My Crystal Report is not getting refreshed while passing parameter?

public partial class Reports_MyCrystalReport: System.Web.UI.Page
{
 SqlConnection sqlCon = new SqlConnection(ConfigurationManager.AppSettings["MYAPP"]);
 ReportDocument objCrystalReport = new ReportDocument();

 string Username = ConfigurationManager.AppSettings["RptUserName"];
 string Password = ConfigurationManager.AppSettings["RptPassword"];

 protected void Page_Init(object sender, EventArgs e)
    {
        objCrystalReport.Load(Server.MapPath("MyCrystalReport.rpt"));
        objCrystalReport.SetDatabaseLogon(Username, Password, @"DATABASE 
        SERVER NAME", "DATABASE NAME");
        CrystalReportViewer1.ReportSource = objCrystalReport ;              
        CrystalReportViewer1.DisplayToolbar = true;
        CrystalReportViewer1.HasPrintButton = true;
        CrystalReportViewer1.HasCrystalLogo = false;
    }
 protected void Page_Unload(object sender, EventArgs e)
    {
        objCrystalReport.Close();
        objCrystalReport.Dispose();
    }
}