Crystal Reports Error : Missing parameter field current value

Message

   Hi. 
Please help me resolve this error."Missing parameter field current value". Error here crReportDocument.Export()
Code:
Private Sub Btn_Export_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btn_Export.Click
Dim exportFileName As String = "iCalls_CrystalReport_Department.rpt"
Dim exportPath As String = "D:\SampleCrystalReports\iCalls_Export\test1.pdf"
Dim crExportOptions As ExportOptions
Dim crDestOptions As New DiskFileDestinationOptions
crDestOptions.DiskFileName = exportPath
crExportOptions = crReportDocument.ExportOptions
crExportOptions.DestinationOptions = crDestOptions
crExportOptions.ExportDestinationType = ExportDestinationType.DiskFile
crExportOptions.ExportFormatType = ExportFormatType.PortableDocFormat
crReportDocument.Export()
End Sub
Moreover this code will Export - from where i can Print. But Can anyone pls help me with the code in vb.net from where i can 'Print' directly from the local Printer.