Use Session to store Report and Use its Solve your Problem.
Look at Code
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
Session.Remove("CR_Session");
Session.Clear();
BindReport();
}
CrystalReportViewer1.ReportSource = Session["CR_Session"];
}
void BindReport()
{
HR_EmployeeVocation Cr = new HR_EmployeeVocation();
Cr.SetDataSource(GetEmployeeList());
Session.Add("CR_Session", Cr);
}