I have a method inside a controller that creates ViewData. For example this one
private void CreateFKViewData(OSQDCOL osqdcol, OSADCOL osadcol, IList<OSADCOL> targetTBLcols)
{
...
ViewData[osadcol.ColName] = new SelectList(SelectListItems, "key", "value", SelectListItems.First().Key);
}
If that method is placed inside the controller everything works as expected. I want to move that method outside my controller and place it into a different class in my BLL layer. The problem is that ViewData is not accessible outside the scope of the controller.
Any ideas?
I'm assuming you're using ASP.NET MVC and C#. Not sure it's a great idea to spread around concerns that a controller would normally do into classes outside of the controller, but suffice to say that the reason for your issue is that ViewData is made available by the fact that your controller class inherits from Controller which in turn inherits from ControllerBase (which is where ViewData is provided). So let's say you wanted to call a method in another class from your controller, and you wanted that method to be able to manipulate ViewData. Consider the following:
public class TestController : Controller
{
// GET: Test
public ActionResult Index()
{
var externalclass = new SomeRandomClass(this);
externalclass.DoStuff();
return View();
}
}
public class SomeRandomClass
{
ControllerBase _callingController = null;
public SomeRandomClass(ControllerBase callingController)
{
this._callingController = callingController;
}
public void DoStuff()
{
this._callingController.ViewData["hello"] = "world";
}
}
Related
I have this controller
public class DownloadController : Controller
{
[HttpPost]
public FileContentResult GetFile(MyModel model)
{
// Action code
}
}
And this model
public class MyModel
{
public string Test { get; set; }
}
Passing model from the View to the controller works fine like this
#using (Html.BeginForm("GetFile", "Download", FormMethod.Post))
{
#Html.HiddenFor(m => m.Test)
<button type="submit" name="submit" class="submit">Download</button>
}
The model is correctly passed to the controller and I can do what I need to do with it.
Now, what I'm trying to achieve is to make this GetFile() controller action to be generic, so I can pass it any model, without strongly typing the model class in method signature, like I did in the example above.
I know I can achieve this by overriding GetFile() method once for each model that I have, but I'm wondering is there a better way to do this, to stay DRY as much as possible?
Thank you.
I'd suggest using a base class:
public class BaseGetFileModel {}
which various models will derive from.
[HttpPost]
public FileContentResult GetFile(BaseGetFileModel model)
EDIT:
OK, if you want a generic way of doing this, then you could do this:
[HttpPost]
public FileContentResult GetFile()
{
var someValue = Request["SomeValue"];
}
You don't accept any model parameter, you simply pick up POST'd values from the request. Or you could iterate through the request values collection, if you want to avoid hard-coding key names.
Why does T4MVC uses virtual for controller methods? Changing a
public ActionResult Details (string Id)
to:
public virtual ActionResult Details (string Id)
I have already seen other questions about T4MVC but didn't understand why.
Usually if a framework/library needs virtual methods (see also Nhibernate) it means somewhere/sometime your methods will be overridden.
So T4MVC marks your action methods as virtual because it's overrides them.
Lets take a simple controller:
public partial class HomeController : Controller
{
public virtual ActionResult Index()
{
ViewBag.Message = "Welcome to ASP.NET MVC!";
return View();
}
}
If you go to the generated HomeController.generated.cs under the T4MVC.tt you will find a generated class which inherits from your controller and overrides your action method:
[GeneratedCode("T4MVC", "2.0"), DebuggerNonUserCode]
public class T4MVC_HomeController: MvcApplication8.Controllers.HomeController {
public T4MVC_HomeController() : base(Dummy.Instance) { }
public override System.Web.Mvc.ActionResult Index() {
var callInfo = new T4MVC_ActionResult(Area, Name, ActionNames.Index);
return callInfo;
}
}
I haven't used T4MVC so I don't know why and for what purpose T4MVC creates this generated class.
The only benefit I can see for making them virtual is to allow the developer to 'Go to Implementation/Definition' where The T4MVC helpers are used. This works because the Controller's type on the static Helper 'MVC' is the base controller type.
public static partial class MVC
{
public static HomeController Home = new T4MVC_HomeController();
}
So in the following snippet, Go to Definition on the Action Name will go to Base Implementation:
#Url.Action(MVC.Home.Index())
+1 David Ebbo for such an intuitive feature. I was mind blown when I realized this!
PS: this does not work for the parameterless actions added via the partial function, instead they navigate to the generated code, unfortunately.
What is the best way to consume WebAPI service from ActionResult in another controller?
Basicaly i have a controller that returns the data.
public class MyApiController : ApiController
{
public MyData Get()
{
//returns the data
}
}
and i want to consume this data from
public class MyConsumeController: Controller
{
public ActionResult MyConsumeAction()
{
var something = //Call Get inside MyApiController
}
}
Any ideas?
Note: I know how to consume it using HttpClient (different project) or jquery (from views).
You could use the client API - the HttpClient class. And here's another sample.
When a view model is created you can populate the options (e.g. used in a dropdown list) into a setter property of the view model.
The problem is that when that view model is later passed as a parameter (by the framework!) into an action method, those property values has not become automagically
repopulated, so if you need to redisplay the form because of validation errors, you need to repopulate those options again.
One potential solution, which I am asking for specifically in this question, is how to make the MVC framework instantiate the view model with constructor injection, which would provide the view model constructor with an implementation of some kind of data access object (e.g. a repository) that can be used for retrieving the options when they are requested by the view (e.g. in the helper method "DropDownListFor") ?
I think the solution might have something to do with implementations of IModelBinderProvider or IModelBinder but after having experimented with these things from example code snippets here and there on the net, I am still looking for a completely working example, with downloadable executable code without any missing piece of how putting all things together.
If you are looking for some alternative discussion about how to populate a select list, e.g. with "Dependecy Lookup" instead of "Dependecy Injection" you may want to check out the following discussion:
Best way to populate SelectList for ViewModel on GET/POST
Best way to populate SelectList for ViewModel on GET/POST
Some days ago I wrote the following follow-up-question in that thread about the "Dependecy Injection" I am now looking for in this thread:
https://stackoverflow.com/a/8674525/310457
(which provides a code example about the problem I am looking for a solution of)
But instead of hoping that someone will find that old thread with a less specific title, I have created this new question with a more specific subject about what I am looking for.
And I will also provide a link from that thread into this new question for anyone that want to follow-up regarding this specific solution I am looking for.
I'm assuming you want to have your ViewModels automatically injected with something via their Constructor - for example some kind of configuration object that the View will use to determine what to show. I'm also assuming that this approach is causing a "No parameterless constructor defined for this object" error when MVC tries to automatically create and bind a model instance, from the arguments of your Controller Action. Let's also then assume that we will use a DI framework to inject the SiteConfig object into our Controllers automatically at runtime.
This means that the only problem we have to solve is how to get the injected object from our Controller into its Actions' ViewModels when they are automatically bound.
So let's define a base model for others to inherit from.
BaseViewModel
public class BaseViewModel
{
public ISiteConfig SiteConfig { get; set; }
public BaseViewModel(ISiteConfig siteConfig)
{
this.SiteConfig = siteConfig;
}
}
And now let's create a model that inherits from it.
IndexViewModel
public class IndexViewModel : BaseViewModel
{
public string SomeIndexProperty { get; set; }
public IndexViewModel (ISiteConfig siteConfig) : base(siteConfig) {}
}
And now let's define a Base Controller that our Controllers will inherit from.
BaseController
public abstract class BaseController : Controller
{
protected BaseController(ISiteConfig siteConfig)
{
_siteConfig = siteConfig;
}
private readonly ISiteConfig _siteConfig;
public ISiteConfig SiteConfig
{
get
{
return _siteConfig;
}
}
}
Now we define our actual controller.
HomeController
public HomeController: BaseController
{
public HomeController(ISiteConfig siteConfig): base(siteConfig) {}
}
Assuming we're using Ninject for DI, Ninject would be configured to automatically create the Controller and pass a concrete ISiteConfig object into its Constructor at runtime.
Now we add our Action to the Controller.
Index Action
public ActionResult Index(IndexViewModel model)
{
return View(model);
}
And so this is the point where without doing anything else, MVC will explode with a "Parameterless Constructor" error if you try to call the Index Action, because MVC can't find a ViewModel constructor that takes no arguments.
And so, the answer. We need to override the default ModelBinder.
BaseViewModelBinder
public class BaseViewModelBinder : DefaultModelBinder
{
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
if (modelType == typeof(BaseViewModel) || modelType.IsSubclassOf(typeof(BaseViewModel)))
{
var baseControl = controllerContext.Controller as BaseController;
if (baseControl == null)
{
throw new Exception("The Controller must derive from BaseController");
}
var instance = Activator.CreateInstance(modelType, baseControl.SiteConfig);
bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => instance, modelType);
return instance;
}
else
{
return base.CreateModel(controllerContext, bindingContext, modelType);
}
}
}
And we need to set this as the default model binder in global.asax.cs :
protected void Application_Start()
{
...
ModelBinders.Binders.DefaultBinder = new BaseViewModelBinder();
}
That's all. As you can see, when you view the Index Action now, MVC will use our custom model binder. It will realise that the IndexViewModel derives from BaseViewModel, and so will attempt to spin up an IndexViewModel instance using the ISiteConfig it can find in the Action's Controller (because the Controller derives from BaseController).
I have this IPageModel interface which is the base for all my models in my project.
The current model is a part of the RouteData and I want to inject this instance to my controllers.
this is how I do it today
x.For<IPageModel>().UseSpecial(y => y.ConstructedBy( r => ((MvcHandler) HttpContext.Current.Handler).RequestContext.RouteData.GetCurrentModel<IPageModel>()));
Is it possible to tell structuremap to inject the correct type instead of the IPageModel?
An couple examples would be like this:
public HomeController(Home model) {
// Home implements IPageModel
}
and
public PageController(Page model) {
// Page implements IPageModel
}
The RouteData object has the correct instance of the model
You can make your controllers generic, so they work with a specific type of IPageModel.
so you would have
HomeController<Home> and
PageController<Page>
If you make them derive from a single base class which only has a constructor with 1 parameter (an instance of T) so:
public abstract class BaseController<T> where T : IPageModel
{
protected T Model { get; private set; }
public BaseController(T model)
{
Model = model;
}
This way you will get a controller with a newly constructed instance of (for example) Home. I don't think you want an empty model but you'll have to handle this in your registrations in structuremap by scoping them on the session or request for example.