I want to show some data on every page with the layout (_Layout.cshtml), so I made a parent controller class, and the database access executes in its constructor. This works well except the case when I want to reach the session data, because when I try to check if the session variable exists, an exception (NullReferenceException) is thrown:
if (Session["UserId"] != null)
System.NullReferenceException: Object reference not set to an instance of an object.
I think that's because the Session object doesn't exist yet in the parent class. I can't find out another soluton to pass session related data to the layout, only when I copy the code to all action controllers. Any ideas?
Update:
Dave A, here is the parent class:
public class PCMarketController : Controller
{
protected PCMarketContext db = new PCMarketContext();
public PCMarketController()
{
int numberOfCartItems = 0;
if (Session["UserId"] != null) //Throws NullReferenceException in parent, works in action method
{
string UserId = HttpContext.Session["UserId"].ToString();
List<CartItem> CartItems = db.CartItems.Where(i => i.UserId == UserId).ToList();
foreach (var item in CartItems)
{
int count = item.Count;
numberOfCartItems += count;
}
}
ViewBag.NumberOfCartItems = " (" + numberOfCartItems + ")";
List<Category> Categories = db.Categories.ToList();
ViewBag.Categories = Categories;
}
}
You are correct in assuming the reason for Session to be null. The session HttpContext.Session injected at a later time in the page life cycle by the ControllerBuilder.
I would usually override OnActionExecuting method of the controller for such a case (http://msdn.microsoft.com/en-au/library/system.web.mvc.controller.onactionexecuting(v=vs.98).aspx).
One word of caution, using sessions may hinder the testability of your controller via standard unit tests
Cheers
Related
Here is what I'm trying to achieve. Certain options at the navbar should be available only if the user has "subordinates" in the database.
So, at the navbar I have:
The Approvals should be hidden for some users, but available to others. For those whom it should be available, the user must:
A) Be a Supervisor or,
B) Have a subornidate at the DB table
So, as for "A" it's pretty straightforward. I did:
#if (User.IsInRole("Supervisor"))
{
<li>#Html.ActionLink("Approvals", "Index", "Approval")</li>
}
For "B", I was suggested to use Sessions. Well, great. So I came to the question: how can I make a single request to the DB and assign it to a Session["HasSubordinates"] so I can do this check?
#if (User.IsInRole("Supervisor") || (bool)Session["HasSubordinates"])
{
<li>#Html.ActionLink("Approvals", "Index", "Approval")</li>
}
What I tried was to have:
Session["HasSubordinates"] = _uow.ApprovalService.GetSubordinates(User.Identity.Name).Count() > 0;
for every single controller, but that didn't worked well because sometimes I get null pointer and it looks absolutely rubbish.
I know it may sound like a trivial question for some (or most), but I'm really stuck and I do really appreciate any help.
Looking at your code, getting a user subordinates should only happen once. In your Login method:
Session["HasSubordinates"] = _uow.ApprovalService.GetSubordinates(User.Identity.Name).Count() > 0;
Create a new class to extend IPrincipal:
public class IPrincipalExtensions
{
public bool HasSubordinates(this IPrincipal user)
{
return Session != null && Session["HasSubordinates"] != null && Session["HasSubordinates"] > 0;
}
}
Now, in the View:
#if (User.IsInRole("Supervisor") || User.HasSubordinates() )
{
}
Writing from memory, may have left something out, but this should be the cleanest.
Don't use the session for this. What you need is a child action.
[ChildActionOnly]
public ActionResult Nav()
{
var model = new NavViewModel
{
IsSupervisor = User.IsInRole("Supervisor");
HasSubordinates = _uow.ApprovalService.GetSubordinates(User.Identity.Name).Count() > 0;
}
return ParialView("_Nav", model);
}
Then, just create a partial view, _Nav.cshtml and utilize the properties on the view model to render your nav however you like.
If you want, you can even use output caching on the child action, so it's only evaluated once per user. There's no built-in way to vary the cache by user, so first, you'll need to override the following method in Global.asax:
public override string GetVaryByCustomString(System.Web.HttpContext context, string custom)
{
var args = custom.ToLower().Split(';');
var sb = new StringBuilder();
foreach (var arg in args)
{
switch (arg)
{
case "user":
sb.Append(User.Identity.Name);
break;
case "ajax":
if (context.Request.Headers["X-Requested-With"] != null)
{
// "XMLHttpRequest" will be appended if it's an AJAX request
sb.Append(context.Request.Headers["X-Requested-With"]);
}
break;
default:
continue;
}
}
return sb.ToString();
}
With that, you can then just decorate your child action with:
[OutputCache(Duration = 3600, VaryByCustom = "User")]
Update I have saved my problem a long time ago. The problem was that I was trying to call the view model on the wrong view method! I was calling the base view method (Document), instead of one of it's derived method (like NewDocument, PDFDocument, etc.) Thus it was only giving me the Documents data, which didn't change. I was looking and using the wrong view method all the time... Stephen, when you asked me
"Why do you create derived classes in a method but then return only the base class"
I couldn't answer the question at the time because I didn't even know myself, until I remember that originally, the method wasn't returning the base class. I only changed it so that it can work with the base view method, which was wrong in the first place!
That's what I get for only getting 3-4 hours of sleep in 3 days. Everything works right now. Thanks.
I'm having a hard time trying to figure out why the data in my view isn't changing after I do a post. Originally I was doing it via return View() and it worked, but since it was a partial view, the page didn't look great, so I was reading up and saw that it was better to do it by Post-Redirect-Get pattern (PRG) and to use an id value to retrieve the values instead of sending the entire model via Tempdata. I even used ModelState.Clear() and that didn't even work. When I debugged the code, the model only has the values from when I first called it.
Here's part of my Get controller:
NewDocument Get Controller
[DocumentAuthenticationFilter]
public ActionResult NewDocument(int? id = null)
{
// This doesn't work. The view keeps on showing the data from View(Services.CreateNewDocument()).
if (id != null)
{
return View(Services.GetdocumentViewModelData(DocEnum.Section.NEW_DOC_INDEX, (int)id));
}
// This works fine
return View(Services.CreateNewDocument());
}
And here's the post that calls the redirect:
NewDocument Post controller
[HttpPost]
[ValidateAntiForgeryToken]
[MultipleButton(Name = "action", Argument = "AddDocuments")]
//[OutputCache(Duration = 30, VaryByParam = "*")]
public ActionResult AddDocumentViewModel(FormCollection frm, DocumentViewModel dvm)
{
try
{
if (ModelState.IsValid)
{
int? DocID = Services.AddingNewDocument(dvm);
// See, I even tried to clear it.
ModelState.Clear();
return base.RedirectToAction("NewDocument", new { id = DocID });
}
else
{
// Display errors in the modal
}
return base.RedirectToAction("NewDocument");
}
And here's the old way I did it:
NewDocument Post controller
[HttpPost]
[ValidateAntiForgeryToken]
[MultipleButton(Name = "action", Argument = "AddDocuments")]
//[OutputCache(Duration = 30, VaryByParam = "*")]
public ActionResult AddDocumentViewModel(FormCollection frm, DocumentViewModel dvm)
{
try
{
if (ModelState.IsValid)
{
Services.AddingNewDocument(ref dvm);
dvm.NewRecordMode = DocEnum.Action.UPDATE;
// It worked, but only the partial view showed, and not the entire view.
return PartialView("_NewDocument", dvm);
}
else
{
// Display errors in the model
}
return base.RedirectToAction("NewDocument");
}
Could it be because I'm using a custom model binding?
My Custom Model Binding
public class BaseClassModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var modelType = bindingContext.ModelType;
var modelTypeValue = controllerContext.Controller.ValueProvider.GetValue("ViewModel");
if (modelTypeValue == null)
throw new Exception("View does not contain the needed derived model type name");
var modelTypeName = modelTypeValue.AttemptedValue;
var type = modelType.Assembly.GetTypes().SingleOrDefault(x => x.IsSubclassOf(modelType) && x.Name == modelTypeName);
if (type == null)
{
throw new Exception(String.Format("Derived model type {0} not found", modelTypeName));
}
var instance = bindingContext.Model ?? base.CreateModel(controllerContext, bindingContext, type);
bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => instance, type);
return base.BindModel(controllerContext, bindingContext);
}
}
EDIT: And here's the GetDocumentViewModelData code:
GetDocumentFromViewModelData
public static DocumentViewModel GetDocumentViewModelData(DocEnum.Section docType, int id)
{
switch (docType)
{
case DocEnum.Section.NEW_DOCUMENT_INDEX:
// NewDocumentTypeViewModel is a child to DocumentTypeViewModel
DocumentTypeViewModel nd = NewDocumentService.GetViewModelByID(id);
return nd;
case DocEnum.Section.PDF_DOCUMENT:
DocumentTypeViewModel pdfvm = PDFDocumentService.GetViewModelByID(id);
return pdfvm;
case DocEnum.Section.XLS_DOCUMENT:
DocumentTypeViewModel xlsvm = XLSDocumentService.GetViewModelByID(id);
return xlsvm;
}
return null;
}
Edit: Also adding the GetViewModelByID function
GetViewModelByID
public static DocumentTypeViewModel GetViewModelByID(int id)
{
docEntities db = new docEntities();
NewDocumentTypeViewModel vm = new NewDocumentTypeViewModel();
// Calls a stored procedure called Select_Documents_ByID(id) to get the note entry
// that was submitted.
List<Select_Documents_ByID_Result> prevNotes = db.Select_Documents_ByID(id).ToList();
StringBuilder sNotes = new StringBuilder();
foreach (var note in prevNotes)
{
sNotes.AppendFormat("{0} - {1}: {2}\n\n", note.CreatedDate.ToString("yyyy-MM-dd HH:mm"), note.username, note.Entry);
}
vm.PreviousNotes = sNotes.ToString();
return vm;
}
Edit: I did a direct creation of the view model inside the Get controller, and it's the same result. when i debugged the view itself, the values from the new view model don't show up. Instead, the values from the initial view model, View(Services.CreateNewDocument()), shows.
[DocumentAuthenticationFilter]
public ActionResult NewDocument(int? id = null)
{
// Right here I created the view model to test thing, but I'm getting the same results. Nothing has changed.
if (id != null)
{
var d = new NewDocumentTypeViewModel(1, "Help!");
// This property is from the base class, DocumentTypeViewModel
d.DocumentTitle = "Testing!";
return View(d);
// Inside the view itself, none of the values in the view model, including the one
// belonging to the base class. It still shows the initial values.
}
// This works fine
// Or maybe not...
return View(Services.CreateNewDocument());
}
Edit: I wanted to see if it was also doing the same thing for the initial call to the view return View(Services.CreateNewDocument()), and decided to change the value for documentTitle in the base class from New Document to a randomly-generated number, after the object has been created.
Here's the code for DocumentTypeViewModel's default constructor:
public DocumentTypeViewModel()
{
DocumentTitle = "New Document";
NewRecordMode = DocEnum.Action.ADD;
DocumentID = 0;
}
And here's the Services.CreateNewDocument() code where I change the DocumentTitle after the View Model has been created.
public DocumentTypeViewModel CreateNewDocument()
{
DocumentTypeViewModel dtvm = new DocumentTypeViewModel();
Random r = new Random();
dtvm.DocumentTitle = r.Next(5, Int32.MaxValue).ToString();
return dtvm;
}
Now in the View, when I call DocumentTitle:
<div class="label-text-group">
#Html.LabelFor(model => model.DocumentTitle)
#Html.EditorFor(model => model.DocumentTitle)
</div>
You would expect to see a randomly-generated number every time the View gets called. Nope, what you would see is "New Document". Weird.
It's seems that Services.GetDocumentViewModelData() is not exactly working correctly. It only carries the values created by the base class' constructor when a view is created, not any values that have been added or changed within GetDocumentViewModelData() itself. Why is that? What's going on? Please help anybody!
I have solved it. Look at the Update section on top. Thanks Stephen.
I have method with code:
using (var cc = new MyDBContext())
{
var myList = (from user in cc.Users
where user.UserGroup.Name == "smth"
orderby user.ID ascending
select user);
if (startIndex != null)
return View(myList.Skip((int)startIndex).Take(50));
else
return View(myList);
}
In view I catch exception The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
Some people says that .ToList() must solve problem, but it throws an exception with myList.ToList() too. What is my problem?
P.S. in debug mode I have exception at #item.FullName in view, but if I move mouse on FullName property I can see correct value.
Sorry for my bad english.
Take the "return View()" statements outside of the "using" block completely. That will ensure you have retrieved the complete data sets before your DbContext object is disposed. Like this:
using (var cc = new MyDBContext())
{
var myList = (linq).ToList();
}
return View(myList);
I'm pretty sure the problem is that you are returning an IEnumerable to the View, which means the items haven't actually been retrieved yet. But when you return the object to your View, the DbContext is getting disposed before the view has a chance to retrieve the rows.
The problem was in lazy loaded sub property of User entity. I add to link statement Include("PropName") and it works good.
I'm not sure if this is a bug in the DefaultModelBinder class or what.
But UpdateModel usually doesn't change any values of the model except the ones it found a match for.
Take a look at the following:
[AcceptVerbs(HttpVerbs.Post)]
public ViewResult Edit(List<int> Ids)
{
// Load list of persons from the database
List<Person> people = GetFromDatabase(Ids);
// shouldn't this update only the Name & Age properties of each Person object
// in the collection and leave the rest of the properties (e.g. Id, Address)
// with their original value (whatever they were when retrieved from the db)
UpdateModel(people, "myPersonPrefix", new string[] { "Name", "Age" });
// ...
}
What happens is UpdateModel creates new Person objects, assign their Name & Age properties from the ValueProvider and put them in the argument List<>, which makes the rest of the properties set to their default initial value (e.g. Id = 0)
so what is going on here?
UPDATE:
I stepped through mvc source code (particularly DefaultModelBinder class) and here is what I found:
The class determines we are trying to bind a collection so it calls the method: UpdateCollection(...) which creates an inner ModelBindingContext that has a null Model property. Afterwards, that context is sent to the method BindComplexModel(...) which checks the Model property for null and creates a new instance of the model type if that is the case.
That's what causes the values to be reset.
And so, only the values that are coming through the form/query string/route data are populated, the rest remains in its initialized state.
I was able to make very few changes to UpdateCollection(...) to fix this problem.
Here is the method with my changes:
internal object UpdateCollection(ControllerContext controllerContext, ModelBindingContext bindingContext, Type elementType) {
IModelBinder elementBinder = Binders.GetBinder(elementType);
// build up a list of items from the request
List<object> modelList = new List<object>();
for (int currentIndex = 0; ; currentIndex++) {
string subIndexKey = CreateSubIndexName(bindingContext.ModelName, currentIndex);
if (!DictionaryHelpers.DoesAnyKeyHavePrefix(bindingContext.ValueProvider, subIndexKey)) {
// we ran out of elements to pull
break;
}
// **********************************************************
// The DefaultModelBinder shouldn't always create a new
// instance of elementType in the collection we are updating here.
// If an instance already exists, then we should update it, not create a new one.
// **********************************************************
IList containerModel = bindingContext.Model as IList;
object elementModel = null;
if (containerModel != null && currentIndex < containerModel.Count)
{
elementModel = containerModel[currentIndex];
}
//*****************************************************
ModelBindingContext innerContext = new ModelBindingContext() {
Model = elementModel, // assign the Model property
ModelName = subIndexKey,
ModelState = bindingContext.ModelState,
ModelType = elementType,
PropertyFilter = bindingContext.PropertyFilter,
ValueProvider = bindingContext.ValueProvider
};
object thisElement = elementBinder.BindModel(controllerContext, innerContext);
// we need to merge model errors up
VerifyValueUsability(controllerContext, bindingContext.ModelState, subIndexKey, elementType, thisElement);
modelList.Add(thisElement);
}
// if there weren't any elements at all in the request, just return
if (modelList.Count == 0) {
return null;
}
// replace the original collection
object collection = bindingContext.Model;
CollectionHelpers.ReplaceCollection(elementType, collection, modelList);
return collection;
}
Rudi Breedenraed just wrote an excellent post describing this problem and a very helpful solution. He overrides the DefaultModelBinder and then when it comes across a collection to update, it actually updates the item instead of creating it new like the default MVC behavior. With this, UpdateModel() and TryUpdateModel() behavior is consistent with both the root model and any collections.
You just gave me an idea to dig into ASP.NET MVC 2 source code.
I have been struggling with this for two weeks now. I found out that your solution will not work with nested lists. I put a breakpoint in the UpdateCollection method ,and it never gets hit. It seems like the root level of model needs to be a list for this method to be called
This is in short the model I have..I also have one more level of generic lists, but this is just a quick sample..
public class Borrowers
{
public string FirstName{get;set;}
public string LastName{get;set;}
public List<Address> Addresses{get;set;}
}
I guess that, I will need to dig deeper to find out what is going on.
UPDATE:
The UpdateCollection still gets called in asp.net mvc 2, but the problem with the fix above is related to this HERE
I'm doing some simple MS unit tests on my standard, nothing special controller.
When I check the ViewName proprty, from the returned ViewResult object, it's "" (empty).
I'm under the impression that the ViewName is implied by the name of the View (as suggested by this MS article on ASP.NET MVC controller testing).
BTW, when I test the ViewData, it's all there and correct.
Here's the code I have...
public ActionResult Index(int? page, string tag)
{
if (page == null || page <= 0)
{
page = 1;
}
var viewData = new IndexViewData
{
... my property setters, etc ...
};
return View(viewData);
}
[TestMethod]
public void Index_Action_Should_Return_Index_View_For_Default_HomePage()
{
// Arrange.
var controller = PostController; // Wrapper, cause I use D.I.
// Act.
ViewResult viewResult = controller.Index(null, null) as ViewResult;
// Assert.
Assert.IsNotNull(viewResult);
Assert.AreEqual("Index", viewResult.ViewName); // This is false/fails.
var indexViewData = viewResult.ViewData.Model as IndexViewData;
Assert.IsNotNull(indexViewData); // This is true.
}
The ViewName is only present when you set it in the ViewResult. If your View name matches your controller name, then I would check to ensure that the ViewName is null or empty as that would be (IMO) the correct behavior since you wouldn't want to set a name on the view. I only check that the ViewName is set when I intend that the View to be returned does not match the action -- say, when returning the "Error" view, for example.
EDIT: The following is the source for ExecuteResult in ViewResultBase.cs (from RC1, I don't have the source for RTW on my Macintosh). As you can see it checks to see if the ViewName has been set directly and if not, it pulls it from the action in the controller context's route data. This only happens in ExecuteResult, which is invoked AFTER your controller's action has completed.
public override void ExecuteResult(ControllerContext context) {
if (context == null) {
throw new ArgumentNullException("context");
}
if (String.IsNullOrEmpty(ViewName)) {
ViewName = context.RouteData.GetRequiredString("action");
}
ViewEngineResult result = null;
if (View == null) {
result = FindView(context);
View = result.View;
}
ViewContext viewContext = new ViewContext(context, View, ViewData, TempData);
View.Render(viewContext, context.HttpContext.Response.Output);
if (result != null) {
result.ViewEngine.ReleaseView(context, View);
}
}
I personally found the testing facilities provided by MVC2 to be somewhat clumsy. I'm guessing there is something better already extant, but I ended up creating a simple class to test actions. I modeled the interface (the implementation is another story) on a class provided by the excellent open source Java MVC framework Stripes called MockRoundTrip.
Here is the method used to get the action destination page when testing actions, called getTripDestination(). It returns the correct result irrespective of whether the viewname is explicitly set or not
//Get the destination page of the request, using Runtime execution pattern of MVC, namely
//if no ViewName is explicitly set in controller, ViewResult will have an empty ViewName
//Instead, current action name will be used in its place
public string getTripDestination()
{
RouteData routeData = getRouteData();
ViewResult viewResult = (result is ViewResult) ? (ViewResult)result : null;
string tripDestination = (viewResult != null) ? viewResult.ViewName : "";
return (tripDestination != "") ? tripDestination : (String)routeData.Values["action"];
}
private RouteData getRouteData()
{
HttpContextBase context = controller.ControllerContext.RequestContext.HttpContext;
return RouteTable.Routes.GetRouteData(context);
}
The viewname is set automatically by the framework. But when we unit test, we short-circuit the framework and there is nothing left to set the name.
So our actions need to set the viewname explicitly when we unit test. We could also check for null or empty if we really, really want to lean on the convention.
The documentation for Controller.View() states:
This method overload of the View class returns a ViewResult object
that has an empty ViewName property. If you are writing unit tests for
controller actions, take into account the empty ViewName property for
unit tests that do not take a string view name.
At run time, if the ViewName property is empty, the current action
name is used in place of the ViewName property.
So when expecting a view with the same name as the current action we can just test that it's an empty string.
Alternatively, the Controller.View(String) method will set the ViewName.