cmd.ExecuteReader();

             return sdr;
         }
     }
 }

Answer 1

SQLConnection 将在返回数据读取器之前关闭/处理自己，数据读取器需要打开连接。