Is there any good reason to use FormCollection instead of ViewModel?

Question

I\'ve inherited a code base written in ASP.Net MVC 4. Every post method takes a FormCollection. Aside from annoyance of having to access the values through quot

Answer 1

There are always workarounds for getting away from a FormCollection lol.. you can have hidden fields bound to your view model variables in the form to your heart's content.

Form collections mostly emerge from the laziness of creating a view model but still end up taking time trying to get figure out how to get the values out of it in your controller :P

I think it was simply created in the very beginning of MVC as an alternative to using strongly typed views when having very simple forms - back in the days when everyone used ViewBag :) ... and once hey had it in there they couldn't just take it out as simple as that.

Maybe you can use it if you are absolutely sure your view will never have more than one form input? Probably still a bad idea though..

I cant find any recent articles talking about any advantages of form collections.. while strongly typed views are everywhere.

Answer 2

You can always add the form collection properties to your method signatures. They will automatically be populated by form values with corresponding keys.

Answer 3

There are type of SPA apps where you have no idea about your model (there is no ViewModel at all and views are created dynamically (for short ;))), so FormCollection is your only choice where you implement custom post validation having entire page input values... If your view has a knowledge about the model then, of course, you can use your concrete ViewModel object. That's easy ;)

Answer 4

With form collection you will be able to get all the values inside the form. There can be situations where you may need to pass some additional values from the form which may not be part of your view model.

Just take an example of passing 10 hidden values from the form. The form collection makes sense.

The only difficulty that you may face is type casting. All form collection items that you get will be string; you may need to type cast based on your requirement.

Also model state validation is another area where you may face a challenge.

Answer 5

Ok, I see the general consensus here is that it isn't liked. To offer another perspective, I've always liked using the formcollection passed into the controller on POST actions. It offers the use of the TryUpdateModel method from the controller which will map the collection to your strongly typed class. TryUpdateModel also has overloads that allow you to white list the properties of the model that you want to allow to be updated.

if (TryUpdateModel(viewModel, new string[] { "Name" }))
{
    //Do something
}

It still allows all the model binding you want, but helps to keep anything other than the "Name" property on my viewmodel from being updated.

You can see more about the TryUpdateModel method here:

http://msdn.microsoft.com/en-us/library/system.web.mvc.controller.tryupdatemodel(v=vs.108).aspx

Answer 6

Well with Forms Collection you will find a quick way to get the values of a form. Otherwise you have to create a class that mimics the Form Fields and people are sometime lazy to create custom classes for less important/rarely used Forms.

No there is no extra benefit (in fact limited) of forms collection over a custom class as action parameters and it should be avoided whenever possible.