Sub-report won't show up - "The subreport 'subreport1' could not be found at the specific location ..."

Hi, I've got an ASP.NET project which includes a report (main.rdlc). This report has a sub-report (mySubReport.rldc). Both are set as embedded resources in their properties.
The report runs fine but the subreport does not show up. It comes with the message, on the report itself:

The subreport 'subreport1' could not be found at the specific location /Project_Name Reports/mySubReport. Please verify that the subreport has been published and the name is correct.

Also, when I check the outputwindow I can see the following warning:

Warning: An error occurred while executing the subreport 'Subreport1' (Instance: 0): The report definition for report 'mySubReport' has not been specified (rsErrorExecutingSubreport)

  protected void btnReport_Click(object sender, EventArgs e)
        {
            Warning[] warnings;
            string[] streamIds;
            string mimeType = string.Empty;
            string encoding = string.Empty;
            string extension = string.Empty;

           

            var cnn = new SqlConnection(Global.conString);

            ReportViewer viewer = new ReportViewer();
            viewer.ProcessingMode = ProcessingMode.Local;
  
            viewer.LocalReport.ReportPath = "Reports/Main.rdlc";
            viewer.LocalReport.EnableExternalImages = true;

            
            // viewer.LocalReport.SubreportProcessing += new SubreportProcessingEventHandler(addsubreport);

           
 	     // 1st data source	
           SqlCommand cmd = new SqlCommand("StoreProcedure", cnn);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = cmd;
            DataSet ds = new DataSet();

            SqlParameter param = cmd.Parameters.AddWithValue("@Param1", "value1");
            param.SqlDbType = SqlDbType.Int;

            SqlParameter p2 = cmd.Parameters.AddWithValue("@Param2", "value2");

            da.Fill(ds);
            DataTable dt = new DataTable();
            dt = ds.Tables[0];


            // 2nd data source
            SqlCommand cmd2 = new SqlCommand("SELECT * FROM Table1", cnn);
            cmd2.CommandType = CommandType.Text;
            SqlDataAdapter da2 = new SqlDataAdapter();
            da2.SelectCommand = cmd2;
            DataSet ds2 = new DataSet();

            Da2.Fill(ds2);
            DataTable dt2 = new DataTable();
            Dt2 = ds2.Tables[0];



            ReportParameter[] p = new ReportParameter[2];
            p[0] = new ReportParameter("Para,1", "value1", false);
            p[1] = new ReportParameter("Param2", "value2", false);


            ReportDataSource rds = new ReportDataSource("DataSet1", dt);
            viewer.LocalReport.DataSources.Add(rds);
          

            ReportDataSource rdsPapers = new ReportDataSource("ds2", dt2);
            viewer.LocalReport.DataSources.Add(rdsPapers);
            viewer.LocalReport.SetParameters(p);

            viewer.LocalReport.Refresh();


              byte[] bytes = viewer.LocalReport.Render("PDF", null, out mimeType, out encoding, out extension, out streamIds, out warnings);

            Response.Buffer = true;
            Response.Clear();
            Response.ContentType = mimeType;
            Response.AddHeader("content-disposition", "attachment; filename=" + "testReport" + "." + extension);
            Response.BinaryWrite(bytes);
            Response.Flush();
        }

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I added this line to the code above but the event is not triggering:

      viewer.LocalReport.SubreportProcessing += new SubreportProcessingEventHandler(addsubreport);

Any ideas on this?