Want to make Func<UnknownType, bool> where UnknownType is only known at runtime

Question

So, I'm experimenting with expressions atm. Got code below: Code works fine except for 1 thing: I need to replace ViewModel type with ForeignKeyProperty.PropertyType, which is only known at runtime, at the line of var condition = Expression.Lambda < Func < ViewModel, bool> >

Expected end result:

ForeignKeyProperty.SetValue(model, repository.GetList  <ForeignKeyProperty.PropertyType >().Single(x => x.Id == model.Id));

protected List < Action < IVenturaRepository, ViewModel>> SetForeignKeyProperties<ViewModel>() where ViewModel : BaseViewModel
        {
            var viewModelType = typeof(ViewModel);
            var foreignKeyProperties = viewModelType.GetProperties().Where(x => x.PropertyType.IsSubclassOf(typeof(BaseViewModel)));
            var actions = new List < Action < IVenturaRepository, ViewModel>>();
            var repositoryType = typeof(IVenturaRepository);
            foreach(var ForeignKeyProperty in foreignKeyProperties)
            {
                var foreignKeyIdProperty = viewModelType.GetProperties().SingleOrDefault(x => x.Name == ForeignKeyProperty.Name + "Id");
                //ForeignKeyProperty.SetValue(model, repository.GetList<ViewModel>().Single(x => x.Id == model.Id));
                var listMethod = repositoryType.GetMethods().SingleOrDefault(x => x.Name == "GetList").MakeGenericMethod(ForeignKeyProperty.PropertyType);
                //Expression.Call(singleMethod,);
                var repositoryVariable = Expression.Parameter(repositoryType, "repository");
                var paramViewModelType = Expression.Parameter(viewModelType, "model");
                var paramForeignEntityId = Expression.Property(paramViewModelType, "Id");
                var listMethodCall = Expression.Call(repositoryVariable, listMethod);
                var modelParameter = Expression.Parameter(ForeignKeyProperty.PropertyType, "x");
                var foreignKeyTypeConstant = Expression.Constant(ForeignKeyProperty.PropertyType);
                var condition =
                    Expression.Lambda < Func < ViewModel, bool>>(
                        Expression.Equal(
                            Expression.Property(paramViewModelType, foreignKeyIdProperty.Name),
                            Expression.Convert(Expression.Property(modelParameter, "Id"),foreignKeyIdProperty.PropertyType)
                        ),
                        modelParameter
                    );
                //var singleMethod = typeof(Enumerable).GetMethods().SingleOrDefault(x => x.Name.Equals("SingleOrDefault") && x.GetParameters().Count() ==2).MakeGenericMethod(viewModelType);
                //var singleMethod = typeof(IEnumerable<ViewModel>).GetMethods().SingleOrDefault(x => x.GetParameters().Count() > 0).MakeGenericMethod(viewModelType);
                //var singleLambda = Expression.Lambda(Expression.Property(modelParameter, "Id"), modelParameter);
                var singleMethodCall = Expression.Call(typeof(Enumerable), "SingleOrDefault", new[] { ForeignKeyProperty.PropertyType },listMethodCall, condition);
                //var singleMethodCall = Expression.Call(listMethodCall, singleMethod, condition);
                var setMethod = ForeignKeyProperty.GetSetMethod();
                var oParameter = Expression.Parameter(viewModelType, "obj");
                var vParameter = Expression.Parameter(typeof(ViewModel),"value");
                var method = Expression.Call(oParameter,setMethod, singleMethodCall);
                var expression = Expression.Lambda<Action<IVenturaRepository, ViewModel>>(method);
                actions.Add(expression.Compile());
            }
            return actions;
        }

Could someone point me in the right direction please?

Answer 1

use Object as type. then you can check type by getType() at runtime and after check cast to correct type. or use dynamic to avoid casting.

Answer 2

So, I did as you suggested and used object instead. It works now. Code below works in a specific controller that inherits from BaseController. public override ActionResult Edit(long id, DeliveryEditViewModel model) { model.SourceModel.DeliveryRound = Repository.DeliveryRounds.Single(x => x.Id == model.DeliveryRoundId); model.SourceModel.Sale = Repository.Sales.Single(x => x.Id == model.SaleId); return base.Edit(id, model); } public override ActionResult Edit(long id, DeliveryEditViewModel model) { model.SourceModel.DeliveryRound = Repository.DeliveryRounds.Single(x => x.Id == model.DeliveryRoundId); model.SourceModel.Sale = Repository.Sales.Single(x => x.Id == model.SaleId); return base.Edit(id, model); } Idea is that code below works in BaseController: public virtual ActionResult Edit(long id, EditModel model) { try { if (setForeignKeyActionList == null) setForeignKeyActionList = SetForeignKeyProperties(); setForeignKeyActionList.ForEach(action => action(Repository, model.SourceModel)); Repository.SaveItem(model); return RedirectToAction("Index"); } catch(Exception ex) { ModelState.AddModelError("Error", ex); return View(Repository.GetEditableItem(id)); } } public virtual ActionResult Edit(long id, EditModel model) { try { if (setForeignKeyActionList == null) setForeignKeyActionList = SetForeignKeyProperties(); setForeignKeyActionList.ForEach(action => action(Repository, model.SourceModel)); Repository.SaveItem(model); return RedirectToAction("Index"); } catch(Exception ex) { ModelState.AddModelError("Error", ex); return View(Repository.GetEditableItem(id)); } }

This is the revised code based on your suggestion to use object type protected List< Action< IVenturaRepository, ViewModel>> SetForeignKeyProperties() { var viewModelType = typeof(ViewModel); var foreignKeyProperties = viewModelType.GetProperties().Where(x => x.PropertyType.IsSubclassOf(typeof(BaseViewModel))); var actions = new List< Action< IVenturaRepository, ViewModel>>(); var repositoryType = typeof(IVenturaRepository); foreach (var ForeignKeyProperty in foreignKeyProperties) { var foreignKeyIdProperty = viewModelType.GetProperties().SingleOrDefault(x => x.Name == ForeignKeyProperty.Name + "Id"); //ForeignKeyProperty.SetValue(model, repository.GetList< OtherViewModel>().Single(x => x.Id == model.Id)); var listMethod = repositoryType.GetMethods().SingleOrDefault(x => x.Name == "GetList").MakeGenericMethod(ForeignKeyProperty.PropertyType); var repositoryVariable = Expression.Parameter(repositoryType, "repository"); var paramViewModelType = Expression.Parameter(viewModelType, "model"); var paramForeignEntityId = Expression.Property(paramViewModelType, "Id"); var listMethodCall = Expression.Call(repositoryVariable, listMethod); protected List< Action< IVenturaRepository, ViewModel>> SetForeignKeyProperties() { var viewModelType = typeof(ViewModel); var foreignKeyProperties = viewModelType.GetProperties().Where(x => x.PropertyType.IsSubclassOf(typeof(BaseViewModel))); var actions = new List< Action< IVenturaRepository, ViewModel>>(); var repositoryType = typeof(IVenturaRepository); foreach (var ForeignKeyProperty in foreignKeyProperties) { var foreignKeyIdProperty = viewModelType.GetProperties().SingleOrDefault(x => x.Name == ForeignKeyProperty.Name + "Id"); //ForeignKeyProperty.SetValue(model, repository.GetList< OtherViewModel>().Single(x => x.Id == model.Id)); var listMethod = repositoryType.GetMethods().SingleOrDefault(x => x.Name == "GetList").MakeGenericMethod(ForeignKeyProperty.PropertyType); var repositoryVariable = Expression.Parameter(repositoryType, "repository"); var paramViewModelType = Expression.Parameter(viewModelType, "model"); var paramForeignEntityId = Expression.Property(paramViewModelType, "Id"); var listMethodCall = Expression.Call(repositoryVariable, listMethod);

  var foreignKeyTypeConstant = Expression.Constant(ForeignKeyProperty.PropertyType); var objectType = Expression.Parameter(typeof(object), "model"); var modelParameter = Expression.Parameter(typeof(object), "x"); var expressionForeignKeyId = Expression.Property(paramViewModelType, foreignKeyIdProperty.Name); var expressionForeignEntityId = Expression.Convert(Expression.Property(Expression.Convert(modelParameter, ForeignKeyProperty.PropertyType), "Id"), foreignKeyIdProperty.PropertyType); var condition = Expression.Lambda<Func<object, bool>>( Expression.Equal( expressionForeignKeyId, expressionForeignEntityId ), modelParameter ); var singleMethodCall = Expression.Call(typeof(Enumerable), "SingleOrDefault", new[] { ForeignKeyProperty.PropertyType }, listMethodCall, condition); //var singleMethodCall = Expression.Call(listMethodCall, singleMethod, condition); var setMethod = ForeignKeyProperty.GetSetMethod(); //var oParameter = Expression.Parameter(viewModelType, "obj"); var vParameter = Expression.Parameter(typeof(ViewModel), "value"); var method = Expression.Call(paramViewModelType, setMethod, singleMethodCall); var lamdaParameterExpressions = new[] { repositoryVariable, paramViewModelType }; var expression = Expression.Lambda<Action<IVenturaRepository, ViewModel>>(method, lamdaParameterExpressions); actions.Add(expression.Compile()); } return actions; }