When I Click On The Button I Got This Error-->Invalid Cast From Datetime To Int32

public partial class updateuser : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["cnstr"].ConnectionString);
    SqlCommand cmd;
    SqlDataAdapter da;
    DataTable dt;
    DataSet ds;
    SqlDataReader dr;
    string str1 = "";
    private DateTime id;

protected void Button2_Click(object sender, EventArgs e)
   {


       con.Open();
       cmd = new SqlCommand("updateinfo", con);
       cmd.CommandType = CommandType.StoredProcedure;
       cmd.Parameters.Add("@id", SqlDbType.Int).Value = Convert.ToInt32(id);
       cmd.Parameters.Add("@fname", SqlDbType.VarChar).Value = fname.Text;
       cmd.Parameters.Add("@lname", SqlDbType.VarChar).Value = lname.Text;
       cmd.Parameters.Add("@mobile", SqlDbType.VarChar).Value = mbl.Text;
       cmd.Parameters.Add("@password", SqlDbType.VarChar).Value = pwd.Text;
       cmd.Parameters.Add("@confirmpassword", SqlDbType.VarChar).Value = pwd1.Text;
       cmd.Parameters.Add("@country", SqlDbType.VarChar).Value = country.SelectedIndex;
       cmd.Parameters.Add("@state", SqlDbType.VarChar).Value = state.SelectedIndex;
       cmd.Parameters.Add("@city", SqlDbType.VarChar).Value = city.SelectedIndex;
       cmd.Parameters.Add("@birth_date", SqlDbType.VarChar).Value = dob.Text.Trim();
       cmd.Parameters.Add("@bloodgrp", SqlDbType.NChar).Value = blood.SelectedIndex;
       cmd.Parameters.Add("@gender", str1);
       dt = new DataTable();
       da = new SqlDataAdapter(cmd);
       da.Fill(dt);
       int s = Convert.ToInt32(dt.Rows[0][0]);
       if (s == 1)
       {

           Response.Redirect("userhome.aspx");

       }
       else
       {
           errmsg.Text = "Update Faild";

           con.Close();
       }
       if (RadioButton1.Checked)
       {
           str1 = "Male";
       }
       if (RadioButton2.Checked)
       {
           str1 = "Female";
       }
}