asp mvc wcf Validation failed for one or more entities

Question

I am writing an application that imports from excel and save in database using asp.net mvc and wcf

Controller

        [HttpPost]
    public JsonResult UploadExcel(FIRS firs, HttpPostedFileBase FileUpload)
    {

        List<string> data = new List<string>();
        if (FileUpload != null)
        {
            // tdata.ExecuteCommand("truncate table OtherCompanyAssets");  
            if (FileUpload.ContentType == "application/vnd.ms-excel" || FileUpload.ContentType == "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
            {


                string filename = FileUpload.FileName;
                string targetpath = Server.MapPath("~/FileUpload/");
                FileUpload.SaveAs(targetpath + filename);
                string pathToExcelFile = targetpath + filename;
                var connectionString = "";
                if (filename.EndsWith(".xls"))
                {
                    connectionString = string.Format("Provider=Microsoft.Jet.OLEDB.4.0; data source={0}; Extended Properties=Excel 8.0;", pathToExcelFile);
                }
                else if (filename.EndsWith(".xlsx"))
                {
                    connectionString = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0 Xml;HDR=YES;IMEX=1\";", pathToExcelFile);
                }

                var adapter = new OleDbDataAdapter("SELECT * FROM [Sheet1$]", connectionString);
                var ds = new DataSet();

                adapter.Fill(ds, "ExcelTable");

                DataTable dtable = ds.Tables["ExcelTable"];

                string sheetName = "Sheet1";

                var excelFile = new ExcelQueryFactory(pathToExcelFile);
                var firsRecords = from a in excelFile.Worksheet<FIRS>(sheetName) select a;

                foreach (var a in firsRecords)
                {
                    try
                    {
                        if (a.RC_NUMBER != "" && a.TIN_NUMBER != "" && a.COMPANY_NAME != "" && a.TCC_NUMBER != "")
                        {
                            FIRS TU = new FIRS();
                            var helper = new FirsServiceClient();
                            TU.RC_NUMBER = a.RC_NUMBER;
                            TU.TIN_NUMBER = a.TIN_NUMBER;
                            TU.COMPANY_NAME = a.COMPANY_NAME;
                            TU.TCC_NUMBER = a.TCC_NUMBER;
                            //db.FIRS.Add(TU);
                            //_firsService.AddFirs(TU);
                            //svc.SaveFirsImportData(TU);
                            //helper.SaveFirsImportData(TU);
                            TU.ACTION_STATUS = 1;
                            TU.CREATED_DATE = DateTime.Now;

                            _firsService.AddFirs(firs);

                        }
                        else
                        {
                            data.Add("<ul>");
                            if (a.RC_NUMBER == "" || a.RC_NUMBER == null) data.Add("<li> RC Number is required</li>");
                            if (a.TIN_NUMBER == "" || a.TIN_NUMBER == null) data.Add("<li>RC Number is required</li>");
                            if (a.COMPANY_NAME == "" || a.COMPANY_NAME == null) data.Add("<li>Company Name is required</li>");
                            if (a.TCC_NUMBER == "" || a.TCC_NUMBER == null) data.Add("<li> TCC Number is required</li>");
                            data.Add("</ul>");
                            data.ToArray();
                            return Json(data, JsonRequestBehavior.AllowGet);
                        }
                    }

                    catch (DbEntityValidationException ex)
                    {
                        foreach (var entityValidationErrors in ex.EntityValidationErrors)
                        {

                            foreach (var validationError in entityValidationErrors.ValidationErrors)
                            {

                                Response.Write("Property: " + validationError.PropertyName + " Error: " + validationError.ErrorMessage);

                            }

                        }
                    }
                }
                //deleting excel file from folder  
                if ((System.IO.File.Exists(pathToExcelFile)))
                {
                    System.IO.File.Delete(pathToExcelFile);
                }
                return Json("success", JsonRequestBehavior.AllowGet);
            }
            else
            {
                //alert message for invalid file format  
                data.Add("<ul>");
                data.Add("<li>Only Excel file format is allowed</li>");
                data.Add("</ul>");
                data.ToArray();
                return Json(data, JsonRequestBehavior.AllowGet);
            }
        }
        else
        {
            data.Add("<ul>");
            if (FileUpload == null) data.Add("<li>Please choose Excel file</li>");
            data.Add("</ul>");
            data.ToArray();
            return Json(data, JsonRequestBehavior.AllowGet);
        }
    }

Service.svc

        public void AddFirs(FIRS firs)
    {
        _firsManager.AddFirs(firs);
    }

When upload excel is click from view, it calls the controller ** public JsonResult UploadExcel(FIRS firs, HttpPostedFileBase FileUpload)** Then, the controller reference the service AddFirs(FIRS firs) to save data to the database.

Why am I getting this error, and how can I resolve it.