How do multiple layers work in the MVVM pattern? - c#

I am trying to get my head around MVVM. For a simple list->data view it's no problem. But I am struggling to understand how multiple layers work. I sort of have something working but it's very hit and miss as to which bits work and which bits don't. For example, some data updates, some doesn't. Anything in a deeper level which should affect a list at an upper level sometimes updates the list, sometimes doesn't. There must be a pattern but I have yet to spot it. Does anybody know of any tutorials with more than just a list->data type of view?
Example:
List of widgets
+- Widget name
+- Widget description
+- List of Widget parts
+- Part ID
+- Colour
In that example I could have a three-column approach - list of widgets in the left, widget information in the middle including the parts list, and then the part detail on the right.

You should have multiple ViewModels, one for each level.
Then you can provide events to let the upper levels update on change.
For example you can have a
public class WidgetListViewModel
{
public ObservableCollection<WidgetViewModel> Widgets {get; set; }
}
public class WidgetViewModel
{
public string WidgetName { get; set; }
public string WidgetDescription { get; set; }
public ObservableCollection<WidgetPartViewModel> Parts { get; set; }
}
public class WidgetPartViewModel
{
public int PartId { get; set; }
public System.Windows.Media.Color Color { get; set; }
}
Having events (including a simple pattern) is described here Events in .Net
Furthermore, I recommend watching this excellent video tutorial on MVVM:
Jason Dollinger on MVVM
The video covers some issues of Unity also! (which could be very valuable for you)
The sourcecode he developes is also available:
Lab49 Sourcecode by Jason Dollinger

Related

Understanding Model & ViewModel in WebView/WinForm in MVP/MVC

I am trying to understand and implement different UI patterns in .NET to see the pros and cons and where they suite best.
I understand the main concept but I was creating an app and a question appeared.
Say we have a class Customer, which represents the core Information of a customer.
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string Country { get; set; }
public string PostalCode { get; set; }
public string PhoneNumber { get; set; }
}
Now, if I create a WebView or WebForm to show all customers I can use this class to set as source f.e. to a DGV, being able to show all properties above.
But then I want to show for example a View/Form with the Revenue history of each customer.
So there is a class CustomerRevenue like
public class CustomerRevenue
{
public Revenue ActualYearExpectedRevenue { get; set; }
public IList<Revenue> RevenuePerYearList { get; set; }
public decimal ActualYearProjectedRevenue => CalculateYearProyection();
public decimal CalculateYearProyection(int year)
{
var daysInYear = DateTime.IsLeapYear(year) ? 365 : 366;
var actualYearRevenue = RevenuePerYearList.SingleOrDefault(x => x.Year == year);
var dayNumber = DateTime.Now.DayOfYear;
var projection = ((actualYearRevenue.Amount * daysInYear) / dayNumber);
return projection;
}
}
Here, to set RevenuePerYearList we need some time, since let's say we sell a lot and have a huge list of sells with huge lists of articles, so the calculation needs some time.
So now my question:
Should I then have "concrete" classes for each view/model with the data I want to show, i.e. here I would have apart of Customer class, say a CustomerRevenueModel
public class CustomerRevenueModel
{
private readonly CustomerRevenue _customerRevenue = new CustomerRevenue();
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string Country { get; set; }
public string PostalCode { get; set; }
public CustomerRevenue CustomerRevenue
{
get { return _customerRevenue; }
}
}
}
which has (maybe) different properties, so I need to load this "heavy" properties when needed
or
should I stay with only one class (I mean, a customer always has a revenue) and leave the properties "empty"?
The first option makes me have a lot of classes, one for each view/form I want to show data for (maybe being able to reuse some models in various views/forms) but keeps all clean and in a valid state. And also each class can have it's own logic (domain logic - DDD)
The second option is less classes, less code, but some way I end having a huge (God) class, with all the properties a Customer has and all it's logic (methods). I load only the ones I need, but this appears really bad to me.
The third option is to have the big class with all properties and methods as my (domain)model, and create a "ViewModel" (which contains no methods, only props) each time I need to show sth. like above , using it as source for my GridView. This is the solution with more classes and code (big class + ViewModels + (maybe) DTOs), but also the more organized and SOLID design to my eyes... Here the use of a Mapper like AutoMapper would really help, mapping between objects
But this is the part I'm confused about...
Are these "ViewModels" a bad pattern using MVC or MVP?
Are this the same as the VM in MVVM? Which I Think not, since I've understood VM in MVVM like a "template", but what I talk about appears to me more like DAOs??
Or they don't have nothing to do, are just DAOs
I think I am a bit confused about all the different meanings of Model, ViewModel etc, in the different design patterns.
I am hardly trying to understand right MVC,MVP,MVVM and DDD and I think sometimes I am mixing terms...?
First, try to not "mix" things from different patterns, ViewModels are for MVVM, and you NEED ViewModels if you want to implement MVVM (ASP.Net MVC uses something called ViewModels, but it is not the same than the ViewModels in MVVM design pattern)
The ViewModel is like a model for the View. The ViewModel work is to "convert" the Model(s) to something the View can understand.
You can have one o more models (or none) and use it in the ViewModel, you have a ViewModel for each View.
In your example (a datagridview) you can have a model that will represent the data in a datagridview, a DTO if you want, and you can have a property in the ViewModel, a List and you will fill with data loaded from the database. In the View, you will bind that property (the list) to the dgv datasource.
Think that the ViewModel is something like the code behind of the view, but you are working with properties and commands that will be binded to controla in the view.

Create code from Pattern Graph

I got a graph from which I need to set some propery in objects. Im adding an example on which I will explain it better:
Assuming I have the following class:
public class Person
{
public int Account { get; set; }
public string BirthCity { get; set; }
public string Name { get; set; }
public Family Family { get; set; }
}
Each Person that gets to the DAL will automatically be assigned with Status according to that algorythm. My real problem is much more complex, but this example does explain it well I think.
The graph describes scenarios and I need to translate it to code. I want my solution to be as flexible to changes as possible. Ofcourse writing ifs and switch case is the easiest yet its not a good solution.
One idea I had was creating an Xml file suting the scenarios, but I think that it might not be that good.
Does anyone have any Ideas about this issue?

RPG Doors / Events

Heeeey, on my RPG i'm working on i have a working tile engine which you can add layers, i have three layers:
Bottom Layer
Top Layer
Solid Layer
I have collision working and also the character animation working.
But how would i go making doors, that when you walk into them and have a key, it switches to another map?
I tried to add another layer called "EventLayer" but i don't know how to format it properly to work.. And things like Events - For example a falling book, sound effect...
Could someone please help me with this?
Thanks in advance! :)
Events like this will be a lot different based on what exactly you need in your game.
If you want events to only be doors and similar interactable objects, and have NPCs and monsters etc. in their own type, then events are not that tough to make.
You need to include every property you need to have for all your events, such as the position, graphic and trigger type. In your case, you want certain events only to function when certain items are in possession. Add a requirement list, and make sure everything in that list is met before executing the corresponding event.
When programming your event objects, you might want to make them universal, so you can create most (if not all) of your events from this instances of this class. Example of a quick event class mockup:
class Event {
public Texture2D Graphic { get; set; }
public Vector2 TileLocation { get; set; }
public List<Condition> Conditions { get; set; }
public TriggerType Trigger { get; set; }
public List<Command> Commands { get; set; }
public int CommandIndex { get; set; }
public bool Running { get; set; }
public bool Erased { get; set; }
public Event() { Erased = false; }
public void Update(GameTime gameTime){
if(Erased) return;
if(Running){
// continue command execution
}
else // check for triggering
switch(Trigger){ }
}
public void Draw()[
if(Erased) return;
// drawing code
}
}
The command class and the TriggerType enum should not be an issue.
I hope this helps you get what you wanted. It's a bit hard to tell you exactly how you should do it based on such little information. Good luck.

What is the best way to handle creating, and updating Complex Datatypes in MVC3?

Ok I've been trying to figure out the best way to do this for a few days, but still haven't come up with a very elegant answer so am hoping I someone can point me in the right direction or give some peer review :)
Basically I have 3 classes (they are different and much more complex than these):
public class Person
{
int ID { get; set;}
string Name { get; set; }
virtual IEnumerable<Place> { get; set; }
}
public class Place
{
int ID { get; set;}
string Name { get; set; }
virtual IEnumerable<Thing> { get; set; }
}
public class Thing
{
int ID { get; set;}
string Name { get; set; }
virtual IEnumerable<Place> { get; set; }
virtual int PersonID { get; set; }
}
So basically you have Persons, who have many Places, which can have many Things which can also appear in multiple Places (trying to reduce having to store duplicates of Things) but only for that Person
What is the best way to setup my ViewModel to handle this? Should I just create everything by itself using Ajax and Json (what I've been doing) or is there a way to handle this type of relationship in a ViewModel and single post back to the server?
Currently I'm doing the following:
Fill out Person form -> ajax save to server, get Person ID
Fill out Place form (including Person's ID) -> ajax save to server, get Place ID
Fill out Thing form (including Person ID and Place IDs in a delimited string
I know there should be an easier way to do this as its kinda bulky, but since its all query string I can't figure it out
You say "kinda bulky," but I think it tends to be more lightweight if you can build an object graph on a form in real time by using AJAX/JSON, probably against a RESTful API, somewhat as you describe.
The alternative is using script (jQuery, JSMVC, Knockout) to build a form and POST the whole sucker at once. I've had to do this in some situations where none of the data should be persisted until the whole graph is committed. The trick here is understanding ModelBinder and how it builds/updates that graph for you.
If this is what you were asking, I can expand on the key points of how ModelBinder deals with complex object graphs and collections.
I answered a similar question about how to handle this using interfaces and partial views.
How to create Asp.Net MVC 3 view model

javascript Highcharts object as a C# class

I've been working with javascript Highcharts and I made a basic 'Chart Builder' app. One of my goals is to have the user create and modify as many options as they like and save those to the db. The main problem I'm having is trying to convert the Highcharts object to a c# class. I've been building it slowly(ie manually) with the parts I need, as I need them, but to eventually get the whole thing converted will take a long time.
Ideally, I'd like to create and setup the whole highcharts options object server side and just send it 100% complete to highcharts
Is there any easy way to do this? Has anyone already done this?
Here is the Highcharts reference page: http://www.highcharts.com/ref/
and this is what I've done so far.
public class Highchart
{
public title title { get; set; }
public plotOptions plotOptions { get; set; }
}
public class title
{
public string text { get; set; }
}
public class plotOptions
{
public series series { get; set; }
}
public class series
{
public string stacking { get; set; }
public string borderColor { get; set; }
public bool shadow { get; set; }
public int borderWidth { get; set; }
}
As you can see, I just started ^_^
Update : The Highcharts .Net library has been updated in December, and is nearly feature complete as per V2.1.9 of the Javascript library.
The .Net library currently has support for multiple axes, point objects, viewstate management after postbacks, click events for points, series etc, and a built in implementation of an AJAX datasource ;) You don't need to write a single line of JS code unless you want to handle click events; you simply code in C#, and the appropriate JS is rendered automatically for you..
Click here to view the Live Demo

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