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Model Binding vs Form Collection, performance, scalability, change, etc.? [duplicate]

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 quoted strings, it also leads to drawbacks such as not being able to use things like ModelState.IsValid, or [AllowHtml] attributes on my ViewModel properties. They actually did create ViewModel classes for each of their views, (though they are pretty much just direct wrappers around the actual Entity Framework Model classes), but they are only used for the GET methods.
Is there anything I'm missing about FormCollection that gives a reason why this may have actually been a good idea? It seems to only have drawbacks. I'd like to go through and "fix" it by using ViewModels instead. This would take a good bit of work because the ViewModels have properties that are interfaces and not concrete classes, which means either writing a custom binder or changing the ViewModels.
But perhaps there's something I'm missing where it makes sense to use FormCollection?

Is there any good reason to use FormCollection instead of ViewModel?
No. I have following issues.
Issue - 1
In case FormCollection is being used...It will be mandatory to Type Cast the Primitive Type Values un-necessarily because while getting the entry of specific Index of the System.Collections.Specialized.NameValueCollection, value being returned is of type String. This situation will not come in case of Strongly Typed View-Models.
Issue - 2
When you submit the form and goes to Post Action Method, and View-Model as Parameter exists in the Action method, you have the provision to send back the Posted Values to you View. Otherwise, write the code again to send back via TempData/ViewData/ViewBag
View-Models are normal classes, created to bind data to-from Views
Issue - 3
We have Data Annotations that can be implemented in View Model or Custom Validations.
ASP.Net MVC simplifies model validatons using Data Annotation. Data Annotations are attributes thyat are applied over properties. We can create custom validation Attribute by inheriting the built-in Validation Attribute class.
Issue - 4
Example you have the following HTML
<input type="text" name="textBox1" value="harsha" customAttr1 = "MyValue" />
Question : How can we access the value of customAttr1 from the above eg from inside the controller
Answer : When a form get posted only the name and value of elements are posted back to the server.
Alternatives : Use a bit of jQuery to get the custom attribute values, and post that along with the form values to action method
Another option is to rather put what you got in your custom attributes in hidden controls
That's the reason, I would always prefer to use View-Models

The only advantage I can think of is if you want to use the automatically generated controller provided when you don't specify a EF model to be strongly typed to. In that case, your Create and Edit actions will use the FormCollection object as it is a reliable, pre-existing artifact of the framework to work with for this purpose. Perhaps the previous developer chose this option while creating his controllers, and stuck with it since Visual Studio must know what it's doing :)
But, in reality, I would never recommend this headstart of a few seconds. It's always better to build out viewmodels, I would recommend looking at the effort to move in that direction if only for maintenance purposes. With model binding and strongly typed views and html helpers, you are much more likely to reduce the number of run-time errors as a result of changing some magic string and not realizing it until your page blows up.

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

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.

Yes. Sometimes, it can be useful. Here's an example:
Let's say we have in our db "date_and_time_field".
In Razor View, we want to use two form fields. The first one "Date" (maybe with jQuery UI Datepicker). The second one "Hour".
In the Controller Action, we compose the "date_and_time_field" by means of Request.Form["Date"] and Request.Form["Hour"].
There are other scenarios where it can be useful:
A cross-table (with checkBoxes in Razor view)
The collection Request.Unvalidated().Form (maybe this is not part of your question: I don't wanna be off-topic)

The default model binder will do almost everything you need it to do. I resorted to the FormCollection once - only to later figure out how to bind arrays of elements into a collection on the ViewModel.
Just go ViewModel. Better all around, for every reason enumerated.

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.

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

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.

Responding to the title question: yes.
There are some situations that FormCollection needs to be used. For instance, suppose a ViewModel that has a property that implements the 1 to N relation (in concrete case, a TimesheetViewModel with ICollection<TimesheetEntryViewModel>), and the Controller has to perform a validation between the time entries to not get a time collision between the end time of an entry and the start time of the following entry. To mark a related entry with a validation error, how can be the line index be retrieved?
Well, with the default model binding, the index value is lost in the Controller logic. Fortunately, FormController stores the index you used in the View and a more specific validation can be done.

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 ;)

C# Generic Data Abstraction

So essentially I'm making a WPF/MVVM Light application and I currently have a TreeView that represents a variety of different types of objects. Each of these objects is wrapped in a very generic "ViewModel" that currently just exposes their name to the TreeView display in the application.
Linked conceptually to this tree, I want to provide an Object Viewer below the tree, such that when a user selects an item in the three, the object viewer is populated with the Properties of that node and it allows the user to change and save new values to the node in question.
I'm effectively trying to create an abstraction that can take a variety of types (7 different object types) and expose their Properties AND allow the user to edit them. Essentially, I can bind the properties of this abstraction to a group of Text/Display boxes on the UI, and when the user hits save, have it call update methods on the actual underlying data objects from this middle wrapper class.
Currently, the only way I can think to accomplish this is to make a separate wrapper for each underlying object type (since they all have different Properties), and essentially hard-code the fields and update methods.
Are there any other options in terms of providing further abstraction and creating a general wrapper class capable of exposing and updating Properties from a variety of objects? Thanks.

Instead of wrapping every model in a different ViewModel, you may want to expose the model directly to the View and create a DataTemplate for each type of model, this will allow you to have different UIs for each model type without having to place an intermediate ViewModel in between. Just a suggestion.

How to avoid a databinding / events hell on a complex screen?

This is more of an architecture / design question.
I have run into a few projects in the past written in WPF/Windows Forms, etc. that have complex screens with a lot of fields and these fields are connected to each other (their values depend on each other with some logic involved).
These projects I have taken on after they were implemented, and I found a lot of events / data bind hell - what I mean by this is that because all these fields are depending on others they have implemented INotifyPropertyChanged and other fields are being modified as a result. This causes the same fields being updated 5-6 times when the screen loads and the order in which fields are populated causes horrible bugs. (For example, Date was set before Job Type, instead of after Job Type, so I end up with a different Job Fee.)
To make matters worse, some hacks are implemented on UI events (for example, DropDown changed to update field X) while others are in the domain model that the UI binds to.
Basically, it's a huge mess, and I just want to know what the best way to implement something like this is if I was to start from scratch. Or is it a good idea to avoid such a complex screen in the first place?

I would try to keep the business logic out of the property setters as much as possible.
First of all, if several properties are needed for one calculation, I'd write one method that does the calculation, and call that method when appropriate. E.g. if all different combinations of property values make sense, one could just call the method in the setters of each property, making sure that the same code runs any time one of the properties is changed. If you only can evaluate special combinations of property values, you could either implement a command and let the user decide when to calculate the resulting changes, or you could provide feedback through validation, and only evaluate the property changes if the combination is valid. If there are several interdependent properties, I often use a "ChangeInitiator" variable to indicate what property has changed, so that it is clear in the calculation method which property is responsible for the change and which others should change as a result. Basically, this is the same as doing one part of the calculation in each property setter, but I find that it helps me to keep an overview of things if the different parts of the relationship are all in one method.
In a program I wrote once, I had some calculations running on a background thread periodically, so I would just set a flag whenever a piece of data changed that required a new calculation, and do all the updates based on a timer every second or so... that could also help you get the logic more straight, and it avoids to have the calculation run several times for one set of related changes.
With regard to change notification, I'd really try to only use it for UI data binding.

We have fairly complex UIs (including several related fields of different types in, say for example a Row in a DataGrid) and the MVVM pattern has worked pretty well for us. All the properties coming from the Model and exposed to the View that have complex logic related are "wrapped" by an equivalent property in the ViewModel, which has no Backing Field, but rather points directly to the Model:
public class SomeComplexViewModel
{
public SomeModel Model {get;set;}
public string SomeCrazyProperty
{
get
{
return Model.SomeCrazyProperty;
}
{
Model.SomeCrazyProperty = value;
//... Some crazy logic here, potentially modifying some other properties as well.
}
}
}
<TextBox Text="{Binding SomeCrazyProperty}"/>
This removes the "initial value" problem, as the initial value read by the Binding is actually the real value coming from the Model, and thus the logic placed in the Setter is executed only when needed.
Then, for dummy properties (which have no logic behind), we bind directly from the View to the Model:
<TextBox Text="{Binding Model.SomeRegularProperty}"/>
This reduces the bloat in the ViewModel.
With regard to events in the code behind, I totally avoid that. My code behind files are almost always one InitializeComponent() and nothing else.
Only View-Specific logic is placed in the code behind (such as animations stuff, etc), when it cannot be directly done in XAML, or is easier to do in code (which is not the case most of the time).
Edit:
It's important to mention that the winforms binding capabilities are a joke compared to the XAML-based ones. could that be the cause you're seeing those horrible messes in those projects?

Dynamic form with no real OOP or objects?

I am tacking a large refactor of a project, and I had asked this question to confirm/understand the direction I should go in and I think I got the answer that I wanted, which is not to throw away years worth of code. So, now begins the challenge of refactoring the code. I've been reading Martine Fowler and Martin Feathers' books, and they have a lot of insight, but I am looking for advice on the ultimate goal of where I want the application to be.
So to reiterate the application a little bit, its a dynamic forms system, with lots of validation logic and data logic between the fields. The main record that gets inserted is the set of form fields that is on the page. Another part of it is 'Actions' that you can do for a person. These 'Actions' can differ client by client, and there are hundreds of 'Actions'. There is also talk that we can somehow make an engine that can eventually take on other similar areas, where a 'person' can be something else (such as student, or employee). So I want to build something very de-coupled. We have one codebase, but different DBs for different clients. The set of form fields on the page are dynamic, but the DB is not - it is translated into the specific DB table via stored procs. So, the generic set of fields are sent to the stored proc and the stored proc then decides what to do with the fields (figure out which table it needs to go to). These tables in fact are pretty static, meaning that they are not really dynamic, and there is a certain structure to it.
What I'm struggling specifically is how to setup a good way to do the dynamic form control page. It seems majority of the logic will be in code on the UI/aspx.cs page, because its loading controls onto the webpage. Is there some way I can do this, so it is done in a streamlined fashion, so the aspx.cs page isn't 5000 lines long? I have a 'FORM' object, and one of the properties is its' 'FIELDS'. So this object is loaded up in the business layer and the Data layer, but now on the fron end, it has to loop through the FIELDS and output the controls onto the page. Also, someway to be able to control the placement would be useful, too - not sure how do get that into this model....
Also, from another point of view - how can I 'really' get this into an object-oriented-structure? Because technically, they can create forms of anything. And those form fields can represent any object. So, for example, today they can create a set of form fields, that represent a 'person' - tomorrow they can create a set of form fields that represent a 'furniture'. How can I possibly translate this to to a person or a furniture object (or should I even be trying to?). And I don't really have controls over the form fields, because they can create whatever....
Any thought process would be really helpful - thanks!

How can I possibly translate this to to a person or a furniture object
(or should I even be trying to?)
If I understand you correctly, you probably shouldn't try to convert these fields to specific objects since the nature of your application is so dynamic. If the stored procedures are capable of figuring out which combination of fields belongs to which tables, then great.
If you can change the DB schema, I would suggest coming up with something much more dynamic. Rather than have a single table for each type of dynamic object, I would create the following schema:
Object {
ID
Name
... (clientID, etc.) ...
}
Property {
ID
ObjectID
Name
DBType (int, string, object-id, etc.)
FormType ( textbox, checkbox, etc.)
[FormValidationRegex] <== optional, could be used by field controls
Value
}
If you can't change the database schema, you can still apply the following to the old system using the stored procedures and fixed tables:
Then when you read in a specific object from the database, you can loop through each of the properties and get the form type and simple add the appropriate generic form type to the page:
foreach(Property p in Object.Properties)
{
switch(p.FormType)
{
case FormType.CheckBox:
PageForm.AddField(new CheckboxFormField(p.Name, p.Value));
break;
case FormType.Email:
PageForm.AddField(new EmailFormField(p.Name, p.Value));
break;
case FormType.etc:
...
break;
}
}
Of course, I threw in a PageForm object, as well as CheckboxFormField and EmailFormField objects. The PageForm object could simply be a placeholder, and the CheckboxFormField and EmailFormField could be UserControls or ServerControls.
I would not recommend trying to control placement. Just list off each field one by one vertically. This is becoming more and more popular anyway, even with static forms who's layout can be controlled completely. Most signup forms, for example, follow this convention.
I hope that helps. If I understood your question wrong, or if you'd like further explanations, let me know.

Not sure I understand the question. But there's two toolboxes suitable for writing generic code. It's generics, and it's reflection - typically in combination.
I don't think I really understand what you're trying to do, but a method using relfection to identify all the properties of an object might look like this:
using System.Reflection;
(...)
public void VisitProperties(object subject)
{
Type subjectType = subject.GetType();
foreach (PropertyInfo info in subjectType.GetProperties()
{
object value = info.GetValue(subject, null);
Console.WriteLine("The name of the property is " + info.Name);
Console.WriteLine("The value is " + value.ToString());
}
}
You can also check out an entry on my blog where I discuss using attributes on objects in conjunction with reflection. It's actually discussing how this can be utilized to write generic UI. Not exactly what you want, but at least the same principles could be used.
http://codepatrol.wordpress.com/2011/08/19/129/
This means that you could create your own custom attributes, or use those that already exists within the .NET framework already, to describe your types. Attributes to specify rules for validation, field label, even field placement could be used.
public class Person
{
[FieldLabel("First name")]
[ValidationRules(Rules.NotEmpty | Rules.OnlyCharacters)]
[FormColumn(1)]
[FormRow(1)]
public string FirstName{get;set;}
[FieldLabel("Last name")]
[ValidationRules(Rules.NotEmpty | Rules.OnlyCharacters)]
[FormColumn(2)]
[FormRow(1)]
public string LastName{get;set;}
}
Then you'd use the method described in my blog to identify these attributes and take the apropriate action - e.g. placing them in the proper row, giving the correct label, and so forth. I won't propose how to solve these things, but at least reflection is a great and simple tool to get descriptive information about an unknown type.

I found xml invaluable for this same situation. You can build an object graph in your code to represent the form easily enough. This object graph can again be loaded/saved from a db easily.
You can turn your object graph into xml & use xslt to generate the html for display. You now also have the benefit of customising this transform for differnetn clients/versions/etc. I also store the xml in the database for performance & to give me a publish function.
You need some specific code to deal with the incoming data, as you're going to be accessing the raw request post. You need to validate the incoming data against what you think you was shown. That stops people spoofing/meddling with your forms.
I hope that all makes sense.

3 layer architechture and little details like dropdown lists

So I am refactoring a little application as an example to get more practice. The purpose of the application (let's say) is to collect the data from a "sign up new user" form, save it in the database. The only limitation I have is I have to use a special custom Data Access class which communicates directly with the database and returns the data (if applicable) in a DataTable object.
I have a question regarding a little details on a form and how do they fit in into the layer architecture. For example, my form has a drop down list that's fed from the database, but at the same time drop down list doesn't represent an object per SE (unlike a User that is a object, there is a class User that has multiple methods, data members etc). I don't want to have calls to the stored procedure right there in the code behind but I also do not wish to overdo on abstraction.
What would be an elegant way to take care of these little details w/o creating a class abstraction galore.
Hope I am being clear

Funny you should ask that. I went through that issue here.
These other Stack Overflow Questions that I've answered that show other parts (tangentially related):
Getting ListView Data Items from Objects
Working with ListViews
Concatenating Properties in a DropDownList

An option for getting non-object data to the UI is to create one or more lookup classes that are a bucket or "service" for getting odd bits of data for things like drop down lists etc...
Example:
myDDL.DataSource = Lookup.GetAllCountries(); // GetAllCountries is a static method
// set name/value fields etc...
myDDL.DataBind();
Using this methodology, you can still support tier separation. It's not object oriented or elegant, but it is very practical.

I don't know what's best practice, but what I do is I have a utility class that has a method that takes as arguments a DropDownList object and an enum, so I do
FillDropDown( ddlistPhoneType, DropDownTypes.PhoneTypes );
The utility class fills the dropdowns sometimes from the database, other times from XML, and occasionally some hardcoded values. But at least the GUI doesn't have to worry about that.