Windowsapplication1.form1.fillcombobox--system.NullReference.Exception

[sivakrishna546]

hai, when i working with windows apllication i got following runtime error:
Object reference is not to set an instance of object :
at cmb_eno.Items.A dd(dr[0]).can any one help me?

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        SqlConnection con;
        SqlDataAdapter da;
        DataSet ds;
        DataTable dt;
        public Form1()
        {
            con = new SqlConnection();
            con.ConnectionString = " Data Source=SIVA-496EA1B239\\SQLEXPRESS;Initial Catalog=Inventory;Persist Security Info=True;User ID=sa;Password=abcd1234";

            da = new SqlDataAdapter("select * from emp", con);
            ds = new DataSet();
            da.Fill(ds, "emp");
           dt = ds.Tables[0];
            fillcombobox();         
            InitializeComponent();
        }
         void fillcombobox()
        {
           
            DataRow[] drs = dt.Select(null);
            foreach (DataRow dr in drs)
            {

             cmb_eno.Items.Add(dr[0].ToString());
         
            }
        }

        public void bt_get_Click(object sender, EventArgs e)
        {
            
            DataRow[] drs = dt.Select(null);
            string str = " ";
            foreach (DataRow dr in drs)
            {
                str += dr[0] + "\t";
                str += dr[1] + "\t";
                str += dr[2] + "\n";

            }
            MessageBox.Show(str);
        }

        private void eno_cmb_SelectedIndexChanged(object sender, EventArgs e)
        {
            DataRow[] drs = dt.Select("Empno = " + eno_cmb.Text);
            DataRow dr =  drs[0];
            ename_txt.Text= dr["empname"].ToString();
            esalary_txt.Text = dr["empsalary"].ToString();
        
            
        }
        

    }
    
}

[kenobewan]

Try using a messagebox to display the value and debug from there.