用户代码未处理无效的操作异常

Question

Hello guys can someone pls give me help here I'm newbie and I don't know what to do! the error is point to the SqlDataReader rdr = cmd.ExecuteReader() it says ,

An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code

My codes is in below. Thanks in advance.

EmpListModel

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Collections;

namespace AIStestv01.Models
{
    public class EmpListModel
    {
        public string BioID { get; set; }
        public string Fullname { get; set; }
        public string Dthired { get; set; }
        public string DeptID { get; set; }
        public string Active { get; set; }
        public string NTLogin { get; set; }
    }
}

EmpController

using AIStestv01.Models;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Web;
using System.Web.Mvc;

namespace AIStestv01.Controllers.AdminControllers
{
public class EmpController : Controller
{
    // GET: Emp
    public ActionResult Index()
    {
        var con = ConfigurationManager.ConnectionStrings["WOPcon"].ConnectionString;
        using (SqlConnection conObj = new SqlConnection(con))
        {
            SqlCommand cmd = new SqlCommand("wsp_Test01", conObj);
            cmd.CommandType = System.Data.CommandType.StoredProcedure;

            var model = new List<EmpListModel>();
            using (SqlConnection conn = new SqlConnection(con))
            {
                conn.Open();
                SqlDataReader rdr = cmd.ExecuteReader(); //it says this is the error
                while (rdr.Read())
                {
                    var emp = new EmpListModel();
                    emp.BioID = Convert.ToString(rdr["BioID"]);
                    emp.Fullname = Convert.ToString(rdr["Fullname"]);
                    emp.Dthired = Convert.ToString(rdr["Dthired"]);
                    emp.DeptID = Convert.ToString(rdr["DeptID"]);
                    emp.Active = Convert.ToString(rdr["Active"]);
                    emp.NTLogin = Convert.ToString(rdr["NTLogin"]);

                    model.Add(emp);
                }
            }
        }

        return View();
    }
}

}

Index.cshtml

@model IEnumerable<AIStestv01.Models.EmpListModel>  

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index</h2>

<table>
    <tr>
        <th>Bio ID</th>
        <th>FUllname</th>
        <th>Date Hired</th>
        <th>Dept ID</th>
        <th>Active</th>
        <th>NT LOgin</th>
    </tr>
    @foreach (var emp in Model)
    {
        <tr>
            <td>@Html.DisplayFor(modelItem => emp.BioID)</td>
            <td>@Html.DisplayFor(modelItem => emp.Fullname)</td>
            <td>@Html.DisplayFor(modelItem => emp.Dthired)</td>
            <td>@Html.DisplayFor(modelItem => emp.DeptID)</td>
            <td>@Html.DisplayFor(modelItem => emp.Active)</td>
            <td>@Html.DisplayFor(modelItem => emp.NTLogin)</td>
        </tr>
    }
</table>

Answer 1

You have two using statements with the SqlConnection creation. In your SqlCommand, cmd, you are using the first connection - conObj, but you open with the conn.Open() the second connection. Leave out the second SqlConnection using, and open the first one. Also it is ok to put in the using the SqlDataReader creation.

Edit: As suggested by NightOwl888 to point out the issue with the connection not opened, this is the changed code. Edit 2: I've changed the return statement to include model list into the returning view.

using AIStestv01.Models;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Web;
using System.Web.Mvc;

namespace AIStestv01.Controllers.AdminControllers
{
    public class EmpController : Controller
    {
        // GET: Emp
        public ActionResult Index()
        {
            var con = ConfigurationManager.ConnectionStrings["WOPcon"].ConnectionString;
            using (SqlConnection conObj = new SqlConnection(con))
            {
                SqlCommand cmd = new SqlCommand("wsp_Test01", conObj);
                cmd.CommandType = System.Data.CommandType.StoredProcedure;

                var model = new List<EmpListModel>();

                conObj.Open();//Openning of the connection associated with the sql command

                using (SqlDataReader rdr = cmd.ExecuteReader())//Using around the SqlDataReader to dispose it after use
                {
                    while (rdr.Read())
                    {
                        var emp = new EmpListModel();
                        emp.BioID = Convert.ToString(rdr["BioID"]);
                        emp.Fullname = Convert.ToString(rdr["Fullname"]);
                        emp.Dthired = Convert.ToString(rdr["Dthired"]);
                        emp.DeptID = Convert.ToString(rdr["DeptID"]);
                        emp.Active = Convert.ToString(rdr["Active"]);
                        emp.NTLogin = Convert.ToString(rdr["NTLogin"]);

                        model.Add(emp);
                    }
                }
            }

            //do something with the 

            return View(model);//added model to use it in cshtml
        }
    }
}

Answer 2

First of all, you don't need two connections to perform this operation. A single connection will do the trick. Second, it seems the problem is related to the Data Type of the fields returned by your query. Try using a '?.ToString()' instead of that Convert.ToString. Also, consider handling the data type that comes from the database. For instance, DateTime columns can be converted to DateTime in C#, then you can use ToString('format') to extract the value.

Another suggestion is to remove all columns from your Data Reader loop, and start adding one by one, so you can isolate the one that is causing the issue.