RLDC Report error : An error occurred during report processing.

[jasonalien]

I'm trying to generate a simple report based on this article : www.dotnetawesome.blogspot.com/2013/09/microsoft-report-in-mvc-4.html[^] Here is my controller

public ActionResult Report(string id)
{
LocalReport lr = new LocalReport();
string path = Path.Combine(Server.MapPath("~/Report"), "Person.rdlc");
if (System.IO.File.Exists(path))
{
lr.ReportPath = path;
}
else
{
return View("Index");
}
List cm = new List();

        var viewModel = new PersonIndexData();

        viewModel.People= db.Person
        .Include(k => k.Groups)
        .OrderBy(k => k.Name);

        cm = viewModel.People.ToList();

        ReportDataSource rd = new ReportDataSource("PersonDataSet", cm);
        lr.DataSources.Add(rd);
        string reportType = id;
        string mimeType;
        string encoding;
        string fileNameExtension;


        string deviceInfo =

        "" +
        "  " + id + "" +
        "  8.5in" +
        "  11in" +
        "  0.5in" +
        "  1in" +
        "  1in" +
        "  0.5in" +
        "";

        Warning\[\] warnings;
        string\[\] streams;
        byte\[\] renderedBytes;

        renderedBytes = lr.Render(
            reportType,
            deviceInfo,
            out mimeType,
            out encoding,
            out fileNameExtension,
            out streams,
            out warnings);


        return File(renderedBytes, mimeType);
    }

When I type (mysite/person/report/pdf), I get this exception : An error occurred during report processing. At this part :

    renderedBytes = lr.Render(
        reportType,
        deviceInfo,
        out mimeType,
        out encoding,
        out fileNameExtension,
        out streams,
        out wa