You can't leave RDLC witout DataSets, if you are using it and RDLC is embedded in your project. Either you leave DataSet fixed and change only it's items either try to load report definition from XML
// Valid XML with dynamic DataSources and DataSets
string s = @"<?xml version=""1.0"" encoding=""utf-8""?><Report ...>...</Report>";
report.LoadReportDefinition(new MemoryStream(Encoding.UTF8.GetBytes(s)));
return report.Render(reportName);