RavenDB just rocked my world. It’s extremely approachable, even for non-database guys – it took me less than 30 minutes to get up and running

 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

{
    "dependencies": {
         //same as before
         "Microsoft.AspNetCore.Mvc.TagHelpers": "1.0.0",
         "Microsoft.AspNetCore.Razor.Runtime": "1.0.0",
         "Microsoft.AspNetCore.Razor.Tools": {
            "version": "1.0.0-preview2-final",
            "type": "build"
        }
    },
 
    "tools": {
         //same as before
        "Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final"
    } 
}

 <a asp-controller="Home" asp-action="Index" asp-route-id="123">Home</a>

 <a asp-route="login">Login</a>

 <a asp-controller="Account"
   asp-action="Register"
   asp-protocol="https"
   asp-host="asepecificdomain.com"
   asp-fragment="fragment">Register</a>

 <form asp-controller="Account"
      asp-action="Login"
      asp-route-returnurl="@ViewBag.ReturnUrl"
      method="post" >
</form>

 <form action="/Account/Login?returnurl=%2FHome%2FAbout" method="post">

 <form asp-route="login"
      asp-route-returnurl="@ViewBag.ReturnUrl"
      method="post" >
</form>

 <script asp-src-include="~/app/**/*.js"></script>

 <script src="/app/app.js"></script>
<script src="/app/controllers/controller1.js"></script>
<script src="/app/controllers/controller2.js"></script>
<script src="/app/controllers/controller3.js"></script>
<script src="/app/controllers/controller4.js"></script>
<script src="/app/services/service1.js"></script>
<script src="/app/services/service2.js"></script>

 <script asp-src-include="~/app/**/*.js"
        asp-src-exclude="~/app/services/**/*.js">
</script>

 <link rel="stylesheet" href="//ajax.aspnetcdn.com/ajax/bootstrap/3.0.0/css/bootstrap.min.css"
      asp-fallback-href="~/lib/bootstrap/css/bootstrap.min.css"
      asp-fallback-test-class="hidden"
      asp-fallback-test-property="visibility"
      asp-fallback-test-value="hidden" />
 
<script src="//ajax.aspnetcdn.com/ajax/bootstrap/3.0.0/bootstrap.min.js"
        asp-fallback-src="~/lib/bootstrap/js/bootstrap.min.js"
        asp-fallback-test="window.jQuery">
</script>

 <link rel="stylesheet" href="~/css/site.min.css" asp-file-version="true"/>

 <link rel="stylesheet" href="/css/site.min.css?v=UdxKHVNJA5vb1EsG9O9uURFDfEE3j1E3DgwL6NiDGMc" />

 <img src="~/images/logo.png"
     alt="company logo"
     asp-file-version="true" />

 <img src="/images/logo.png?v=W2F5D366_nQ2fQqUk3URdgWy2ZekXjHzHJaY5yaiOOk"
     alt="company logo"/>

<environment names="Development">    
   <link rel="stylesheet" href="~/css/site1.css" />
   <link rel="stylesheet" href="~/css/site2.css" />
</environment>

<environment names="Staging,Production">
   <link rel="stylesheet" href="~/css/site.min.css" asp-file-version="true"/>
</environment>

public class CustomerViewModel
{
   public string Vehicle { get; set; }  
   public List<SelectListItem> Vehicles { get; set; }

 <select asp-for="Vehicle" asp-items="Model.Vehicles">
</select>

[DataContract(IsReference = true)]
public class Post
{
    public Post()
    {
        comments = new HashSet<Comments>();
    }
    
    [DataMember]
    public int PostId { get; set; }
    [DataMember]
    public string Title { get; set; }
    [DataMember]
    public virtual ICollection<Comment> Comments { get; set; }
}

[DataContract(IsReference=true)]
public class Comment
{
    [DataMember]
    public int CommentId { get; set; }
    [DataMember]
    public int PostId { get; set; }
    [DataMember]
    public string CommentText { get; set; }
    [DataMember]
    public virtual Post Post { get; set; }
}

public class EFRecipesEntities : DbContext
{
    public EFRecipesEntities() : base("name=EFRecipesEntities") {}

    public DbSet<Post> posts;
    public DbSet<Comment> comments;
}

<connectionStrings>
  <add name="Recipe2ConnectionString"
    connectionString="Data Source=.;
    Initial Catalog=EFRecipes;
    Integrated Security=True;
    MultipleActiveResultSets=True"
    providerName="System.Data.SqlClient" />
</connectionStrings>

[ServiceContract]
public interface IService1
{
    [OperationContract]
    void Cleanup();
    [OperationContract]
    Post GetPostByTitle(string title);
    [OperationContract]
    Post SubmitPost(Post post);
    [OperationContract]
    Comment SubmitComment(Comment comment);
    [OperationContract]
    void DeleteComment(Comment comment);
}

class Program
{
    static void Main(string[] args)
    {
        using (var client = new ServiceReference2.Service1Client())
        {
            // cleanup previous data
            client.Cleanup();
            // insert a post
            var post = new Post { Title = "POCO Proxies" };
            post = client.SubmitPost(post);
            // update the post
            post.Title = "Change Tracking Proxies";
            client.SubmitPost(post);
            // add a comment
            var comment1 = new Comment { CommentText = "Virtual Properties are cool!", PostId = post.PostId };
            var comment2 = new Comment { CommentText = "I use ICollection<T> all the time", PostId = post.PostId };
            comment1 = client.SubmitComment(comment1);
            comment2 = client.SubmitComment(comment2);
            // update a comment
            comment1.CommentText = "How do I use ICollection<T>?";
            client.SubmitComment(comment1);
            // delete comment 1
            client.DeleteComment(comment1);
            // get posts with comments
            var p = client.GetPostByTitle("Change Tracking Proxies");
            Console.WriteLine("Comments for post: {0}", p.Title);
            foreach (var comment in p.Comments)
            {
                Console.WriteLine("\tComment: {0}", comment.CommentText);
            }
        }
    }
}

#1 let mutable phrase = "Can it change? "

#2 printfn "%s" phrase

#3 phrase <- "yes, it can."

#4 printfn "%s" phrase

Can it change?  
yes, it can.

#1 let mutable phrase = "Can it change?  "

#3 phrase <- 1

Prog.fs(9,10): error: FS0001: This expression has type
int
but is here used with type
string

let redefineX() =
let x = "One"
printfn "Redefining:\r\nx = %s" x
if true then
   let x = "Two"
printfn "x = %s" x
printfn "x = %s" x

Redefining:
x = One
x = Two
x = One

let mutableX() =
let mutable x = "One"
printfn "Mutating:\r\nx = %s" x
if true then
   x <- "Two"
printfn "x = %s" x
printfn "x = %s" x

Mutating:
x = One
x = Two
x = Two

let refVar = ref 6

refVar := 50



printfn "%d" !refVar

let xRef : int ref = ref 10

printfn "%d" (xRef.Value)
printfn "%d" (xRef.contents)

xRef.Value <- 11
printfn "%d" (xRef.Value)
xRef.contents <- 12
printfn "%d" (xRef.contents)

10
10
11
12 

let keepIfPositive (a : int) = if a > 0 then Some(a) else None

let exists (x : int option) = 
    match x with
    | Some(x) -> true
    | None -> false

let rec tryFindMatch pred list =
    match list with
    | head :: tail -> if pred(head)
                        then Some(head)
                        else tryFindMatch pred tail
    | [] -> None

let result1 = tryFindMatch (fun elem -> elem = 100) [ 200; 100; 50; 25 ] //برابر با 100 است

let result2 = tryFindMatch (fun elem -> elem = 26) [ 200; 100; 50; 25 ]// برابر با None است

open System.IO
let openFile filename =
    try 
        let file = File.Open (filename, FileMode.Create)
        Some(file)
    with
        | ex -> eprintf "An exception occurred with message %s" ex.Message
                None

type enum-name =
   | value1 = integer-literal1
   | value2 = integer-literal2
   ...

type Color =
   | Red = 0
   | Green = 1
   | Blue = 2

let col1 : Color = Color.Red

type uColor =
   | Red = 0u
   | Green = 1u
   | Blue = 2u
let col3 = Microsoft.FSharp.Core.LanguagePrimitives.EnumOfValue<uint32, uColor>(2u)

using(var writer = new StreamWriter(filePath))
{
   
}

let writeToFile fileName =
    use sw = new System.IO.StreamWriter(fileName : string)
    sw.Write("Hello ")

[<Measure>] type unit-name [ = measure ]

[<Measure>] type cm

[<Measure>] type ml = cm^3

let value = 1.0<cm>

[<Measure>] type g                 تعریف واحد گرم
[<Measure>] type kg               تعریف واحد کیلوگرم
let gramsPerKilogram : float<g kg^-1> = 1000.0<g/kg>    تعریف تابع تبدیل

[<Measure>] type degC // دما بر حسب سلسیوس
[<Measure>] type degF // دما بر حسب فارنهایت

let convertCtoF ( temp : float<degC> ) = 9.0<degF> / 5.0<degC> * temp + 32.0<degF> // تابع تبدیل سلسیوس به فارنهایت
let convertFtoC ( temp: float<degF> ) = 5.0<degC> / 9.0<degF> * ( temp - 32.0<degF>) // تابع تبدیل فارنهایت به سلسیوس

let degreesFahrenheit temp = temp * 1.0<degF> // درجه به فارنهایت
let degreesCelsius temp = temp * 1.0<degC> // درجه به سلسیوس

printfn "Enter a temperature in degrees Fahrenheit." 
let input = System.Console.ReadLine()
let mutable floatValue = 0.
if System.Double.TryParse(input, &floatValue)// اگر ورودی عدد بود
   then 
      printfn "That temperature in Celsius is %8.2f degrees C." ((convertFtoC (degreesFahrenheit floatValue))/(1.0<degC>))
   else
      printfn "Error parsing input."

Enter a temperature in degrees Fahrenheit.
90
That temperature in degrees Celsius is    32.22.

public void Configure(ILoggerFactory loggerFactory, IApplicationBuilder app, IHostingEnvironment env)
{
   loggerFactory.AddConsole(Configuration.GetSection("Logging"));
   loggerFactory.AddDebug();

{
    "Logging": {
        "IncludeScopes": false,
        "LogLevel": {
            "Default": "Debug",
            "System": "Information",
            "Microsoft": "Information"
        }
    }
}

{
    "dependencies": {
        //same as before 
        "Microsoft.Extensions.Logging": "1.0.0",
        "Microsoft.Extensions.Logging.Console": "1.0.0",
        "Microsoft.Extensions.Logging.Debug": "1.0.0" 
    }
}

[Route("[controller]")]
public class AboutController : Controller
{
    private readonly ILogger<AboutController> _logger;
 
    public AboutController(ILogger<AboutController> logger)
    {
        _logger = logger;
    }
 
    [Route("")]
    public ActionResult Hello()
    {
        _logger.LogInformation("Running Hello");
        return Content("Hello from DNT!");
    }

 loggerFactory.AddDebug(minLevel: LogLevel.Information);

  public enum LogLevel
  {
    Trace,
    Debug,
    Information,
    Warning,
    Error,
    Critical,
    None,
  }