<add name="ContractDataEntities" 
connectionString="metadata=res://*/ModelData.csdl|res://*/ModelData.ssdl|res://*/ModelData.msl;provider=System.Data.SqlClient;
provider connection string=&quot;data source=(LocalDB)\v11.0;
attachdbfilename=|DataDirectory|\ContractData.mdf;integrated security=True;MultipleActiveResultSets=True;
App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
 

 string Pass = dataMod.UserData.SingleOrDefault(x => x.Id == 1).Pass;

 
ContractDataEntities dataMod = dataMod = new ContractDataEntities();

                var nElement = new UserData
                {
                    Pass = "123",
                    Login = "123",
                };

                dataMod.UserData.Add(nElement);
                dataMod.SaveChanges();

  UserData item = dataMod.UserData.SingleOrDefault(x => x.Id == 1);
                item.Pass = tbNewPAss.Text;
                item.Login = "Юра";
                dataMod.SaveChanges();