XML document error / deserialize with C# SSRS web service

Hello,

I have a problem with this line : 

    _report = (Report)serializer.Deserialize(stream);

while trying to reproduce this : http://msdn.microsoft.com/en-us/library/aa337430.aspx (Load a Report Definition from the Report Server)

There is an error in XML document (2, 2) : <Report xmlns='http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition'> unexpected.

So I added : 

    XmlRootAttribute xRoot = new XmlRootAttribute();
                xRoot.ElementName = "Report";
                xRoot.Namespace = "http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition";
                xRoot.IsNullable = true;
                

but now I have :

The specified type is abstract : name='Report', namespace='http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition', for <Report xmlns='http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition'>.

(translated from french)

Many thanks in advance !

Alain

My code :

                        ReportingService2010 _reportService;

            _reportService = new ReportingService2010();
            _reportService.Credentials = new System.Net.NetworkCredential("Emeline", "2711");
            _reportService.Url ="http://localhost:8080/ReportServer/ReportService2010.asmx";


            string reportPath = "/report1";


            // Retrieve the report defintion 
            // from the report server

            Report _report;

            byte[] bytes =
                _reportService.GetItemDefinition(reportPath);


           ReportService2010.Warning[] warnings;

            //Create new report from report definition obtained in previous step and set datasource.
           // _reportService.CreateCatalogItem("Report", "CopiedReport", "/", false, bytes, null, out warnings);

            
            
            if (bytes != null)
            {

            
                
                XmlRootAttribute xRoot = new XmlRootAttribute();
                xRoot.ElementName = "Report";
                xRoot.Namespace = "http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition";
                xRoot.IsNullable = true;

                XmlSerializer serializer =
                    new XmlSerializer(typeof(Report),xRoot);

                
                // Load the report bytes into a memory stream
                using (MemoryStream stream = new MemoryStream(bytes))
                {
                    // Deserialize the report stream to an 
                    // instance of the Report class


                    XmlReader xmlReader = XmlReader.Create(stream);

                    XmlWriter xmlWriter;

                    using (xmlWriter = XmlWriter.Create("tmprep.xml"))
                    {

                        xmlWriter.WriteNode(xmlReader, false);

                    }
                                   


                    Response.Write("ready to deserialize");



                    stream.Position = 0;

                    _report = (Report)serializer.Deserialize(stream);

                    xmlReader.Close();

                }
            
            


            }

Versions : VS2012 / SQL2012 / REPORTBUILDER 3