What is the difference between MVC and MVVM

Question

Is there a difference between the standard  Model View Controller  pattern and Microsoft s Model View ViewModel pattern

User · Answer

MVVM adds the view model into the mix  This is important  as it allows you to use a lot of the binding approach of WPF  without putting all that UI specific pieces in your regular model   I may be wrong  but I am not sure MVVM really forces the controller into the mix  I find the concept to be more in line with  http   martinfowler com eaaDev PresentationModel html  I think that people choose to combine it with MVC  not that it is built in into the pattern

User · Answer

It surprises me that this is a highly voted answers without mentioning the origin of MVVM  MVVM is a popular term used in Microsoft community and it is originated from Martin Fowler s Presentation Model  So to understand the motive of the pattern and the differences with others  the original article about the pattern is the first thing to read

User · Answer

The Controller is not replaced by a ViewModel in MVVM  because the ViewModel has a totally different functionality then a Controller  You still need a Controller  because without a Controller your Model  ViewModel and View will not do much    In MVVM you have a Controller too  the name MVVM is just missleading   MVVMC is the correct name in my humble opinion    As you can see the ViewModel is just an addition to the MVC pattern  It moves conversion-logic  for example convert object to a string  from the Controller to the ViewModel

User · Answer

From a practical point of view  MVC  Model-View-Controller  is a pattern   However  MVC when used as ASP net MVC  when combined with Entity Framework  EF  and the  power tools  is a very powerful  partially automated approach for bringing databases  tables  and columns to a web-page  for either full CRUD operations or R  Retrieve or Read  operations only   At least as I used MVVM  the View Models interacted with models that depended upon business objects  which were in turn  hand-made  and after a lot of effort  one was lucky to get models as good as what EF gives one  out-of-the-box    From a practical programming point of view  MVC seems a good choice because it gives one lots of utility out-of-box  but there is still a potential for bells-and-whistles to be added

User · Answer

The other answers might not be easy to understand for one who is not much familiar with the subject of architectural patterns  Someone who is new to app architecture might want to know how its choice can affect her app in practice and what all the fuss is about in communities   Trying to shed some light on the above  I made up this screenplay involving MVVM  MVP and MVC  The story begins by a user clicking on the    FIND    button in a movie search app       User  Click      View  Who   s that   MVVM MVP MVC   User  I just clicked on the search button      View  Ok  hold on a sec        MVVM MVP MVC     View calling the ViewModel Presenter Controller        MVVM MVP MVC   View  Hey ViewModel Presenter Controller  a User has just clicked on the search button  what shall I do   MVVM MVP MVC   ViewModel Presenter Controller  Hey View  is there any search term on that page   MVVM MVP MVC   View  Yes     here it is        piano     MVVM MVP MVC          This is the most important difference between MVVM AND MVP MVC            Presenter  Thanks View     meanwhile I   m looking up the search term on the Model  please show him her a progress bar  MVP MVC     Presenter Controller is calling the Model        MVP MVC   ViewController  Thanks  I   ll be looking up the search term on the Model but will not update you directly  Instead  I will trigger events to searchResultsListObservable if there is any result  So you had better observe on that   MVVM    While observing on any trigger in searchResultsListObservable  the View thinks it should show some progress bar to the user  since ViewModel would not talk to it on that                                                                                               ViewModel Presenter Controller  Hey Model  Do you have any match for this search term      piano     MVVM MVP MVC   Model  Hey ViewModel Presenter Controller  let me check      MVVM MVP MVC     Model is making a query to the movie database        MVVM MVP MVC     After a while                     This is the diverging point between MVVM  MVP and MVC                   Model  I found a list for you  ViewModel Presenter  here it is in JSON         name       Piano Teacher       year    2001      name       Piano       year    1993       MVVM MVP   Model  There is some result available  Controller  I have created a field variable in my instance and filled it with the result  It   s name is    searchResultsList     MVC    Presenter Controller thanks Model and gets back to the View   MVP MVC   Presenter  Thanks for waiting View  I found a list of matching results for you and arranged them in a presentable format      Piano Teacher 2001     Piano 1993      Also please hide the progress bar now  MVP   Controller  Thanks for waiting View  I have asked Model about your search query  It says it has found a list of matching results and stored them in a variable named    searchResultsList    inside its instance  You can get it from there  Also please hide the progress bar now  MVC   ViewModel  Any observer on searchResultsListObservable be notified that there is this new list in presentable format      Piano Teacher 2001     Piano 1993      MVVM   View  Thank you very much Presenter  MVP   View  Thank you    Controller     MVC   Now the View is questioning itself  How should I present the results I get from the Model to the user  Should the production year of the movie come first or last       View  Oh  there is a new trigger in searchResultsListObservable       good  there is a presentable list  now I only have to show it in a list  I should also hide the progress bar now that I have the result   MVVM   In case you are interested  I have written a series of articles here  comparing MVVM  MVP and MVC by implementing a movie search android app

User · Answer

Model   View   Controller  usually known as MVC  is a software design pattern commonly used for developing user interfaces that divide the related program logic into three interconnected elements  This is done to separate internal representations of information from the ways information is presented to and accepted by the user  Following the MVC architectural pattern decouples these major components allowing for code reuse and parallel development   Traditionally used for desktop graphical user interfaces  GUIs   this pattern has become popular for designing web applications  Popular programming languages like JavaScript  Python  Ruby  PHP  Java  and C  have MVC frameworks that are used in web application development straight out of the box   Model  The central component of the pattern  It is the application s dynamic data structure  independent of the user interface  It directly manages the data  logic  and rules of the application   View  Any representation of information such as a chart  diagram or table  Multiple views of the same information are possible  such as a bar chart for management and a tabular view for accountants   Controller  Accepts input and converts it to commands for the model or view   In addition to dividing the application into these components  the model   view   controller design defines the interactions between them   The model is responsible for managing the data of the application  It receives user input from the controller   The view means a presentation of the model in a particular format   The controller responds to the user input and performs interactions on the data model objects  The controller receives the input  optionally validates it and then passes the input to the model    Model   View   ViewModel  MVVM  is a software architectural pattern   MVVM facilitates a separation of development of the graphical user interface     be it via a markup language or GUI code     from the development of the business logic or back-end logic  the data model   The view model of MVVM is a value converter  meaning the view model is responsible for exposing  converting  the data objects from the model in such a way that objects are easily managed and presented  In this respect  the view model is more model than a view and handles most if not all of the view s display logic  The view model may implement a mediator pattern  organizing access to the back-end logic around the set of use cases supported by the view   MVVM is a variation of Martin Fowler s Presentation Model design pattern  MVVM abstracts a view s state and behavior in the same way  but a Presentation Model abstracts a view  creates a view model  in a manner not dependent on a specific user-interface platform   MVVM was invented by Microsoft architects Ken Cooper and Ted Peters specifically to simplify event-driven programming of user interfaces  The pattern was incorporated into Windows Presentation Foundation  WPF   Microsoft s  NET graphics system  and Silverlight  WPF s Internet application derivative   John Gossman  one of Microsoft s WPF and Silverlight architects  announced MVVM on his blog in 2005   Model   View   ViewModel is also referred to as model   view   binder  especially in implementations not involving the  NET platform  ZK  a web application framework written in Java  and KnockoutJS  a JavaScript library  use model   view   binder

User · Answer

MVC MVVM is not an either or choice  The two patterns crop up  in different ways  in both ASP Net and Silverlight WPF development  For ASP Net  MVVM is used to two-way bind data within views  This is usually a client-side implementation  e g  using Knockout js   MVC on the other hand is a way of separating concerns on the server-side  For Silverlight and WPF  the MVVM pattern is more encompassing and can appear to act as a replacement for MVC  or other patterns of organising software into separate responsibilities   One assumption  that frequently came out of this pattern  was that the ViewModel simply replaced the controller in MVC  as if you could just substitute VM for C in the acronym and all would be forgiven     The ViewModel does not necessarily replace the need for separate Controllers  The problem is  that to be independently testable   and especially reusable when needed  a view-model has no idea what view is displaying it  but more importantly no idea where its data is coming from   Note  in practice Controllers remove most of the logic  from the ViewModel  that requires unit testing  The VM then becomes a dumb container that requires little  if any  testing  This is a good thing as the VM is just a bridge  between the designer and the coder  so should be kept simple  Even in MVVM  controllers will typically contain all processing logic and decide what data to display in which views using which view models  From what we have seen so far the main benefit of the ViewModel pattern to remove code from XAML code-behind to make XAML editing a more independent task  We still create controllers  as and when needed  to control  no pun intended  the overall logic of our applications  The basic MVCVM guidelines we follow are   Views display a certain shape of data  They have no idea where the data comes from  ViewModels hold a certain shape of data and commands  they do not know where the data  or code  comes from or how it is displayed  Models hold the actual data  various context  store or other methods  Controllers listen for  and publish  events  Controllers provide the logic that controls what data is seen and where  Controllers provide the command code to the ViewModel so that the ViewModel is actually reusable   We also noted that the Sculpture code-gen framework implements MVVM and a pattern similar to Prism AND it also makes extensive use of controllers to separate all use-case logic  Don t assume controllers are made obsolete by View-models  I have started a blog on this topic which I will add to as and when I can  archive only as hosting was lost   There are issues with combining MVCVM with the common navigation systems  as most navigation systems just use Views and VMs  but I will go into that in later articles  An additional benefit of using an MVCVM model is that only the controller objects need to exist in memory for the life of the application and the controllers contain mainly code and little state data  i e  tiny memory overhead   This makes for much less memory-intensive apps than solutions where view-models have to be retained and it is ideal for certain types of mobile development  e g  Windows Mobile using Silverlight Prism MEF   This does of course depend on the type of application as you may still need to retain the occasional cached VMs for responsiveness  Note  This post has been edited numerous times  and did not specifically target the narrow question asked  so I have updated the first part to now cover that too  Much of the discussion  in comments below  relates only to ASP Net and not the broader picture  This post was intended to cover the broader use of MVVM in Silverlight  WPF and ASP Net and try to discourage people from replacing controllers with ViewModels

User · Answer

In very short - in MVC Controler is aware of  controls  view  while in MVVM  ViewModel is unaware of who consumes it  ViewModel exposes its observable properties and actions to whoever might be interested in using it  That fact makes testing easier since there is no reference to UI within ViewModel

User · Answer

I made a Medium article for this   MVVM   View   ViewModel   Model   The view has a reference to the ViewModel but not vice versa  The ViewModel has a reference to the Model but not vice versa  The View has no reference to the Model and vice versa    If you are using a controller  it can have a reference to Views and ViewModels  though a Controller is not always necessary as demonstrated in SwiftUI   Data Binding  we create listeners for ViewModel Properties      class CustomView  UIView     var viewModel   MyViewModel       didSet         self color   viewModel color              convenience init viewModel  MyViewModel        self viewModel   viewModel         struct MyViewModel      var viewColor  UIColor         didSet            colorChanged       This is where the binding magic happens                   var colorChanged    UIColor  - gt  Void       class MyViewController  UIViewController       let myViewModel   MyViewModel viewColor   green     let customView  CustomView      override func viewDidLoad           super viewDidLoad             This is where the binder is assigned        myViewModel colorChanged      weak self  color in          print  wow the color changed                 customView   CustomView viewModel  myViewModel        self view   customView          differences in setup   Business logic is held in the controller for MVC and the ViewModels for MVVM    Events are passed directly from the View to the controller in MVC while events are passed from the View to the ViewModel to the Controller  if there is one  for MVVM      Common features   Both MVVM and MVC do not allow the View to send messages directly to the Model s   Both have models    Both have views    Advantages of MVVM   Because the ViewModels hold business logic  they are smaller concrete objects making them easy to unit tests   On the other hand  in MVC  the business logic is in the ViewController   How can you trust that a unit test of a view controller is comprehensively safe without testing all the methods and listeners simultaneously  You can t wholly trust the unit test results      In MVVM  because business logic is siphoned out of the Controller into atomic ViewModel units  the size of the ViewController shrinks and this makes the ViewController code more legible      Advantages of MVC   Providing business logic within the controller reduces the need for branching and therefore statements are more likely to run on the cache which is more performant over encapsulating business logic into ViewModels   Providing business logic in one place can accelerate the development process for simple applications  where tests are not required   I don t know when tests are not required   Providing business logic in the ViewController is easier to think about for new developers

User · Answer

Simple Difference   Inspired by Yaakov s Coursera AngularJS course     MVC  Model View Controller    Models  Models contain data information  Does not call or use Controller and View  Contains the business logic and ways to represent data  Some of this data  in some form  may be displayed in the view  It can also contain logic to retrieve the data from some source  Controller  Acts as the connection between view and model  View calls Controller and Controller calls the model  It basically informs the model and or the view to change as appropriate  View  Deals with UI part  Interacts with the user      MVVM  Model View View Model   ViewModel    It is the representation of the state of the view    It holds the data that   s displayed in the view  Responds to view events  aka presentation logic  Calls other functionalities for business logic processing  Never directly asks the view to display anything

User · Answer

Microsoft provided an explanation of the MVVM Pattern in the Windows environment here    Here s a crucial section      In the Model-View-ViewModel design pattern  an app is composed of   three general components           Model  This represents the data model that your app consumes  For example  in a picture sharing app  this layer might represent the   set of pictures available on a device and the API used to read and   write to the picture library    View  An app typically is composed of multiple pages of UI  Each page shown to the user is a view in MVVM terminology  The view is   the XAML code used to define and style what the user sees  The data   from the model is displayed to the user  and it   s the job of the   ViewModel to feed the UI this data based on the current state of the   app  For example  in a picture sharing app  the views would be the UI   that show the user the list of albums on the device  the pictures in   an album  and perhaps another that shows the user a particular   picture    ViewModel  The ViewModel ties the data model  or simply the model  to the UI  or views  of the app  It contains the logic with   which to manage the data from the model and exposes the data as a set   of properties to which the XAML UI  or views  can bind  For example    in a picture sharing app  the ViewModel would expose a list of albums    and for each album expose a list of pictures  The UI is agnostic of   where the pictures come from and how they are retrieved  It simply   knows of a set of pictures as exposed by the ViewModel and shows them   to the user

User · Answer

MVVMC  or perhaps MVC   seems to be a viable approach for enterprise as well as rapid application development  While it is nice to separate the UI from business and interaction logic  the  pure  MVVM pattern and most available examples work best on singular views    Not sure about your designs  but most of my applications  however  contain pages and several  reusable  views and thus the ViewModels do need to interact to some degree  Using the page as controller would defeat the purpose of the MVVM altogether  so not using a  VM-C  approach for the underlying logic might result in    well    challenging constructs as the application matures  Even in VB-6 most of us probably stopped coding business logic into the Button event and started  relaying  commands to a controller  right    I recently looked at many emerging framworks on that topic  my favorite clearly is the Magellan  at codeplex  approach  Happy coding    http   en wikipedia org wiki Model View ViewModel References

User · Answer

Injecting Strongly Typed ViewModels into the View using MVC  The controller is responsible for newing up the ViewModel and injecting it into the View   for get requests  The ViewModel is the container for DataContext and view state such as the last selected item etc  The Model contains DB entities and is very close to the DB Schema it does the queries and filtering   I like EF and LINQ for this  The Model should also consider repositories and or projection of results into strong types  EF has a great method     EF Database Select querystring  parms  for direct ADO access to inject queries and get back strong types   This addresses the EF is slow argument  EF is NOT SLOW  The ViewModel gets the data and does the business rules and validation The controller on post back will cal the ViewModel Post method and wait for results  The controller will inject the newly updated Viewmodel to the View  The View uses only strong type binding  The view merely renders the data  and posts events back to the controller   see examples below  MVC intercepts the inbound request and routes it to proper controller with strong data type  In this model there is no more HTTP level contact with the request or response objects as MSFT s MVC machine hides it from us  In clarification of item 6 above  by request     Assume a ViewModel like this  public class myViewModel       public string SelectedValue  get set   public void Post          due to MVC model binding the SelectedValue string above will be set by MVC model binding on post back        this allows you to do something with it      DoSomeThingWith SelectedValue       SelectedValue    quot Thanks for update  quot         The controller method of the post will look like this  See below   note that the instance of mvm is automatically instanciated by the MVC binding mechanisms   You never have to drop down to the query string layer as a result  This is MVC instantiating the ViewModel for you based on the query strings   HTTPPOST     public ActionResult MyPostBackMethod  myViewModel mvm            if  ModelState IsValid                              Immediately call the only method needed in VM                   mvm Post                   return View mvm      Note that in order for this actionmethod above to work as you intend  you must have a null CTOR defined that intializes things not returned in the post   The post back must also post back name value pairs for those things which changed   If there are missing name value pairs the MVC binding engine does the proper thing which is simply nothing   If this happens you might find yourself saying  quot I m losing data on post backs quot     The advantage of this pattern is the ViewModel does all the  quot clutter quot  work interfacing to the Model Buisness logic  the controller is merely a router of sorts   It is SOC in action

User · Answer

Complementary to many of the responses given  I wanted to add some additional perspective from the Modern client-side web - or Rich Web Application point of view   Indeed these days simple web sites and larger web applications are commonly built with many popular libraries such as Bootstrap  Built by Steve Sanderson  Knockout provides support for the MVVM pattern which mimics one of the most important behaviors in the pattern  data-binding through the View Model  With a little JavaScript  data and logic can be implemented that can then be added to page elements with simple data-bind HTML attributes  similar to using many of the features of Bootstrap  Together  these two libraries alone offer interactive content  and when combined with routing this approach can result in a simple-yet-powerful approach to building the Single Page Application   Similarly  a Modern client-side framework such as Angular follows the MVC pattern by convention  but also adds a Service  Interestingly  it is touted as Model-View-Whatever  MVW    See this post on Stack Overflow    Additionally  with the rise of Progressive web frameworks such as Angular 2  we re seeing a change in terminology and perhaps a new architectural pattern where Components comprise of a View or Template and interact with a Service - all of which can be contained in a Module  and a series of Modules makes up the application

User · Answer

From what I can tell  the MVVM maps to the MV of MVC - meaning that in a traditional MVC pattern the V does not communicate directly with the M  In the second version of MVC  there is a direct link between M and V  MVVM appears to take all tasks related to M and V communication  and couple it to decouple it from the C  In effect  there s still the larger scope application workflow  or implementation of the use scenarios  that are not fully accounted for in MVVM  This is the role of the controller  By removing these lower level aspects from the controllers  they are cleaner and makes it easier to modify the application s use scenario and business logic  also making controllers more reusable

User · Answer

I thought one of the main differences was that in MVC  your V reads your M directly  and goes via the C to manipulate the data  whereas in MVVM  your VM acts as an M proxy  as well as providing the available functionality to you V   If I m not full of junk  I m surprised no one has created a hybrid  where your VM is merely a M proxy  and C provides all functionality

User · Answer

I think the easiest way to understand what these acronyms are supposed to mean is to forget about them for a moment  Instead  think about the software they originated with  each one of them  It really boils down to just the difference between the early web and the desktop   As they grew in complexity in the mid-2000s  the MVC software design pattern - which was first described in the 1970s - began to be applied to web applications  Think database  HTML pages  and code inbetween  Let s refine this just a little bit to arrive at MVC  For   database    let s assume database plus interface code  For   HTML pages    let s assume HTML templates plus template processing code  For   code inbetween    let s assume code mapping user clicks to actions  possibly affecting the database  definitely causing another view to be displayed  That s it  at least for the purpose of this comparison   Let s retain one feature of this web stuff  not as it is today  but as it existed ten years ago  when JavaScript was a lowly  despicable annoyance  which real programmers did well to steer clear of  The HTML page is essentially dumb and passive  The browser is a thin client  or if you will  a poor client  There is no intelligence in the browser  Full page reloads rule  The   view   is generated anew each time around   Let s remember that this web way  despite being all the rage  was horribly backward compared to the desktop  Desktop apps are fat clients  or rich clients  if you will   Even a program like Microsoft Word can be thought of as some kind of client  a client for documents   They re clients full of intelligence  full of knowledge about their data  They re stateful  They cache data they re handling in memory  No such crap as a full page reload   And this rich desktop way is probably where the second acronym originated  MVVM  Don t be fooled by the letters  by the omission of the C  Controllers are still there  They need to be  Nothing gets removed  We just add one thing  statefulness  data cached on the client  and along with it intelligence to handle that data   That data  essentially a cache on the client  now gets called   ViewModel    It s what allows rich interactivity  And that s it    MVC   model  controller  view   essentially one-way communication   poor interactivity MVVM   model  controller  cache  view   two-way communication   rich interactivity   We can see that with Flash  Silverlight  and - most importantly - JavaScript  the web has embraced MVVM  Browsers can no longer be legitimately called thin clients  Look at their programmability  Look at their memory consumption  Look at all the Javascript interactivity on modern web pages   Personally  I find this theory and acronym business easier to understand by looking at what it s referring to in concrete reality  Abstract concepts are useful  especially when demonstrated on concrete matter  so understanding may come full circle    nbsp

User · Answer

The viewmodel is an  abstract  model for your user interface elements  It must allow you to execute the commands  and actions in your view in a non-visual way  for example to test it    If you have worked with MVC  you probably have sometime found useful to create model objects to reflect the state of your view  for example  to show and hide some edit dialog  etc  In that case you are using a viewmodel   The MVVM pattern is simply the generalization of that practice to all the UI elements    And it s not a Microsoft pattern  what appends is that WPF   Silverlight data-bindings are specially well-suited to work with this pattern  But nothing stops you to use it with java server faces  for example

User · Answer

MVVM Model-View ViewModel is similar to MVC  Model-View Controller  The controller is replaced with a ViewModel  The ViewModel sits below the UI layer  The ViewModel exposes the data and command objects that the view needs  You could think of this as a container object that view goes to get its data and actions from  The ViewModel pulls its data from the model   Russel East does a blog discussing more in detail  Why is MVVM is different from MVC

User · Answer

I used to think that MVC and MVVM are the same  Now because of the existence of Flux I can tell the difference   In MVC  for each view in your app  you have a model and a controller  so I would call it view  view model  view controller  The pattern does not tell you how one view can communicate with another  Therefore  in different frameworks there are different implementations for that  For example there are implementations where controllers talk to each other whereas in other implementations there s another component that mediates between them  There are even implementations in which the view models communicate with each other  which is a break of the MVC pattern because the view model should only be accessed by the view controller   In MVVM  you also have a view model for each component  The pattern does not specify how the heck the view should influence the view model  so usually most frameworks just include controller s functionality in the view model  However  MVVM does tell you that your view model s data should come from the model  which is the entire model that s not aware or custom to a specific view   To demonstrate the difference  let s take Flux pattern  Flux pattern tells how different views in the app should communicate  Each view listens to a store and fires actions using the dispatcher  The dispatcher in turn tells all the stores about the action that was just made  and the stores update themselves  A store in Flux corresponds to the  general  model in MVVM  it s not custom to any specific view  So usually when people use React and Flux  each React component actually implements the MVVM pattern  When an action occurs  the view model calls the dispatcher  and finally it s getting updated according to the changes in the store  which is the model  You can t say that each component implements MVC because in MVC only the controller can update the view model  So MVVM can work with Flux together  MVVM handles the communication between the view and the view model  and Flux handles the communication between different views   whereas MVC can t work with Flux without breaking a key principle

User · Answer

For one thing  MVVM is a progression of the MVC pattern which uses XAML to handle the display   This article outlines some of the facets of the two      The main thrust of the Model View ViewModel architecture seems to be that on top of the data     the Model      there   s another layer of non-visual components     the ViewModel     that map the concepts of the data more closely to the concepts of the view of the data     the View      It   s the ViewModel that the View binds to  not the Model directly

User · Answer

Well  generally MVC is used in Web development and MVVM is most popular in WPF Silverlight development  However  sometimes the web architecute might have a mix of MVC and MVVM   For example  you might use knockout js and in this case you will have MVVM on your client side  And your MVC s server side can also change  In the complex apps  nobody uses the pure Model  It might have a sense to use a ViewModel as a  Model  of MVC and your real Model basically will be a part of this VM  This gives you an extra abstraction layer

User · Answer

MVC is a controlled environment and MVVM is a reactive environment    In a controlled environment you should have less code and a common source of logic  which should always live within the controller   However  in the web world MVC easily gets divided into view creation logic and view dynamic logic   Creation lives on the server and dynamic lives on the client   You see this a lot with ASP NET MVC combined with AngularJS whereas the server will create a View and pass in a Model and send it to the client   The client will then interact with the View in which case AngularJS steps in to as a local controller   Once submitted the Model or a new Model is passed back to the server controller and handled   Thus the cycle continues and there are a lot of other translations of this handling when working with sockets or AJAX etc but over all the architecture is identical    MVVM is a reactive environment meaning you typically write code  such as triggers  that will activate based on some event   In XAML  where MVVM thrives  this is all easily done with the built in databinding framework BUT as mentioned this will work on any system in any View with any programming language   It is not MS specific   The ViewModel fires  usually a property changed event  and the View reacts to it based on whatever triggers you create   This can get technical but the bottom line is the View is stateless and without logic   It simply changes state based on values   Furthermore  ViewModels are stateless with very little logic  and Models are the State with essentially Zero logic as they should only maintain state   I describe this as application state  Model   state translator  ViewModel   and then the visual state   interaction  View    In an MVC desktop or client side application you should have a Model  and the Model should be used by the Controller   Based on the Model the controller will modify the View  Views are usually tied to Controllers with Interfaces so that the Controller can work with a variety of Views   In ASP NET the logic for MVC is slightly backwards on the server as the Controller manages the Models and passes the Models to a selected View  The View is then filled with data based on the model and has it s own logic  usually another MVC set such as done with AngularJS    People will argue and get this confused with application MVC and try to do both at which point maintaining the project will eventually become a disaster   ALWAYS put the logic and control in one location when using MVC   DO NOT write View logic in the code behind of the View  or in the View via JS for web  to accommodate Controller or Model data   Let the Controller change the View  The ONLY logic that should live in a View is whatever it takes to create and run via the Interface it s using   An example of this is submitting a username and password   Whether desktop or web page  on client  the Controller should handle the submit process whenever the View fires the Submit action   If done correctly you can always find your way around an MVC web or local app easily   MVVM is personally my favorite as it s completely reactive   If a Model changes state the ViewModel listens and translates that state and that s it     The View is then listening to the ViewModel for state change and it also updates based on the translation from the ViewModel   Some people call it pure MVVM but there s really only one and I don t care how you argue it and it s always Pure MVVM where the View contains absolutely no logic     Here s a slight example   Let s say the you want to have a menu slide in on a button press   In MVC you will have a MenuPressed action in your interface   The Controller will know when you click the Menu button and then tell the View to slide in the Menu based on another Interface method such as SlideMenuIn   A round trip for what reason   Incase the Controller decides you can t or wants to do something else instead that s why   The Controller should be in charge of the View with the View doing nothing unless the Controller says so   HOWEVER  in MVVM the slide menu in animation should be built in and generic and instead of being told to slide it in will do so based on some value   So it listens to the ViewModel and when the ViewModel says  IsMenuActive   true  or however  the animation for that takes place   Now  with that said I want to make another point REALLY CLEAR and PLEASE pay attention   IsMenuActive is probably BAD MVVM or ViewModel design   When designing a ViewModel you should never assume a View will have any features at all and just pass translated model state   That way if you decide to change your View to remove the Menu and just show the data   options another way  the ViewModel doesn t care   So how would you manage the Menu   When the data makes sense that s how   So  one way to do this is to give the Menu a list of options  probably an array of inner ViewModels    If that list has data  the Menu then knows to open via the trigger  if not then it knows to hide via the trigger   You simply have data for the menu or not in the ViewModel   DO NOT decide to show    hide that data in the ViewModel   simply translate the state of the Model   This way the View is completely reactive and generic and can be used in many different situations     All of this probably makes absolutely no sense if you re not already at least slightly familiar with the architecture of each and learning it can be very confusing as you ll find ALOT OF BAD information on the net    So    things to keep in mind to get this right   Decide up front how to design your application and STICK TO IT     If you do MVC  which is great  then make sure you Controller is manageable and in full control of your View  If you have a large View consider adding controls to the View that have different Controllers   JUST DON T cascade those controllers to different controllers   Very frustrating to maintain   Take a moment and design things separately in a way that will work as separate components    And always let the Controller tell the Model to commit or persist storage   The ideal dependency setup for MVC in is View   Controller   Model  or with ASP NET  don t get me started  Model   View   Controller   Model  where Model can be the same or a totally different Model from Controller to View     of course the only need to know of Controller in View at this point is mostly for endpoint reference to know where back to pass a Model   If you do MVVM  I bless your kind soul  but take the time to do it RIGHT   Do not use interfaces for one   Let your View decide how it s going to look based on values   Play with the View with Mock data   If you end up having a View that is showing you a Menu  as per the example  even though you didn t want it at the time then GOOD   You re view is working as it should and reacting based on the values as it should   Just add a few more requirements to your trigger to make sure this doesn t happen when the ViewModel is in a particular translated state or command the ViewModel to empty this state   In your ViewModel DO NOT remove this with internal logic either as if you re deciding from there whether or not the View should see it  Remember you can t assume there is a menu or not in the ViewModel   And finally  the Model should just allow you to change and most likely store state   This is where validation and all will occur  for example  if the Model can t modify the state then it will simply flag itself as dirty or something   When the ViewModel realizes this it will translate what s dirty  and the View will then realize this and show some information via another trigger   All data in the View can be binded to the ViewModel so everything can be dynamic only the Model and ViewModel has absolutely no idea about how the View will react to the binding   As a matter of fact the Model has no idea of a ViewModel either   When setting up dependencies they should point like so and only like so View   ViewModel   Model   and a side note here    and this will probably get argued as well but I don t care    DO NOT PASS THE MODEL to the VIEW unless that MODEL is immutable  otherwise wrap it with a proper ViewModel   The View should not see a model period   I give a rats crack what demo you ve seen or how you ve done it  that s wrong    Here s my final tip    Look at a well designed  yet very simple  MVC application and do the same for an MVVM application   One will have more control with limited to zero flexibility while the other will have no control and unlimited flexibility   A controlled environment is good for managing the entire application from a set of controllers or  a single source  while a reactive environment can be broken up into separate repositories with absolutely no idea of what the rest of the application is doing   Micro managing vs free management    If I haven t confused you enough try contacting me    I don t mind going over this in full detail with illustration and examples   At the end of the day we re all programmers and with that anarchy lives within us when coding    So rules will be broken  theories will change  and all of this will end up hog wash    But when working on large projects and on large teams  it really helps to agree on a design pattern and enforce it   One day it will make the small extra steps taken in the beginning become leaps and bounds of savings later

User · Answer

mvc is server-side and mvvm is client-side browser  in web development   most of the time javascript is used for mvvm in browser  there are many server side technologies for mvc

User · Answer

MVVM is a refinement  debatable  of the Presentation Model pattern   I say debatable  because the only difference is in how WPF provides the ability to do data binding and command handling

[model-view-controller] What is the difference between MVC and MVVM?

Examples related to model-view-controller

Examples related to mvvm

Examples related to design-patterns