Why Large datatable in the case of crystal report is causing out of memory exception in IIS 7.5 ?

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C#2.0

C#

ASP.NET

CrystalReports

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Why Large datatable in the case of crystal report is causing out of memory exception in IIS 7.5? I am using asp.net with c#. The datatable is having around 4 lakh records. But the max limit is around 1 crore something.
So how to resolve this issue.

Crystal Report code as follows:

if(Session["ROLE"].ToString()=="C3O")

          {
                     ds = new ActiveCardsDetails().FetchAllActiveCardsDetails(startMonth, startYear, endMonth, endYear, corporateId,"C3O");
          }
          else
          {
                     ds = new ActiveCardsDetails().FetchAllActiveCardsDetails(startMonth, startYear, endMonth, endYear, corporateId,"C3");
          }


          DataTable dt = new DataTable();
          if (ds.Tables[0].Rows.Count > 0)
              dt = ds.Tables[0];
          else
          {
              Common.showMessage("No Records Found", this);
              return;
          }

          //--Initializing CrystalReport
          reportDocument = new ReportDocument();
          reportDocument.Load(reportPath);
          reportDocument.SetDataSource(dt);

          //Setting ParameterValues to report
          reportDocument.SetParameterValue("@p_FromMonth", startMonth);
          reportDocument.SetParameterValue("@p_ToMonth", endMonth);
          reportDocument.SetParameterValue("@p_FromYear", startYear);
          reportDocument.SetParameterValue("@p_ToYear", endYear);

          //--Binding report with CrystalReportViewer
          CRVActiveCardsDetails.ReportSource = reportDocument;
          CRVActiveCardsDetails.DataBind();
          Common.UserPageAudit(Session["User"].ToString(), "Active Cards Details", Session["ROLE"].ToString(), "Active Cards Details Report Viewed");