Cannot implicitly convert "System.Data.SqlClient.SqlDataReader" to "SqlDataReader.SqlDataReader"

Question

I am new to C#. Just following Kudvenkat tutorials for beginners. I get an error on this line:

SqlDataReader rdr = cmd.ExecuteReader();

Something to do with ExecuteReader();

I am sure its something simple, but could you please explain why does it happens?

My aspx.cs file

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace SqlDataReader
{
    public partial class SqlDataReader : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            // creating variable that holds value of connection string 
            string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;

            // creating connection object with use of "using" block
            using (SqlConnection con = new SqlConnection(CS))
            {
                con.Open();

                SqlCommand cmd = new SqlCommand("select top 5 ProductID, LocationID,Shelf,Quantity from [Production].[ProductInventory]", con);

                SqlDataReader rdr = cmd.ExecuteReader();   // --Error

                GridView1.DataSource = rdr;
                GridView1.DataBind();
            }
        }
    }
}

My aspx file:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="SqlDataReader.aspx.cs" Inherits="SqlDataReader.SqlDataReader" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

    </div>
        <asp:GridView ID="GridView1" runat="server" BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px" CellPadding="3" CellSpacing="2">
            <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
            <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
            <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
            <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
            <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
            <SortedAscendingCellStyle BackColor="#FFF1D4" />
            <SortedAscendingHeaderStyle BackColor="#B95C30" />
            <SortedDescendingCellStyle BackColor="#F1E5CE" />
            <SortedDescendingHeaderStyle BackColor="#93451F" />
        </asp:GridView>
    </form>
</body>
</html>

Try to name your class (and also namespace) to other name, your class name SqlDataReader just the same as the official one, which C# don't know which you are using — Prisoner
– Prisoner, Commented Feb 1, 2017 at 4:30
Or you could just do: var rdr = cmd.ExecuteReader(); or better: System.Data.SqlClient.SqlDataReader rdr = cmd.ExecuteReader();. Of course the best practice is to rename your namespace as @Prisoner suggests. — Keyur PATEL
– Keyur PATEL, Commented Feb 1, 2017 at 4:35

sujith karivelil · Accepted Answer · 2017-02-01 04:34:39Z

1

It was because of the name of your class and the namespace, the compiler assumes that rdr is of type SqlDataReader which is your class name under namespace SqlDataReader. So the best option here is Rename your class, Alternative option also for you is fully qualified names. which means you have to specify the namespace of the class as well while instantiating the class, ie., the code will be like this:

System.Data.SqlClient.SqlDataReader rdr = cmd.ExecuteReader(); // No Error now

Another option for you is make use of static type definer, var by using this type will be automatically assigned to store the value that we are assiging to them, that is :

var rdr = cmd.ExecuteReader(); // No Error now

Here rdr will be of type what ExecuteReader() method is returing.

answered Feb 1, 2017 at 4:34

sujith karivelil

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1 Comment

sujith karivelil Over a year ago

@Oleg: Happy to help you

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