Create Observable for Streaming Class in Net Core

Question

How do I create an Observable for a class? Eg here is class for continuous sales

public class Product
{
     public int ProductId {get;set;}
     public string ProductDescription {get;set;}
     public float Sales{get;set;}
}

How to create Observable? Say they are coming into a List<Product> with Add(), products keep getting added representing transactions.

Anytime, a product is added anywhere in Console program, the subscriber will observe it.

var productSample1 = new Product { ProductId = 1, ProductDescription = "Furniture" };
var productSample2 = new Product { ProductId = 2, ProductDescription = "Book" };
var productSample3 = new Product { ProductId = 3, ProductDescription = "car" };

var productlist = new List<Product>();
productlist.Add(productSample1);
....
productlist.Add(productSample2);
...
productlist.Add(productSample3);

Maybe something like this,

var products = Observable.FromEventPattern < EventHandler<Product>, Product>();

Trying to read resources below, trying to add on ,

Generate numbers at random time intervals with rx

Intro to Rx

what is the lifetime of your generator (how Products are incoming)? It's not that easy to answer. It could be a cold/hot observable, Observable.FromEventPattern/ Observable.Create/ ... — ntohl, Oct 09 '19 at 07:04
hi @ntohl say 20 products a minute, it can be a hot observable — , Oct 09 '19 at 07:13
How does your generation look like? Where is the code, where the `new Product` would be? Or that is what you like to delegate to Observable? — ntohl, Oct 09 '19 at 10:26

Paulo Morgado · Accepted Answer · 2019-10-09T15:56:51.283

0

You can either use an ObservableCollection:

var list = new ObservableCollection<int>();
using (var o = Observable
    .FromEventPattern<NotifyCollectionChangedEventHandler, NotifyCollectionChangedEventArgs>(h => list.CollectionChanged += h, h => list.CollectionChanged -= h)
    .Subscribe(e => Console.WriteLine($"{e.EventArgs.Action} {e.EventArgs.NewItems[0]}")))
{
    list.Add(1);
    list.Add(10);
}

// Add 1
// Add 10

Or turn it around and add from a subscription:

var list = new List<int>();
var subject = new Subject<int>();
using (var o = subject.Subscribe(i => list.Add(i)))
{
    subject.OnNext(1);
    subject.OnNext(10);
}

foreach (var i in list)
{
    Console.WriteLine(i);
}

// 1
// 10

edited Oct 09 '19 at 15:56

answered Oct 09 '19 at 08:51

Paulo Morgado

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Thanks, and anytime I run the statement, list.Add(productSample3), or, list.Add(productSample4), or list.Add(productSample5), in another totally separate statements, it will, automatically read into Observable? – Oct 09 '19 at 15:06
also, another question here, https://stackoverflow.com/questions/58296396/entity-framework-convert-changetracker-to-observable-with-reactive-stream?noredirect=1&lq=1 – Oct 09 '19 at 15:08
@earlwatkins85, what do you mean by "automatically read into Observable"? – Paulo Morgado Oct 09 '19 at 15:57
I described more in question, also; why did we get rid of Product and replace with int, trying to specify answer to question for custom class, thanks – Oct 09 '19 at 16:16
The item type doesn't matter. This answer is valid for any item type and has the corresponding console output in the comments. – Paulo Morgado Oct 09 '19 at 18:15

Create Observable for Streaming Class in Net Core

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