crystal report viewer print and export button not work in c#.net 4.0

Quote:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;//for ReportDocument

namespace WebApplicationTraining.Reports
{
public partial class ProjectReportWithPara : System.Web.UI.Page
{
SqlConnection Con = new SqlConnection(ConfigurationManager.ConnectionStrings["MainDB"].ConnectionString);
SqlCommand cmd = new SqlCommand();

#region Help Method
private void ProjectDataBind()
{
DataSet ds = new DataSet();
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
try
{
Con.Open();
cmd.CommandText = "sp_Project_SelectAll";
cmd.CommandType = CommandType.StoredProcedure;

cmd.Connection = Con;

adapter.Fill(ds, "tbl_Project");
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
cmd.Dispose();
if (Con.State != ConnectionState.Closed)
Con.Close();
}
//DataTable dt = controller.SelectAll();
cboFromProject.DataTextField = "Project";
cboFromProject.DataValueField = "ProjectID";
cboFromProject.DataSource = ds.Tables[0];
cboFromProject.DataBind();

}
private void ToProjectDataBind()
{
DataSet ds = new DataSet();
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
try
{
Con.Open();
cmd.CommandText = "sp_Project_SelectAll";
cmd.CommandType = CommandType.StoredProcedure;

cmd.Connection = Con;

adapter.Fill(ds, "tbl_Project");
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
cmd.Dispose();
if (Con.State != ConnectionState.Closed)
Con.Close();
}
//DataTable dtable = controller.SelectAll();
cboToProject.DataTextField = "Project";
cboToProject.DataValueField = "ProjectID";
cboToProject.DataSource = ds.Tables[0];//dtable;
cboToProject.DataBind();
}
public DataSet getFromTOProjects(int fproject, int toproject)
{

//string sqlCon = ConfigurationManager.AppSettings["MainDB"].ToString();

DataSet ds = null;
SqlDataAdapter adapter;
try
{
Con.Open();
cmd.CommandText = "sp_projectReport_ByProject";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new SqlParameter("@fproject", fproject));
cmd.Parameters.Add(new SqlParameter("@toproject", toproject));
cmd.Connection = Con;
ds = new DataSet();
adapter = new SqlDataAdapter(cmd);
adapter.Fill(ds, "tbl_Project");
//adapter.Fill(ds);
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
cmd.Dispose();
if (Con.State != ConnectionState.Closed)
Con.Close();
}
return ds;
}
#endregion
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ProjectDataBind();
ToProjectDataBind();
}
if (IsPostBack)
{
try
{
CrystalReportViewer2.ReportSource = (ReportDocument)Session["Report"];
//CrystalReportViewer2.RefreshReport(); write this code,will prompt
//CrystalReportViewer2.DataBind();
}
catch (Exception ex)
{

// throw;
}
}

}

protected void btnPreview_Click(object sender, EventArgs e)
{

ReportDocument rptDoc = new ReportDocument();
DataSet ds = new DataSet();
DataTable dtable = new DataTable();
dtable.TableName = "tbl_Project";
ds = getFromTOProjects(Convert.ToInt32(cboFromProject.SelectedValue), Convert.ToInt32(cboToProject.SelectedValue));
dtable = ds.Tables[0];

rptDoc.Load(Server.MapPath("~\\Reports\\ProjectReportWithPara.rpt"));
rptDoc.SetDataSource(dtable);
rptDoc.SetParameterValue("ReportTitle", "Project Report By Project");
rptDoc.SetParameterValue("FromProject", cboFromProject.SelectedItem.Text);
rptDoc.SetParameterValue("ToProject", cboToProject.SelectedItem.Text);


Session["Report"] = rptDoc;
CrystalReportViewer2.ReportSource = rptDoc;

// can print and export but prompt already set parameters
//CrystalReportViewer2.ReuseParameterValuesOnRefresh = false;
//CrystalReportViewer2.DataBind();
//CrystalReportViewer2.ReportSource = rptDoc.Clone();
//CrystalReportViewer2.RefreshReport();

}
}
}