I'm writing an MVC2 app using DataAnnotations. I have a following Model:
public class FooModel
{
[ScaffoldColumn("false")]
public long FooId { get; set; }
[UIHint("BarTemplate")]
public DateTime? Bar { get; set;}
}
I want to create a custom display template for Bar. I have created following template:
<%# Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<DateTime?>" %>
<div class="display-label">
<span><%: Html.LabelForModel() %></span>
</div>
<div class="display-field">
<span><%: Html.DisplayForModel()%></span>
<%: Html.ActionLink("Some link", "Action", new { id = ??FooId?? }) %>
</div>
Now, my problem is that inside template for Bar I want to access another property from my model. I don't want to create a separate template for FooModel because than I will have to hardcode all other FooModel properties.
After a brief investigation with a debugger I can see that:
this.ViewData.ModelMetadata.ContainerType
is FooModel (as expected)
this.ViewData.TemplateInfo has a
non-public property VisitedObjects
(of type
System.Collections.Generic.HashSet<object>)
which contains two elements:
FooModel and DateTime?.
How can I get access to my FooModel? I don't want to hack my way around using Reflection.
Update:
I've accepted mootinator's answer as it looks to me as the best solution that allows type-safety. I've also upvoted Tx3's answer, as mootinator's answer builds upon it. Nevertheless, I think that there should be a better support form MVC in those kind of scenarios, which I believe are quite common in real world but missing from sample apps.
Maybe you could create new class, let's say UserDateTime and it would contain nullable DateTime and rest of the information you need. Then you would use custom display template for UserDateTime and get access to information you require.
I realize that you might be looking for other kind of solution.
I think you may be better off extracting this functionality to an HtmlHelper call from the Parent View.
Something like RenderSpecialDateTime<TModel>(this HtmlHelper html, Expression<Func<TModel,DateTime?>> getPropertyExpression) would probably do the job.
Otherwise, you will have to do something like what Tx3 suggested. I upvoted his answer, but posted this as an alternative.
Couldn't you use the ViewData dictionary object in the controller and then grab that in the ViewUserControl? It wouldn't be strongly typed but...you could write a helper to do nothing if it's empty, and link to say the example login history page if it had a value.
It would appear that somewhere between MVC 5.0 and 5.2.2 a "Container" property was added on to the ModelMetadata class.
However, because all of the methods in a provider responsible for metadata creation (GetMetadataForProperty, Create etc) do not have container in their signature, the Container property is assigned only in certain cases (GetMetadataForProperties and GetMetadataFromProvider according to reflected code) and in my case was usually null.
So what I ended up doing is overriding the GetMetadataForProperty in a new metadata provider and setting it there:
public override ModelMetadata GetMetadataForProperty(Func<object> modelAccessor, Type containerType, string propertyName)
{
var propMetaData = base.GetMetadataForProperty(modelAccessor, containerType, propertyName);
Object container = modelAccessor.Target.GetType().GetField("container").GetValue(modelAccessor.Target);
propMetaData.Container = container;
return propMetaData;
}
I know this is reflection but it's fairly succinct. It would appear that MS is correcting this oversite so maybe it will be possible to replace the reflection code in the future.
Sorry if this suggestion seems daft, I haven't tried it, but couldn't you do what Tx3 suggested without having to create a bunch of new classes by defining a generic class to reference whatever type of parent you want?
public class FooModel
{
[ScaffoldColumn("false")]
public long FooId { get; set; }
[UIHint("BarTemplate")]
public ParentedDateTime<FooModel> Bar { get; set;}
public FooModel()
{
Bar = new ParentedDateTime<FooModel>(this);
}
}
public class ParentedDateTime<T>
{
public T Parent {get; set;}
public DateTime? Babar {get; set; }
public ParentedDateTime(T parent)
{
Parent = parent;
}
}
You could expand that to encapsulate any old type with a <Parent, Child> typed generic, even.
That would also give you the benefit that your strongly typed template would be for
Inherits="System.Web.Mvc.ViewUserControl<ParentedDateTime<FooType>> thus you would not have to explicity name which template to use anywhere. This is more how things are intended to work.
Related
I'm developing an MVC3 application and I have a page (well, a view) that let the users edit document's metainfo (a classic #Html.BeginForm usage). For general documents users will see standard fields to fill up, but through a dropdownlist they will be able to specify the type of the document: this, through an ajax call, will load new fields on the edit-document-form.
Whem the user submit the completed form, at last, the controller should read all the standard fields, plus all the fields loaded as being specific to the type of document selected.
Question is, how can I handle all this extra fields in a controller?
Say that I have Document class and a bunch of other classes extendinf Document, like Contract : Document, Invoice : Document, Complaint : Document and so forth, each having specific property (and this fields loaded on the form), how do I write the action in the controller?
I thought to use something like (I'll omitt all the conversions, validations, etc, for brevity)
[HttpPost]
public ActionResult Save(dynamic doc)
{
int docType = doc.type;
switch (docType)
{
case 1:
var invoice = new Invoice(doc);
invoice.amount = Request.Form["amount_field"];
invoice.code = Request.Form["code_field"];
//and so forth for every specific property of Invoice
Repository.Save(invoice);
break;
case 2:
var contract = new Contract(doc);
contract.fromDate = Request.Form["fromDate_field"];
contract.toDate = Request.Form["toDate_field"];
//and so forth for every specific property of Contract
Repository.Save(contract);
break;
..... // and so forth for any document types
default:
break;
}
}
But it seems a very dirty approach to me. Do you have a better idea on how to achive this? Maybe there's a pattern that I don't know nothing about to approach this kind of scenario.
Update
A second idea comes to my mind. After commenting Rob Kent's answer, I thought I could take a different approach, having just one class Document with a property like
public IEnumerable<Field> Tipologie { get; set; }
where
public class Field
{
public int IdField { get; set; }
public String Label { get; set; }
public String Value { get; set; }
public FieldType ValueType { get; set; }
public List<String> PossibleValues { get; set; } // needed for ENUMERATION type
}
public enum FieldType
{
STRING, INT, DECIMAL, DATE, ENUMERATION
}
Is this a better approach? In this case I can have just an action method like
[HttpPost]
public ActionResult Save(Document doc)
But shoud I create the fields in the view in order to make the MVC engine do the binding back to the model?
Given that the class inheriting from Document in the first approach will probably be generated at run-time, would you prefer this second approach?
To keep it all hard-typed on the server, you could use an abstract base type with a custom binder. See my answer here to see how this works: MVC generic ViewModel
The idea is that every time they load a new set of fields, you change the BindingType form variable to the instantiated type of the handler. The custom binder is responsible for creating the correct type on submission and you can then evaluate that in your action, eg:
if (model is Contract) ...
I'm not sure if you will be able to set up different actions each with a different signature, eg,:
public ActionResult Save(Contract contract) ...
public ActionResult Save(Invoice invoice) ...
Pretty sure that won't work because Mvc will have already decided which method to call, or maybe it will firstly see what type it gets back and then decides.
In my linked example, I am checking for overridden base members but if that is not an issue for you, you just need to create the correct type.
Questions
There are actually two related questions:
Should I create a ViewModel for each page?
If you do not have problems in creating a single ViewModel class for the two pages (Create.cshtml and Edit.cshtml) how can I validate the ViewModel in different ways (depending on the page that is being used)
Source
ViewModel
public class ProjectViewModel
{
public string Name { get; set; }
public string Url { get; set; }
public string Description { get; set; }
}
Edit.cshtml
#using BindSolution.ViewModel.Project
#model ProjectViewModel
#{
ViewBag.Title = Model.Name;
}
#Html.EditorForModel()
Create.cshtml
#using BindSolution.ViewModel.Project
#model ProjectViewModel
#{
ViewBag.Title = "New Project";
}
#Html.EditorForModel()
ProjectValidator.cs
public class ProjectValidator : AbstractValidator<ProjectViewModel>
{
private readonly IProjectService _projectService;
public ProjectValidator(IProjectService projectService)
{
_projectService = projectService;
RuleFor(p => p.Name)
.NotEmpty().WithMessage("required field")
/*The validation should be made only if the page is Create.cshtml. That is, if you are creating a new project.*/
.When(p => p.??) //Problem Here!!
.Must(n => !_projectService.Exist(n)).WithMessage("name already exists");
RuleFor(p => p.Url)
.NotEmpty().WithMessage("required field");
}
}
Note that if the user is editing an existing project, validation of the property name should not be done again.
ProjectController.cs > Edit method
[HttpPost]
public ActionResult Edit(Guid projectID, ProjectViewModel model)
{
var project = _projectService.Repository.Get(projectID);
if (ModelState.IsValid && TryUpdateModel(project))
{
_projectService.Repository.Attach(project);
if (_projectImageWrap.Create(project) && _projectService.Repository.Save() > 0)
return AjaxRedirect("Index");
}
return View(model);
}
Notes
If I create a ViewModel for each page, there is a duplication of code since pages have the same properties.
Add a property on the ViewModel indicating what page it is being displayed does not solve my problem as to instantiate the ViewModel, I use AutoMapper.
To validate the data, I use FluentValidator.
Thank you all for your help!
My understanding is that there isn't a 1:1 correlation between ViewModels and Views. Oftentimes you will have a View that will not require a ViewModel to go alongside with it.
You will want to create a ViewModel if and only if you need a Model absolutely paralleled and tailored to a specific View. This will not be the case 100% of the time.
When the functionality / use case /validation is different between the pages I use different models. If its the exact same besides the presence of an ID or something similar I use the same model, and its also possible to just use the same view if the differences are pretty minor.
Since your validation is different, if I were doing it I would create two different models so that I could use the out of the box DataAnnotations, with your validation though it may not be required. You could also on the edit model have a readonly property for name since its not editable any longer.
For me the same object must have the same validation on every time, in main to ensure the consistence of the object, independently if it was created or edited.
i think that you should create only one validation, and edit your "exists" method to pass to verify if it is a new object or the current object in repository.
Personally, I don't have a problem with 2 view models, especially if (as Paul Tyng suggested) you use a base class for the fields that are common to edit and create scenarios.
However, if you really only want a single view model then you would either need to:
add a flag to the view model and use the When() method in your validator. Note though that this will not generate the appropriate client-side only validation
define a second validator and invoke the appropriate one from the controller (i.e. instead of the "automatic" validation)
Provide another view Edit.cshtml which will allow the user to edit the data for a selected item.
Create another view Query.cshtml which based on the ItemName will allow the users to query the Inventory table.
Perform the calculation for the total profit (numbersold times (saleprice-purchasecost). Display the total profit.
(BONUS) Create another view Sell.cshtml that will indicate the sale of an item. Adding one to NumberSold and subtract one from NumberInventory for the selected record.
I'm using MVC3 with Razor views and would like to build reusable DropDownLists for several of my classes, but after much searching I have not found an example that performs exactly how I need it...
For this example I have two classes like this:-
public class Person
{
public int ID { get; set; }
public string Name { get; set; }
public Group Group { get; set; }
}
public class Group
{
public int ID { get; set; }
public string Name { get; set; }
}
I have a working Controller/View for Person. The view has a DropDownListFor control:
#model Person
...
#Html.DropDownListFor(o => o.Group.ID, (ViewData["groups"] as SelectList))
The view uses the Person class directly, not an intermediary model, as I haven't found a compelling reason to abstract one from the other at this stage.
The above works fine... in the controller I grab the value from Group.ID in the Person returned from the view, look it up, and set Person.Group to the result. Works, but not ideal.
I've found a binder here: MVC DropDownList values posted to model aren't bound that will work this out for me, but I haven't got that working yet... as it only really seems useful if I can reuse.
What I'd like to do is have something like this in a template:-
#model Group
#Html.DropDownListFor(o => o.Group.ID, (ViewData["groups"] as SelectList))
And use it in a view like this:-
#Html.EditorFor(o => o.Group)
However the above doesn't seem to work... the above EditorFor line inserts editors for the whole class (e.g. a textbox for Group.Description as well)... instead of inserting a DropDownList with my groups listed
I have the above template in a file called Group.cshtml under Views/Shared/EditorTemplates
If this worked, then whenever a class has a property of type Group, this DropDownList editor would be used by default (or at least if specified by some attribute)
Thanks in advance for any advice provided...
You can create a drop down list user control to handle this. Under your Shared folder create a folder called EditorTemplates and place your user control there. MVC, by convention, looks in the Shared/EditorTemplates for any editor templates. You can override where it looks for the editor templates but I won't go in to that here.
Once you have your user control created, you'll need to decorate the appropriate property with the "UIHint" attribute to tell the engine what editor it should use for that property.
Following would be a sample implementation.
In the Shared/EditorTemplates folder your user control (_GroupsDropDown.cshtml in this case) would look like:
#model Group
#Html.DropDownListFor(o => o.ID, (ViewData["groups"] as SelectList))
Modify the Group property in the Person to add the UIHint attribute as follows:
**[UIHint("_GroupsDropDown")]**
public Group Group { get; set; }
In your controller you would need
ViewData["groups"] = new SelectList(<YourGroupList>, "ID", "Name");
Once you have the above code you can use the EditorFor syntax like you desire.
Hope this helps.
I hope I'm not missing something incredibly obvious here but is there any reason why model binder is always having trouble binding a view model that inherits from a collection?
Lets say I want to show a paged list and display a combo box and add button above it (dealing with simple lists). Involved classes would look like:
public class PagedList<T> : List<T>
{
public int TotalCount { get; set; }
}
And then a view model that looks like:
public class MyViewModel : PagedList<ConcreteModel>
{
public IEnumerable<ChildModel> List { get; set; }
public int? SelectedChildModelId { get; set; }
}
So in the view (Razor):
#model MyViewModel
#using (Html.BeginForm())
{
#Html.DropDownListFor(model => model.SelectedChildModelId, new SelectList(Model.List, "ChildModelId", "DisplayName"))
}
And the controller HttpPost action:
public ActionResult(MyViewModel viewModel)
{
...
}
The above will cause viewModel in ActionResult to be null. Is there a logical explanation for it? From what I can tell it's specific only to view models that inherit from collections.
I know I can get around it with custom binder but the properties involved are primitive types and there isn't even any generics or inheritance.
I've reworked the view models to have the collection inherited type as properties and that fixes the issue. However I'm still scratching my head over why the binder breaks down on it. Any constructive thoughts appreciated.
To answer my own question: All my models that have anything to do with collections no longer inherit from generic list or similar but instead have a property of the required collection type. This works much better because when rendering you can use
#Html.EditorFor(m => m.CollectionProperty)
And create a custom editor under Views/Shared/EditorTemplates for contained type. It also works beautifully with model binder since all individual items from collection get a index and the binder is able to auto bind it when submitted.
Lesson learned: if you plan to use models in views, don't inherit from collection types.
Sometimes model binding to a collection works better if the data in the form post is formatted differently.
I use a plugin called postify.
http://www.nickriggs.com/posts/post-complex-javascript-objects-to-asp-net-mvc-controllers/
Although I love what I'm learning, I'm finding it a struggle and need some help
I've been using these two tutorials which I think are awesome:
http://weblogs.asp.net/scottgu/archive/2010/07/16/code-first-development-with-entity-framework-4.aspx
http://msdn.microsoft.com/en-us/data/gg685467
Currently my main problem/confusion is:
I have a CodeFirst table/entity I don't know how to correctly get data from other tables/entities to show in my views:
public class Car {
public int ID { get; set; }
public string Name { get; set; }
public int EngineID { get; set; }
public virtual Engine { get; set; }
}
public class Engine {
public int ID { get; set; }
public string Name { get; set; }
public string Manufacturer { get; set; }
// (plus a whole lot of other things)
}
Now when I create a View for Cars (using the List type/option) I get a nice autogenerated list
#foreach (var item in Model) {
<tr>
<td>#item.ID</td>
<td>#item.Name</td>
<td>#item.EngineID</td>
</tr>
Perfect... except EngineID is mostly worthless to the viewer, and I want to show Engine.Name instead
So I assumed I could use EF lazy loading:
<td>#item.Engine.Name</td>
Unfortunately when I tried that, it says my ObjectContext has been disposed so can't get any further data requiring a connection
Then I tried going to the controller and including the Engine.Name
var cars = (from c in db.Cars.Include("Engine.Name") select c;
Which tells me: Entities.Engine does not declare a navigation property with the name 'Name'
... ? Lies
Include("Engine") works fine, but all I want is the Name, and Include("Engine") is loading a large amount of things I don't want
Previously in a situation like this I have created a view in the DB for Car that includes EngineName as well. But with CodeFirst and my noobness I haven't found a way to do this
How should I be resolving this issue?
I thought perhaps I could create a Model pretty much identical to the Car entity, but add Engine.Name to it. This would be nice as I could then reuse it in multiple places, but I am at a loss on how to populate it etc
Wanting to learn TDD as well but the above is already frustrating me :p
Ps any other tutorial links or handy things to read will be greatly appreciated
It isn't lies as you are actually trying to include a property that's a 2nd level down withouth giving it a way to navigate. If you let EF generate your DB with this structure, it would likely have made a navigation table called something like Car_Engine and if you include the name without the object it HAS mapped, then it's not got a navigation property in your new object.
The simple way around this is to go:
(from c in db.Cars.Include("Engine") select new { c, EngineName = c.Engine.Name }
If you still get navigation property errors then you might need to make sure your are mapping to your schema correctly. This can be done with EntityTypeConfiguration classes using the fluent API - very powerful.
This of course won't help in strongly typing your car object to show in MVC.
If you'd like to get around this, your gut feeling is right. It's pretty common to use viewmodels that are read only (by design, not necessarily set to readonly) classes that provide simple views of your data.
Personally I keep my model quite clean and then have another project with viewmodels and a presentation project to populate. I'd avoid using overlapping entities in your core model as it might lead to unpredictable behaviour in the data context and at least a peristance nightmare when updating multiple entities (ie who's responsible for updating the engine name?).
Using you viewmodels, you can have a class called CarSummaryView or something with only the data you want on it. This also solves the issue of being vulnerable to overposting or underposting on your site. It can be populated by the above query quite easily.
PS There's a bunch of advantages to using viewmodels beyond just not loading full heirarchies. One of the biggest is the intrinsic benefit it gives you with avoiding over and underposting scenarios.
There's loads of ways to implement viewmodels, but as a simple CarView example:
public class CarView
{
public int ID { get; set; }
public string Name { get; set; }
public string EngineName { get; set; }
}
This should be clearly seperated from your entity model. In a big project, you'd have a single viewmodels project that the presenter can return, but in a smaller one you just need them in the same layer as the service code.
To populate it directly from the query, you can do the following
List<CarView> cars = (from c in db.Cars.Include("Engine.Name") select new CarView() { ID = c.ID, Name = c.Name, EngineName = c.Engine.Name }).ToList();