ODBC Error

I am using Crystal Reports 9.0. In order to establish connectivity with SQL Server 2008, I have created a user DSN, selected the server path, the database and its credentials. The connection was successful, When I open the any report in Crystal Reports editor, I am able to work with the database.

But when I call the report in C#

public static void ExportToPdf(ReportDocument selectedReport, ArrayList PrmListName, ArrayList PrmListValue, string reportName, CrystalDecisions.Shared.ExportFormatType eft)
{
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
selectedReport.ExportToHttpResponse(eft, HttpContext.Current.Response, true, reportName);
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
}

This is the exception that is coming.

{CrystalDecisions.CrystalReports.Engine.LogOnException: Logon failed.
Details: IM002:[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
Error in File C:\Windows\TEMP\rptE2Cert {AE5834BB-2936-43B7-9DF6-A5DDCA9D73AE}.rpt:
Unable to connect: incorrect log on parameters. ---> System.Runtime.InteropServices.COMException (0x8004100F): Logon failed.
Details: IM002:[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
Error in File C:\Windows\TEMP\rptE2Cert {AE5834BB-2936-43B7-9DF6-A5DDCA9D73AE}.rpt:
Unable to connect: incorrect log on parameters.
   at CrystalDecisions.ReportAppServer.Controllers.ReportSourceClass.Export(ExportOptions pExportOptions, RequestContext pRequestContext)
   at CrystalDecisions.ReportSource.EromReportSourceBase.ExportToStream(ExportRequestContext reqContext)
   --- End of inner exception stack trace ---
   at CrystalDecisions.ReportAppServer.ConvertDotNetToErom.ThrowDotNetException(Exception e)
   at CrystalDecisions.ReportSource.EromReportSourceBase.ExportToStream(ExportRequestContext reqContext)
   at CrystalDecisions.CrystalReports.Engine.FormatEngine.ExportToStream(ExportRequestContext reqContext)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.ExportToStream(ExportOptions options)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.ExportToHttpResponse(ExportOptions options, HttpResponse response, Boolean asAttachment, String attachmentName)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.ExportToHttpResponse(ExportFormatType formatType, HttpResponse response, Boolean asAttachment, String attachmentName)
   at Gaselec.GenerateReport.ExpCRToPDF.ExportToPdf(ReportDocument selectedReport, ArrayList PrmListName, ArrayList PrmListValue, String reportName, ExportFormatType eft) in D:\Projects\NewGE3\APP_CODE\BLL\ExpCRToPDF.cs:line 117}

Can someone tell me solution to this issue? When I am able to use database in the Crystal Reports, while using it in database expert. Why is it happening in the code?