dc.DeleteOnSubmit(dc.MyTables.Where(Function(x) x.id = 1).SingleOrDefault)
dc.DeleteAllOnSubmit(dc.MyTables)

[InvalidCastException: Specified cast is not valid.]
   System.Data.Linq.SingleKeyManager`2.TryCreateKeyFromValues(Object[] values, V& v) +59
   System.Data.Linq.IdentityCache`2.Find(Object[] keyValues) +28
   System.Data.Linq.StandardIdentityManager.Find(MetaType type, Object[] keyValues) +23
   System.Data.Linq.CommonDataServices.GetCachedObject(MetaType type, Object[] keyValues) +48
   System.Data.Linq.ChangeProcessor.GetOtherItem(MetaAssociation assoc, Object instance) +142
   System.Data.Linq.ChangeProcessor.BuildEdgeMaps() +233
   System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) +59
   System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) +331
   System.Data.Linq.DataContext.SubmitChanges() +19
   InpatientCensus.MaintenanceController.DeleteSoleCommunity(Int32 id) in C:Documents and SettingsgregfMy DocumentsProjectsInpatientCensusInpatientCensusControllersMaintenanceController.vb:14
   lambda_method(ExecutionScope , ControllerBase , Object[] ) +128
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +178
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +24
   System.Web.Mvc.<>c__DisplayClassa.<InvokeActionMethodWithFilters>b__7() +52
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +254
   System.Web.Mvc.<>c__DisplayClassc.<InvokeActionMethodWithFilters>b__9() +19
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +192
   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +399
   System.Web.Mvc.Controller.ExecuteCore() +126
   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +27
   System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7
   System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) +151
   System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) +57
   System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) +7
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

dc.MyTables.DeleteOnSubmit(dc.MyTables.SingleOrDefault(x=>x.id==1));
dc.MyTables.DeleteAllOnSubmit(dc.MyTables);