C# – ExportToHttpResponse gives : “Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.”

On load of ASP.Net page, a report function is called.

protected void Page_Load(object sender, EventArgs e)
{
    GlobalFunctions obj = new GlobalFunctions();
    obj.GetReport(Page PageName, string ReportName);
}

GetReport is defined as :

public void GetReport(Page PageName, string ReportName)
{
    ReportClass rpt = new ReportClass();
    rpt = GetReportFromDLL(ReportName);   //No error here
    rpt.ExportToHttpResponse(ExportFormatType.PortableDocFormat, Response, true, ReportName); 
}

Error :

"Response" is not accessible through the Class.

I have tried using "HttpContext.Current.Response" in place of "Response"

rpt.ExportToHttpResponse(ExportFormatType.PortableDocFormat,HttpContext.Current.Response, true, ReportName);

But I get this error:

"Unable to evaluate expression because the code is optimized or a
native frame is on top of the call stack."

Please help!