i am getting this error on my laptop when i am trying to run this code which by the way runs perfectly on my friends computer.plz help the server where i am supposed to run this code also gives...

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

public partial class Default2 : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection();
    
    protected void Page_Load(object sender, EventArgs e)
    {
        con.ConnectionString = "server=a2ul-pc;uid=sa;pwd=rascal;database=cgrt";
        if (con.State == ConnectionState.Closed)
        {
            con.Open();
        }
        if (Page.IsPostBack == false)
        {
            string query = "select * from project";
            SqlCommand cmd = new SqlCommand(query, con);
            cmd.CommandType = CommandType.Text;
            SqlDataAdapter adp = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            adp.Fill(ds);
            DropDownList1.DataSource = ds;
            DropDownList1.DataValueField = ds.Tables[0].Columns[1].ToString();
            DropDownList1.DataTextField = ds.Tables[0].Columns[1].ToString();
            DropDownList1.DataBind();
            DropDownList1.Items.Insert(0, "--Select--");
            cmd.Dispose();
        }

        con.Close();
        
      

    }
    protected void Button1_Click(object sender, EventArgs e)
    {

       
           string str = "select  
m.pcode,m.fyyear,m.date,m.salary,m.ta,m.contigency,m.nrc,m.institcharges,m.others,p.total from monthly m inner join project p where m.pcode="+DropDownList1.SelectedItem.Value.ToString()+"on p.pcode=m.pcode";
            SqlDataAdapter da = new SqlDataAdapter(str, con);
            DataTable dt = new DataTable();
            da.Fill(dt);
            GridView1.DataSource = dt;
            GridView1.DataBind();
       
        
    }
}