RG.System.Collections.Generic.One 1.0.2

Release Note

Version 1.0.2

1. Moved LINQ methods out of One<T> into a new class Qlosure<T>.
2. Renamed One.Of() to One.Value()
3. Removed object extension method obj.ToOne()
4. Removed IEnumerable extension method obj.AsOne()
5. Removed Join clause

What is One<T>?

One<T> is a generic collection that contains exactly one item. This kind of generic collection allows you to use LINQ expression to write closures and functional programming.

Installation

Using Package Manager Console

Install-Package RG.System.Collections.Generic.One

Using dotnet CLI

dotnet add package RG.System.Collections.Generic.One

Usage

Include using directive

using System.Collections.Generic;

Create instance of One<T>

// using constructor
var oneInt = new One<int>(1);

// using factory
var oneDecimal = One.Value(100.0m);

Use it in LINQ expression as a closure

decimal total = from price in One.Value(199m)
                let quantity = 2m
                let subtotal = price * quantity
                let tax = subtotal * 0.1m
                let discount = 10m
                select subtotal + tax - discount;

Qlosure: Closures Written in LINQ

You can write closures in LINQ by enumerating from a One<T> or a Qlosure<T>.

Start a qlosure

from x in One.Value(e).ToQlosure() // ToQlosure is optional

Introduce a new range variable

from x in One.Value(e)
let y = 10

Introduce a new range variable from another One<T>

from x in One.Value(e)
from y in one // one is a One<int>, z is an Int32

Implicitly cast qlosure to its final value

int result = from x in One.Value(e)
             let y = x * x
             select y;

Auto Disposing Range Variables

All disposable range variables are automatically disposed before stepping into next statement.

string ComputeSecretProof(string accessToken) {
    string secretProof = from appSecret in One.Value(Configuration["AppSecret"])
                         let appSecretBytes = Encoding.UTF8.GetBytes(appSecret)
                         let accessTokenBytes = Encoding.UTF8.GetBytes(accessToken)
                         let hmacssha256 = new HMACSHA256(appSecretBytes)
                         let proofBytes = hmacsha256.ComputeHash(accessTokenBytes)
                         select string.Join("", proofBytes.Select(b => b.ToString("x2")));
    // hmacsha256 already disposed at this point
    return secretProof;
}
                     

Disabling Auto Dispose

string json = from client in One.Value(httpClient).DoNotDisposeValue()
              let uri = new Uri(uriString)
              select client.GetString(uri);
// httpClient is not disposed and can still be reused

Planned Features

1. Full Support for .Net Core 3.0 Nullability
2. Task Chaining

Person person = await from response in httpClient.GetAsync(uri)
                      from json in response.Content.ReadAsStringAsync()
                      select JsonConvert<Person>(json);

Please submit an issue if you need to report bugs or request a feature.