How do I link the main report with the subreport RDLC asp.net Core

 Local Report  version  : ReportViewerCore.NETCore  15.1.17

Report Name : rptDepartment.rdlc, rptEmployeeDemoDetails.rdlc

Data Source : 

Sub Report Added

Sub Report Configuration

 public class HomeController : Controller   

{
        private List GetEmployeeDemoList = new List()
        {
                new EmployeeDemo() {ID = 1, Name = "Sam", Gender ="male", Email="[email protected]"},
                new EmployeeDemo() {ID = 1, Name = "Ella",Gender ="female", Email="[email protected]" },
                new EmployeeDemo() {ID = 1, Name = "TG",Gender ="male", Email ="[email protected]" },
                new EmployeeDemo() {ID = 1, Name = "Favor",Gender ="female", Email="[email protected]" },
                new EmployeeDemo() {ID = 2,Name = "Micheal",Gender ="male",Email ="[email protected]" },
                new EmployeeDemo() {ID = 2, Name = "Joe",Gender ="male", Email ="[email protected]" },
                new EmployeeDemo() {ID = 2, Name="Maintain",Gender ="female",Email ="[email protected]" },
                new EmployeeDemo() {ID = 3, Name = "Akeem",Gender ="male", Email ="[email protected]" },
                new EmployeeDemo() {ID = 3, Name = "Boye",Gender ="male", Email ="[email protected]" },
                new EmployeeDemo() {ID = 4, Name ="Chioma",Gender ="female",Email ="[email protected]" },
                new EmployeeDemo() {ID = 4, Name = "Ofure",Gender ="female", Email ="[email protected]" },
                new EmployeeDemo() {ID = 4, Name = "Hart",Gender ="male",Email ="[email protected]" }
        };

        private List departments = new List()
        {
               new Department() {ID = 1, Name = "Applied Mathematics" },
               new Department() {ID = 2, Name = "Software" },
               new Department() {ID = 3, Name = "Machine Learning" },
               new Department() {ID = 4, Name = "Petroleum Engineering" },
        };

        private readonly ILogger _logger;
        private readonly IWebHostEnvironment _webHostEnviorment;

        public HomeController(ILogger logger, IWebHostEnvironment webHostEnviorment)
        {
            _logger = logger;
            _webHostEnviorment = webHostEnviorment;
            System.Text.Encoding.RegisterProvider(System.Text.CodePagesEncodingProvider.Instance);
        }

        public IActionResult Index()
        {
            return View();
        }
        public IActionResult Print()
        {
            string renderFromat = "pdf";
            string mimetype = "application/pdf";
            string extension = "pdf";

            Dictionary parameter = new Dictionary();
            parameter.Add("ReportParameter1", "Well Come to RDLC Report");
            LocalReport localReport = new LocalReport();
            localReport.ReportPath= $"{this._webHostEnviorment.WebRootPath}\\Reports\\Report1.rdlc";
            var pdf = localReport.Render(renderFromat);
            return File(pdf, mimetype, "report." + extension);
        }

        public IActionResult PrintReport()
         {
            string renderFromat = "PDF";
            string extension = "pdf";
            string mimetype = "application/pdf";
            using var report = new LocalReport();
          //  var dt = new DataTable();
            var  dt =departments;
            report.DataSources.Add(new ReportDataSource("Department_DS", dt));
            var parameters = new[] { new ReportParameter("prm1", "RDLC Sub-Report Example") };
            report.ReportPath = $"{this._webHostEnviorment.WebRootPath}\\Reports\\rptDepartment.rdlc";
            report.SetParameters(parameters);

            //For Sub Type =======>>>
            report.SubreportProcessing += new SubreportProcessingEventHandler(subReportProcessing);

            var pdf = report.Render(renderFromat);
            return File(pdf, mimetype, "report." + extension);
        }

        void subReportProcessing(object sender,SubreportProcessingEventArgs e)
        {
            var ID = Convert.ToInt32(e.Parameters[0].Values[0]);
          //  var employeegroup = Employees.FindAll(x => x.ID == ID);

           int empId = Convert.ToInt32((e.Parameters["ID"].Values[0].ToString()));
            //var dt2 = GetEmployeeDetailsList().Select("EmpId=" + empId);

            var dt = GetEmployeeDemoList;

            var result = dt.FindAll(x => x.ID == empId);
            var res = result;
            ReportDataSource ds = new ReportDataSource("EmployeeDemo_DS", result);
            e.DataSources.Add(ds);
        }

    }

Report Dowanload

My Git Hub Link 

https://github.com/MH-Abir97/RDLC