How to pass multiple parameters to a crystal report? - asp.net

Question

I have a crystal report in my asp.net web application which has a lot of report parameters (about 15). Previously I was using querystring to pass them but it was being unsecure.
Now I am mapping all parameters to a Hashtable, storing them in session & passing to the report viewer. Now If user opens multiple instance of reports in different browser tabs, the session values get messed up. When I navigate pages, wrong reports are displayed.
Please advise me a good method to pass my parameters to report.
Damien.

Answer 1

How about creating a simple DTO for storing all report parameters. Save this DTO in session and access in report viewer page where your viewer control resides.
To cross over the session issue when user opens multiple instances in browser, you can do a simple trick. When user provides parameter, and clicks on "Show Report", at that point create a guid, store value inside the session using key as this guid, and pass this guid as query string parameter to your report viewer page. This way each instance of report viewer page is aware which session value to be brought out.
Something like this
public class AttendanceDTO
{
public int EmployeeId {get;set;}
public string Month {get;set;}
}
And then in your "Report parameter page"
/* JUST NOTEPAD CODE, SYNTAX MIGHT VARY */
protected override ShowReport_Click(object sender, EventArgs e)
{
string guid = new Guid();
AttendanceDTO dto = new AttendanceDTO()
{ EmployeeId = txtEmployee.Text;
Month = txtMonth.text
};
session[guid] = dto;
Response.Redirect("ReportViewer.aspx?Guid=" + guid);
}
And then inside your Report Viewer Page
string guid = Request.QueryString["Guid"]; //Null check etc..
AttendanceDTO dto = (AttendanceDTO) session[guid];
//Provide dto values as parameters to your report viewer control and then clean the session
[You would need to make sure that you clear out the respective session value after you get it used.]
[Above code is just from notepad to give you an idea. On top of this you can bring more innovation]

Answer 2

Session Objects are shared among multiple tabs of same browser since server stores only one session cookie for a browser. So it is pretty obvious for the values to messup in several tabs on single browser.
One of the possible solution:
Use ViewStates instead of session to store HashTable.
Refer the code below for a demo, I have used ArrayList instead is HashTable for the sake of simplicity.
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ViewState["ht"] = new ArrayList();
//initialize viewstate with arraylist on first pageload.
}
}
protected void btnAddElement_Click(object sender, EventArgs e)
{//adding new elements to the arraylist
if (ViewState["ht"] != null)
{
ArrayList ht = (ArrayList)ViewState["ht"];
ht.Add(TextBox1.Text);
ViewState["ht"] = ht;
}
}
protected void Button2_Click(object sender, EventArgs e)
{
if (ViewState["ht"] != null)
{
ArrayList ht=(ArrayList)ViewState["ht"];
foreach (object a in ht)
{//write code to pass parameters to the crystal report
Response.Write(a);
}
}
}
}
Since Viewstates work at page level, therefor the values in the collection will not mess up this time.
Hope this helps.