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Questions tagged [mvvm]

The Model View ViewModel (MVVM) is an architectural pattern used in software engineering that originated from Microsoft as a specialization of the presentation model design pattern introduced by Martin Fowler.

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80 views

Where should objects be built from view-models in a layered architecture?

Having the following classes: Person.cs namespace Project.Domain { public class Person { public int Id { get; set; } public string Name { get; set; } public decimal ...
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1answer
70 views

Provide overall application status in global exception handler/crash report

In my UI application (WPF/C#, using MVVM design pattern), I have implemented a global exception handler which catches all unexpected (hence uncaught) exceptions and reports the application crash to ...
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1answer
49 views

Throttling notifications from child ViewModel to parent ViewModel

I have a child view-model which notifies on a property change: public class ChildViewModel : INotifyPropertyChanged { private bool isSelected; public bool IsSelected { get => ...
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1answer
137 views

What is the correct architecture for 4 MVVM synchronized collections related to groups and filters inside a WPF application?

I have a small architectural problem with MVVM. In this question I will note Model through M and ViewModel through VM. I have 4 collections that must be synchronized, and the items in them must have ...
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31 views

How to implment MVVM patern for editing a shared class instance?

I'm struggling with architecture for a few related programs and libraries. Primarily with how to handle editing properties of a model class instance across multiple views and where to implement ...
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1answer
131 views

Do shared ViewModels contradict MVVM?

I want to follow the MVVM app architecture. I also need to have some communication between some fragments. But the official approach is pretty confusing. Taken from the docs (https://developer....
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1answer
97 views

IoC/DI + “normal” constructor arguments mvvm

I am using unity in C# to achieve dependency injection and inversion of control. What if i have a class, lets say a viewmodel, that depends on several services like a repository, a validator and a ...
0
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1answer
58 views

When to fetch/send data in an Android application

I am currently creating an Android application and I have the following questions: We have a server which provides data for the app in form of a REST-JSON-API. The App is following the MVVM ...
0
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1answer
340 views

Check location permissions with MVVM in Android?

I need to request runtime location permissions for the FusedLocationProviderClient api and, once I have them, obtain Location objects and feed them to an algorithm that will make a query to an ...
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0answers
58 views

How to avoid circular dependency from abstracting navigation in desktop application?

I am trying to abstract some functionality from my desktop application (JavaFX) for changing views. So, what I am thinking is: Navigator interface with methods like goToAccountsOverview(), ...
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2answers
189 views

Is it okay to pass my model into my view model via its constructor through MVVM practices?

public class LDLTrackViewModel : RailwayViewModel { private LDLTrack _ldlTrack; public LDLTrack LDLTrack { get => _ldlTrack; set { _ldlTrack = value; ...
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1answer
94 views

How to populate view models

So let's say I have a view model, representing a student. The view model is corresponding to a student model, from which the data comes. What I am struggling with, is how to populate the fields in the ...
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1answer
111 views

Where to store calculated values of an entity

Trying to figure out the best place to store calculated properties related to a base entity class for use through out the application, namely in view models and DTOs. For example, a base entity class ...
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1answer
148 views

Setters in ViewModels

So I have started reading some books and articles on architecture. They all state (put a little simply) that you should never let your view access the model directly, when using a Model-View-ViewModel ...
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1answer
69 views

Where do I save a Canvas “center position” coordinate in an MVVM architecture?

Assume I have a canvas that has rendered shapes. I can drag-move around that canvas as if I was in a zoomed in image to move all shapes around. Between the Model and ViewModel I have a ServiceLayer (...
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3answers
259 views

How to avoid duplication of types in MVVM

I'm learning the MVVM pattern and something that comes up often is a duplication of data-types. Say I have a Person datatype. Intuitively I want it to look like this: public class Person { ...
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1answer
114 views

Designing a WPF / MVVM architecture where view behavior changes in different states

As part of my bachelors thesis, I'm trying to develop something akin to a painting program. That means, I have a toolset, be it selection, drawing, highlighting, etc. I'll have a canvas that displays ...
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1answer
233 views

What is the proper way to change the View from a ViewModel when using the MVVM pattern?

I'm trying to follow the Model–View–ViewModel pattern in a Xamarin application and am wondering how the View should be able to change when a given ViewModel is finished. Below I have listed the ideas ...
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0answers
70 views

Changing UserControl based on property in ViewModel

I want to change the view inside of a ContentControl based on an enum property in the ViewModel for the Window hosting these controls. Below are two sample UserControls: <UserControl x:Class="...
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0answers
159 views

Xamarin.Forms and Prism NavigationParameters implementation

I am developing a Xamarin Forms project and use Prism Library as tool to implement the MvvM pattern. I have two views: PersonViewModel: Summary and has Edit button PersonEditViewModel: Details, and ...
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3answers
161 views

How do I architect an iOS app when multiple view models must know when the model has changed?

I'm using MVVM and I have an app with a UITabBarController, the Main tab of which is a list of publications and the other is a Search screen where they can search for publications. Searching returns a ...
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0answers
75 views

When not to use View Services in MVVM design pattern?

I'm using the MVVM design pattern in my application which is comprised of, A Xamarin.IOs project (View Layer) A Net Standard project (Common Layer) A Xamarin.Android project (in the future) (View ...
2
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1answer
1k views

Why can’t ViewModels communicate with each other?

Can someone explain concretely why it is not desirable for ViewModels to communicate directly with other view models? It seems to me that for virtually any UX application there will be a “root” view (...
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2answers
152 views

What is better approach to implement dependency injection using MVVM Architecture?

I need to use DispatchQueue within controller and pass it as dependency. This is what I have tried so far and worked out two solutions. Need to ask what is better and in common use by other developers:...
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1answer
85 views

MVVM/WPF/Appropriate place for code

I have a question about MVVM design, and where I should put some code that I would like to add. My application queries active directory for computers and displays the list to the user. Selecting a ...
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1answer
975 views

When to use The Messenger (Mediator) Pattern in MVVM design

I got confused with the role of the Messenger in MVVM. I see contradictory articles about it. This Article by MSDN by: Communicating from the View-Model to the View Observant readers will ...
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2answers
359 views

Propagating Data to multiple ViewModels - C#

I'm a bit new to MVVM, but here's my dilemma: I have a model (or models, but let's keep it simple) I want to show that model data on multiple different views. Ok, so ViewModel for each view gets ...
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2answers
3k views

Clean Architecture: What is the View Model?

In his book 'Clean Architecture', Uncle Bob says that the Presenter should put the data that it receives into something he calls the 'View Model'. Is this the same thing as the 'ViewModel' from the ...
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2answers
273 views

How should I Implement a general method that could be used across several view models?

Currently I have implemented a method in to a model to take a screen shot like so E.G. Interface public interface ICapture { void CaptureMethod(); } This is the model that implements that ...
5
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1answer
400 views

Where is it better to implement Copy/Cut/Paste in MVVM?

I am working on a project using C#/WPF and following MVVM pattern. This project is designed for touch screens. The major objects of the program are the following: We have Programs which contain ...
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1answer
421 views

Giving Viewmodels access to application wide Model in MVVM

I am practicing building applications using MVVM and WPF+C# by making a "finance application". The application contains several views with their own ViewModels. The views are in a hierarchy and are ...
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1answer
151 views

MVC / MVVM principles

I'm currently working on updating some old projects (inherited stuff) and I keep running into various small issues with the architecture. Namely monolithic classes too tightly coupled. One example ...
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3answers
368 views

When to use Parameters and When Not to C#

I am have an application using MVVM pattern. It takes a user ID and returns a table with the user's bookmarks. I am trying to decided if it is better practice to include parameters in my model's ...
5
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1answer
433 views

Approach for Constructing View Models in Complex MVVM Application

I'm struggling with the design in a WPF MVVM application. In a few courses I've taken, they say that having a lot of parameters in a constructor is a code smell, but they never address how to deal ...
3
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1answer
105 views

View-model architecture

I have two screens: A screen with a list of items, where every item in the list has "Show Details" and "Update buttons" An item details screen. The "Show Details" button navigates to item details ...
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3answers
1k views

State of selected items in view or viewmodel?

Myself and my colleague were having a discussion about MVVM and how lists and selected items should be stored in view / viewmodel. I think the viewmodel should only offer up the data and allow the ...
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1answer
177 views

MVC: How to use data model list in recursive views

I am trying to learn web app MVC in PHP.Most of the articles discussed about 1-to-1 MVC pattern given bellow Controller: gets user request & update model, Model: receives orders form Controller &...
3
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0answers
62 views

How does “redux” decouple the different components so they can be tested separately in unit tests?

In the past we saw a big move from traditional MVC to MVVM for user interfaces: One of the primary motivations for MVVM is that the view and viemmodel are competely indepedently of each other and ...
1
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1answer
118 views

MVVM distinguish between Model and View-Model and Models relashionships on reactive architecture

This should be a simple MVVM - reactive architecture question, something that I miss probably. I'll start with a context example: I have a Music Tracks Player application with 2 models Player and ...
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0answers
2k views

Proper implementation of Repository Pattern with MVVM in WPF

I am currently refactoring a WPF application that is built on the principles of the Repository Pattern. It uses Entity Framework as its ORM, and is Database First. Each of those entities is wrapped by ...
0
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1answer
137 views

Adding an additional layer between domain model and view model necessary?

I am working on a Xamarin application (Mvvm using Prism), I am also leveraging OData for communication between my backend and the mobile application. The structure of my Mobile app is as follows: ...
0
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1answer
82 views

Ext JS: Designing a base class and override it

I'm trying to define a base class and override it's items on different inherited sub-classes. I'm following MVVM pattern to fetch records from backend. Created several stores and formulas within ...
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0answers
244 views

Should I populate view model inside or before creating it

I'm not sure if softwareengineering exchange is right for the question. I need to populate view model with some values I query from the database. I do it like: var db = new NPoco.Database(...
2
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1answer
288 views

ASP.Net MVC When ViewModel properties vs Ajax calls in view

When is it more appropriate to use asynchronous calls from the view to get data vs prepopulating it server-side when creating the instance of the viewmodel? For instance, if my view has some dropdown ...
0
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4answers
632 views

Avoid type checking but preserve separation of concerns

I'm working on an MVVM project and trying to preserve separation of concerns. Our current architecture has an entity framework model and MVVM light view and viewmodel projects. I'm working ViewModel ...
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2answers
654 views

MVVM. Is it a code smell when view model has properties with names show/hide/display that semantically belong to view?

I've lately been involved with WPF and looked into MVVM. I understand that view model shouldn't be aware of view. However, sometimes I come across situation where my initial instinct is to write ...
3
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2answers
2k views

Adding model into another view model's collection

The Setup So I'm working on a project in which there exists a MainViewModel class. This MainViewModel contains a list of Soldiers through an observable collection. I have a button in the MainView ...
2
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1answer
102 views

Thick viewmodel results in thin model

How thick should a viewmodel be? For example, should my viewmodel or model handle the actual filtering? For example, let's say I have a Roster object holding a collection of Users which are ...
2
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1answer
288 views

What's the M in MVVM?

Is the M (model) in MVVM equal to business logic + data? Or is it just supposed to be data/state for the view? Background: In a project we use "model" as a name for an object that holds presentation ...
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2answers
3k views

Overall view validation with a datagrid and keeping to MVVM

I am struggling to find a good architecture for what must be a common problem Enable/Disable a button in a View that contains a datagrid, and has validation requirements on the cell, row and ...