كد زير ارتباط 4 جدول در يه ديتاست رو برقرار ميكنه: 
dsService = new DataSet();



                //..................................................  .....................................



               SqlDataAdapter daService = new SqlDataAdapter("SELECT [SERVICE_Code] FROM [Tb_SERVICE] ", cnn);

                daService.Fill(dsService, "Tb_SERVICE");



               SqlDataAdapter daServiceList = new SqlDataAdapter("SELECT [ServiceList_Code],[ServiceList_ServiceCode] FROM [Tb_ServiceList]", cnn);

                daServiceList.Fill(dsService, "Tb_ServiceList");



               SqlDataAdapter daInsurance = new SqlDataAdapter("SELECT [INSURANCE_ID],[INSURANCE_Code],[INSURANCE_LIST_Code] FROM [Tb_INSURANCE]", cnn);

                daInsurance.Fill(dsService, "Tb_INSURANCE");



               SqlDataAdapter daInsList = new SqlDataAdapter("SELECT [InsList_Code],[InsList_INSURANCE_Code],[InsList_Name] FROM [Tb_InsList]", cnn);

                daInsList.Fill(dsService, "Tb_InsList");



                //..................................................  .....................................



               DataRelation drlServiceAndList = new DataRelation("ServiceAndList", dsService.Tables["Tb_SERVICE"].Columns["SERVICE_Code"], dsService.Tables["Tb_ServiceList"].Columns["ServiceList_ServiceCode"]);

                dsService.Relations.Add(drlServiceAndList);



               DataRelation drlListAndInsurance = new DataRelation("drlListAndInsurance", dsService.Tables["Tb_ServiceList"].Columns["ServiceList_Code"], dsService.Tables["Tb_INSURANCE"].Columns["INSURANCE_LIST_Code"]);

                dsService.Relations.Add(drlListAndInsurance);



               DataRelation drlInsuranceAndInsList = new DataRelation("drlInsuranceAndInsList", dsService.Tables["Tb_INSURANCE"].Columns["INSURANCE_Code"], dsService.Tables["Tb_InsList"].Columns["InsList_INSURANCE_Code"]);

                dsService.Relations.Add(drlInsuranceAndInsList);



                //..................................................  .....................................



               BindingSource bsService = new BindingSource(dsService, "Tb_SERVICE");

               BindingSource bsServiceList = new BindingSource(bsService, "ServiceAndList");

               BindingSource bsInsurance = new BindingSource(bsServiceList, "drlListAndInsurance");

               BindingSource bsInsList = new BindingSource(bsInsurance, "drlInsuranceAndInsList");



                //..................................................  .....................................





                dataGridViewXSERVICE.DataSource = bsService;



                dataGridViewXSERVICEList.DataSource = bsServiceList;



                dataGridViewXInsurance.DataSource = bsInsurance;



                dataGridViewXInsList.DataSource = bsInsList;

ببخشيد چون طولاني بود من فقط يه كم جمع و جورش كردم كه بشه خوندش ، نامها هم وقت نكردم تغيير بدم ، زياد پيچيده نيست.(اگه كسي هم بهينش كرد كه چه بهتر)