HI. I trying to populate dropdownlist with values in the database in asp.net. But its not working:(

web.config


   
 



using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
namespace WebApplication2
{
  public partial class WebForm1 : System.Web.UI.Page
  {
  string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
  protected void Page_Load(object sender, EventArgs e)
  {
  SqlConnection con = new SqlConnection(strConnString);
  SqlCommand cmd = new SqlCommand("select * from Student1", con);
  SqlDataAdapter da = new SqlDataAdapter(cmd);
  DataSet ds = new DataSet();
  da.Fill(ds);
  DropDownList1.DataTextField = ds.Tables[0].Columns["FullName"].ToString();
  DropDownList1.DataValueField = ds.Tables[0].Columns["Id"].ToString();
  DropDownList1.DataSource = ds.Tables[0];
  DropDownList1.DataBind();
  }
  }
}

Use Connection string name as well in web.config and use namespec

like
using System.Configuration;

AND

 SqlConnection con = new SqlConnection(
ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString);
        SqlCommand cmd = new SqlCommand("select * from Student1", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        drpdownlist.DataTextField = ds.Tables[0].Columns["FullName"].ToString();
        drpdownlist.DataValueField = ds.Tables[0].Columns["Id"].ToString();
        drpdownlist.DataSource = ds.Tables[0];
        drpdownlist.DataBind();

Now it is giving this error :

An attempt to attach an auto-named database for file H:\Practice\WebApplication1\WebApplication1\App_Data\aspnetdb.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.