I'm using NerdDinner as a guide for my first MVC/LINQ to SQL project. It discusses the use of the ViewModel pattern when a View needs data from multiple sources - in their example: Dinners and Countries (serves as the drop down list).
In my application, the problem is a bit different. It's not so much different data, rather data linked via a key constraint. I have a Story table that links to aspnet_users via the UserId key. I would like to have easy access to the UserName for each story.
Since I'm using the repository pattern and returning IQueryable in some cases for deferred execution, I'm struggling with the correct way to shape the data. So I'm using this VideModel pattern right now to make it work but not sure if it's the right way.
Instead of returing IQueryable Story (which wouldn't work since I need the UserName), I'm returning a new custom class UserStory, which has a Story property and a string Username property.
What are your thoughts?
It seems like your question has less to do with MVC as it is simply a question about how to access the story data based on the username string.
Would it be possible to create a view in your database with all the UserStory data, the username, along with userid in it? That way, you could select from the view based on the username you have.
To create the view, you would simply have to do a join between the user table and the userstory table based on the userid.
After that, you could still use the repository pattern with the IQueryable being returned.
If you are wanting to do updates, it would be simple to do since you still have the userid, and would be able to link back to the actual table which would need the update.
If you look at Kigg, you will see that they mess about with the initial model to create custom ViewModels. That's the thing that NerdDinner doesn't cover in any detail. You could create a StoriesWithUserName class that inherits from Stories, but adds a new property - UserName. Then you return that to your View which would inherit from IEnumerable<StoriesWithUserName>
[EDIT]
Oops. Didn't spot that you already did this :o)
Using the repository pattern and returning an IQueryable of Stories is fine. The relationship allows you to access the the username value something like this >>
Assuming you are returning the IQueryable in your model object:
foreach(Story story in Model.Stories)
{
// do something with the value
response.write(story.aspnet_user.UserName);
};
Your Repository method would look like this:
public List<Stories> GetStories(Guid UserId)
{
return datacontext.Stories.Where(u => u.UserId = UserId).ToList();
}
The relationship will automatically provide you with access to the UserName value in the foreach loop i first mentioned. nothing more is required.
I'm not sure why your pagination control failed on Count() though??
Hope this helps
Related
I'm using EF database first and with MVC.
I'm wanting to add some validation on a property to compare its old value to its new one and report a validation error to the MVC ModelState if there is a problem.
This would be easy enough using code first and validating using 'set' on the property. However I can't do this using database first because its auto generated.
I've looked at using IValidatableObject and the validate() method however by then the value has already been changed on the property so I can't see the old one anymore to compare to.
Short of creating a method to pass the new value into first to check it, I can't think of another way.
Any suggestions?
Thanks
If you want to compare a new value to an old value then you are going to have to grab the values from the database first (before updating) and compare them:
[HttpPost]
public ActionResult Update(MyObject myObject)
{
var oldObject = db.Objects.FirstOrDefault(o => o.Id == myObject.Id);
//Compare oldObject.Value to myObject.Value
}
You could still use IValidatebleObject and pass in the objects that you need to keep that logic outside the controller.
Its not the ideal and this has started illustrating some of the weaknesses in Model and DB first but here's how I ended up doing it.
I decided to change the property in my model so that set was private and then create a separate method in the partial class to set the value. The validation is then all done in that method.
Thanks for your help anyway
I've had a thorough search around but really can't find anything addressing the scenario I'm facing (oddly because I'd have thought it's quite a common thing to do).
Background
I'm creating an application with ASP.NET MVC 4 and Entity Framework 5 Code First. For the purpose of this question, think of it as a blogging application with posts and users.
Project
The post model requires that every post have a corresponding UserId.
With the ASP.NET MVC 4 Membership it is easy to find the username of the person logged in with
User.Identity.Name.
This isn't ideal, we want the ID, but a query such as this can search the db for the name and get the ID.
db.UserProfiles.Single(a => a.UserName == User.Identity.Name);
Problem
The problem arises when trying to create a post. Model.IsValid is false, as no UserId is being passed in from the view. Obviously, as the user isn't expected to enter their ID.
I've tried putting the ID value into the ViewBag and using a #Html.Hidden() field in the view, however I've had no success with this. Model.IsValid always returns false.
Should this information be input through the create view? Or should it be done directly in the controller? Its quite a frustrating problem as I have the information and just need to figure how to pass it into the model.
CONTROLLER CODE
This is basically just the default scaffolded code. The commented code is how I tried setting the model value directly from the controller, however that was little more than trial and error.
//
// POST: /Post/Create
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(Post post)
{
if (ModelState.IsValid)
{
//var userId = db.UserProfiles.Single(a => a.UserName == User.Identity.Name);
//post.User.UserId = userId.UserId;
db.Posts.Add(post);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(post);
}
Be careful with hidden fields. Anyone could put whatever value they want in that field (i.e. they could spoof another user). You'd be better off caching the ID in the session at login, and using that value.
This is a typical case where you want to create an EditModel as a data transfer object (DTO) between your view and controller layers.
Create a class BlogPostEditModel that has all properties you need the user to fill in when creating a new blog post. Then, map this type (e.g. using AutoMapper) to your BlogPost entity, and fill in the user ID as well.
To use built-in validation such as Model.IsValid(), put the data annotations attributes on the DTO instead.
Honestly, I would have the value assigned via the controller. If you had someone messing with your html via Firebug, they could actually change the id before it was passed and submitted to your form. I would remove it from your Create view and submit from the controller.
As per a question that I asked yesterday I was trying to find a way to dynamically create more text boxes and have those map to my view's model so upon post to the server it will grab all the dynamically(js) generated text boxes and post that to an object such as a List.
To give an example of this confusing question:
I have a textbox that is labeled "Primary Contact" and the ticket creator can enter the contacts name and phone number into this box. What I want to do essentially is, switch this to three text boxes. One for Name, Email and PhoneNumber instead of one box. Then I will create some javascript that will dynamically create three more boxes to add another contact to this List collection. Then when the user submits the form to modify or create the ticket it passes this collection inside the model to the controller. However with petapoco it is a little confusing. Let me show you the controller:
[HttpPost]
public ActionResult ModifyTicket(Ticket model)
{
string userString = User.Identity.Name.Replace("ONHOLD\\", "");
if (ModelState.IsValid)
{
model.CreatedDate = DateTime.Now;
model.LastUpdateBy = Util.GetEmployeeIdByName(userString);
model.LastUpdate = DateTime.Now;
model.IsComplete = false;
model.ClientString = Util.GetClientNameById(model.ClientId);
model.LocationString = Util.GetLocationNameById(model.LocationId);
model.Update();
SuccessMessage = "You have successfully updated ticket number: " + model.TicketId + " for the following client: " + model.ClientString + ".";
return RedirectToAction("Index");
}
ErrorMessage = "Woops! Something went wrong, please check back in a few moments, if the problem persists please contact development.";
return RedirectToAction("Index");
}
The simple answer to this would be that my database model would contain a List object for this exact reason. However, I am using PetaPoco and I'm not entirely sure how it would be done. I could manually add in a collection to my Database model but when I regenerate my model based on any database schema changes I will lose any changes I've made to the file.
I am also using a partial class that my view uses for validation using DataAnnotations. However this class is identical to the database model it just contains DataAnnotations to provide client-side validation.
If anyone understands what I'm trying to accomplish I would be more than happyto provide more information to clarify any missing pieces. I just need a resolution to this as I can't find a solid way to go about resolving this issue!
Not entirely sure what you mean but it's easy to model bind from/to a list with MVC as you may already know. As for saving a deep object like this I'd use the [Ignore] attribute on the Ticket.List so it isn't persisted and handle it separately. I'd load the Contacts in separately from the Ticket object then manually add them to the Ticket object, alternatively use a join query and try the one-to-many approach to load it all in one go.
I think you're expecting Petapoco to update all in one? This won't happen you'll need to break it up. Hard to say from what you've written so far. There won't be a long list of contacts (from the sounds of it) so just insert or update them one by one.
Well that might help, or might not.
Let me explain the whole context:
I'm using ASP.NET MVC 2, EF4 (POCO).
I trying to do a generic repository for my app.
I'm having problem on updating a many to many relationship.
I have an item that is related to other by a many to many table. In the View, the user picks the desired Categories, and send just the chosen id's to the Controller.
Then, the Controller queries the Category Repository, adding it to the main item:
item.Categories.Add(CategoriesRepository.Single(id);
But, when I go the Repository and try to save like this:
Entities.ApplyCurrentValues(entity);
Context.SaveChanges();
But, the state of my entity is Added.
Then, I Cannot save my entity :(.
How can I solve this problem?
Thanks for your answers.
I have in the View, the following code:
<%= Html.CheckBoxList("Categories", ((IEnumerable<Categories>)ViewData["Categories"]).ToDictionary(c => c.ID.ToString(), c => c.Name)
, Model.Categories.ToDictionary(c => c.ID.ToString(),c => c.Name )) %>
Where CheckBoxList is a HTMLHelper.
Im putting the ids as values in the View, because I dont know other way to put and then get this information from the View.
How can I use the ObjectStateManager.ChangeRelationshipState method?
Like this? :
itemRepository.Db.ObjectStateManager.ChangeRelationshipState(item, item.Categories, "Categories", System.Data.EntityState.Modified);
I trying in this way, but it returns error.
Help! lol
You've got a few problems.
1) ApplyCurrentValues only works for scalar-properties. Since your trying to add a Category to the Categories navigational property on Item, this will not work.
2) You say this:
the user picks the desired Categories, and send just the chosen id's to the Controller.
How can your Controller accept a bunch of id's? How is this model binding done? We need more info on how your View is bound to your model, what's being passed to the action method. But it sounds like you need to redesign this particular View with the help of a ViewModel.
3) Change tracking with POCO's in MVC is a royal pain in the butt. In your scenario, you'll need to use ObjectStateManager.ChangeRelationshipState to manually set the Categories relationship to **Modified.
Honesty though, it's more pain than it's worth. I went through this same problem.
Cop it on the chin - go grab the entity first and use Controller.UpdateModel:
[HttpPost]
public ActionResult Item(Item item)
{
// get the existing item
var existingItem = ItemRepository.Single(item.Id);
// use MVC to update the model, including navigational properties
UpdateModel(existingItem);
// save changes.
Context.SaveChanges();
}
I'm trying to design a solution in MVC in which a string representation of a class is passed to the controller which should then build a grid with all the data belonging to that class in the DB. (I'm using an ORM to map classes to tables).
//A method in the Model that populates the Item Property
foreach (MethodInfo method in sDRMethods)
{
if (method.Name.Contains(_domainTable))
{
Items = method.Invoke(repositoryObject, null);
break;
}
}
//View uses this Items property of the Model to populate the grid.
public object Items;
//_domainTable is the name of the table/class (in string format).
//repositoryObject is the object that has methods to return IEnumerable<class> collection object of each type.
The problem I have is that I do not know how to cast the "Items" property in my view to iterate through it and build a grid.
I have tried using the "http://mvcsharp.wordpress.com/2010/02/11/building-a-data-grid-in-asp-net-mvc/" but the generic extension method is expecting to know the specific type that it should work with.
I would prefer to use MVC but it looks like I cannot easily have this working(which is very hard to believe).
I really don't like the sound of what you are trying to do. Why convert the table to a string?
The only time you would convert to a string, is when the view gets rendered. And that, in most cases, should be left to the MVC framework.
The code you mentioned uses an HtmlTextWriter which is fine, because it will render straight to the response.
However, it sounds as if you are trying to reinvent the wheel by rendering everything to a string, rather than leaving that to the framework.
Note that in MVC the views are just templates for rendering strings, which is, if I have understood you, exactly what you need.
So, if I have remotely understood what you are trying to do, and it is a big if because your post is not clear, you should pass your class to view as part of the strongly typed model, and then write some basic design logic into the view.
If I am right, which is not certain, I think you have misunderstood how MVC works.
Have a look at a few examples of how to use views to render the data in a model. The model can be any class, it can be an IEnumerable, a list, whatever, and you can use foreach loops in the view to render out what you want, how you want it.
In this sense, MVC is very different to writing custom controls in plain vanilla ASP.NET.
Thanks for your reply awrigley.
The requirement is quite simple. I perhaps made it sound awfully complex in my post.
On an Index view, I have to populate a dropdownlist with all the tables of the application that are system lookup. The "Admin" of the app, selects an item from the dropdownlist which should show the contects of that table in a grid so that the admin can perform CRUD operations using that grid.
What I am trying to do is, pass the selected item (which is the name of the table) to the controller which in turn passes it to the ViewModel class. This class uses reflection to invoke (code shown in my original question) the right method of a repository which has got methods like:
public IEnumerable GetAllTable1Data()
{
.....
}
The problem I have is that when I invoke the method, it returns a type "object" which I cannot cast to anything specific because I don't know the specific type that it should be cast to. When this object is passed to the view, the grid is expecting an IEnumerable or IEnumerable but I do not know this information. I am not able to do this:
(IEnumerable)method.Invoke(repositoryObject, null)
I get: cannot cast IEnumerable to IEnumerable
I (kind of) have the grid now displaying but I am using a Switch statement in the view that goes:
Switch(SLU_Type)
{
case "SLU_Table1": Html.Grid((IEnumerable)Model.Items);
case "SLU_Table2": Html.Grid((IEnumerable)Model.Items);
.....
}
I don't like this at all, it feels wrong but I just cannot find a decent way!
I could have partial views for each of the system look up tables but for that I'll have to add around 30 partial views with almost exactly same code for the Action & View. This does not seem right either!
Hopefully, this gives you a better understanding of what I'm trying to achieve.