MVC - 3.3 Maybe Monad Example | C# Online Compiler

MVC - 3.3 Maybe Monad Example by dimitrispapadim

using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
///Practical functional programing in C#
//functional programming in modern Web Application development using Asp.Net Core and 
//Domain Driven Design with the language-extfunctional library in C#
//https://leanpub.com/practical-functional-CSharp		
namespace HelloWorldMvcApp
{
	public static partial class FunctionalExtensions
    {
        public static Maybe<T> FirstOrNone<T>(this List<T> @source, Func<T, bool> predicate)
        {
            var firstOrDefault = @source.FirstOrDefault(predicate);
            return firstOrDefault != null ?
                new Some<T>(firstOrDefault) :
                (Maybe<T>)new None<T>();
        }
    }
	
	//----------------------------------------------------------------
	//----------------------View models-------------------------------
	//----------------------------------------------------------------

	public class ClientViewModel
	{
		[Required]
		[MinLength(10)]
		[MaxLength(100)]
		[Display(Name = "Enter Client Id:")]
		public string ClientId { get; set; }

		//See here for list of answers
		public string Name { get; set; }
	}
	
	//----------------------------------------------------------------
	//----------------------   Models  -------------------------------
	//----------------------------------------------------------------
	
	    public class Client
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int EmployeeId { get; set; }
    }
    public class MockClientRepository
    {
        List<Client> clients = new List<Client>{
                    new  Client{Id=1, Name="Jim",  EmployeeId=1},
                    new  Client{Id=2, Name="John", EmployeeId=4}
                };

        public Maybe<Client> GetById(int id){return  clients.FirstOrNone(x => x.Id == id);}

    }
	
	
	public class Employee
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
	
    public class MockEmployeeRepository
    {
        List<Employee> employees =  new List<Employee>{
                    new  Employee{Id=1, Name="Jane"},
                    new  Employee{Id=2, Name="Rick"}
                };


        public Maybe<Employee> GetById(int id){return  employees.FirstOrNone(x => x.Id == id);}


    }

	
	//----------------------------------------------------------------
	//----------------------   Maybe   -------------------------------
	//----------------------------------------------------------------
	
	public abstract class Maybe<T>
    {
        public abstract Maybe<T1> Map<T1>(Func<T, T1> f);

        public abstract T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some);
		       
		public Maybe<T1> Bind<T1>(Func<T, Maybe<T1>> f){
            return this.MatchWith(
                    None: () => new None<T1>(),
                    Some: (v) => f(v)
                 );
			}
    }

    public class None<T> : Maybe<T>
    {
        public None() { }

        public override Maybe<T1> Map<T1>(Func<T, T1> f)
        {
            return new None<T1>();
        }

        public override T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some)
        {
            return None();
        }
    }

    public class Some<T> : Maybe<T>
    {
        private readonly T value;
        public Some(T value) { this.value = value; }

        public override Maybe<T1> Map<T1>(Func<T, T1> f)
        {
            return new Some<T1>(f(this.value));
        }
        public override T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some)
        {
            return Some(this.value);
        }
    }
}

Model

​x
 
using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
///Practical functional programing in C#
//functional programming in modern Web Application development using Asp.Net Core and 
//Domain Driven Design with the language-extfunctional library in C#
//https://leanpub.com/practical-functional-CSharp       
namespace HelloWorldMvcApp
{
    public static partial class FunctionalExtensions
    {
        public static Maybe<T> FirstOrNone<T>(this List<T> @source, Func<T, bool> predicate)
        {
            var firstOrDefault = @source.FirstOrDefault(predicate);
            return firstOrDefault != null ?
                new Some<T>(firstOrDefault) :
                (Maybe<T>)new None<T>();
        }
    }
    
    //----------------------------------------------------------------
    //----------------------View models-------------------------------
    //----------------------------------------------------------------
​
    public class ClientViewModel
    {
        [Required]
        [MinLength(10)]
        [MaxLength(100)]
        [Display(Name = "Enter Client Id:")]
        public string ClientId { get; set; }
​
        //See here for list of answers
        public string Name { get; set; }
    }
    
    //----------------------------------------------------------------
    //----------------------   Models  -------------------------------
    //----------------------------------------------------------------
    
        public class Client
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int EmployeeId { get; set; }
    }
    public class MockClientRepository
    {
        List<Client> clients = new List<Client>{
                    new  Client{Id=1, Name="Jim",  EmployeeId=1},
                    new  Client{Id=2, Name="John", EmployeeId=4}
                };
​
        public Maybe<Client> GetById(int id){return  clients.FirstOrNone(x => x.Id == id);}
​
    }
    
    
    public class Employee
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    
    public class MockEmployeeRepository
    {
        List<Employee> employees =  new List<Employee>{
                    new  Employee{Id=1, Name="Jane"},
                    new  Employee{Id=2, Name="Rick"}
                };
​
​
        public Maybe<Employee> GetById(int id){return  employees.FirstOrNone(x => x.Id == id);}
​
​
    }
​
    
    //----------------------------------------------------------------
    //----------------------   Maybe   -------------------------------
    //----------------------------------------------------------------
    
    public abstract class Maybe<T>
    {
        public abstract Maybe<T1> Map<T1>(Func<T, T1> f);
​
        public abstract T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some);
               
        public Maybe<T1> Bind<T1>(Func<T, Maybe<T1>> f){
            return this.MatchWith(
                    None: () => new None<T1>(),
                    Some: (v) => f(v)
                 );
            }
    }
​
    public class None<T> : Maybe<T>
    {
        public None() { }
​
        public override Maybe<T1> Map<T1>(Func<T, T1> f)
        {
            return new None<T1>();
        }
​
        public override T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some)
        {
            return None();
        }
    }
​
    public class Some<T> : Maybe<T>
    {
        private readonly T value;
        public Some(T value) { this.value = value; }
​
        public override Maybe<T1> Map<T1>(Func<T, T1> f)
        {
            return new Some<T1>(f(this.value));
        }
        public override T1 MatchWith<T1>(Func<T1> None, Func<T, T1> Some)
        {
            return Some(this.value);
        }
    }
}

@model HelloWorldMvcApp.ClientViewModel
@{
	Layout = null;
}

<!DOCTYPE html>
<!-- template from http://getbootstrap.com/getting-started -->

<html lang="en">
	<head>
		<meta charset="utf-8">
		<meta http-equiv="X-UA-Compatible" content="IE=edge">
		<meta name="viewport" content="width=device-width, initial-scale=1">
		<title>Bootstrap 101 Template</title>

		<!-- CSS Includes -->
		<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
		
		<style type="text/css">

			.field-validation-error {
				color: #ff0000;
			}

		</style>
	</head>
	
	<body>

		<div class="container">
			<a target="_blank" href="https://leanpub.com/practical-functional-csharp">Source from  : Practical functional C# </a>

			<div class="col-md-6 col-md-offset-3">
				<h3> 3.3	Maybe Monad Example</h3>
			</br>
				@using (Html.BeginForm())
				{
					<div class="form-group">
						@Html.LabelFor(m => m.ClientId)
						@Html.TextBoxFor(model => model.ClientId, new {@class="form-control"}) 
						@Html.ValidationMessageFor(model => model.ClientId)
					</div>
				
					<button type="button" class="btn btn-success submit">Search</button>
				}
	
				<br/><br/>
				<div class="alert alert-warning fade">
					<strong><span class="alert-content"></span></strong>
				</div>
			</div>
		</div>

		<!-- JS includes -->
		<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
		<script src="//netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>
	
		<script src="//ajax.aspnetcdn.com/ajax/jquery.validate/1.11.1/jquery.validate.min.js"></script>
		<script src="//ajax.aspnetcdn.com/ajax/mvc/4.0/jquery.validate.unobtrusive.min.js"></script>
		
		<script type="text/javascript">
		
			function openAlert(txt) {
				$('.alert-content').text(txt);
				$('.alert').addClass('in');
			}
		
			function closeAlert() {
				$('.alert').removeClass('in');
			}
		
			$(function(){
				var answer = '@Model.Name';
		
				if(answer && answer != '') 
					openAlert(answer);
		
				$('#Question').change(closeAlert);
				$('#Question').keyup(closeAlert);
		
				$('.submit').click(function(){
					if($('form').valid()) {
			        var clientId = $('#ClientId').val();
				    var postUrl = "@Url.RouteUrl(new{ action="GetAssignedEmployeeNameById", controller="Home"})"
			 +`?clientId=${clientId}`;
				   fetch(postUrl,
                        { method: 'POST' })
			            .then(response => response.json())
                        .then((response) => {
                            openAlert(response);
                        })
                        .then((result) => {
                            openAlert(result);

                        });
					}
					else {
						closeAlert();
					}
				});
			
			});

		</script>
	</body>
</html>

View

 
@model HelloWorldMvcApp.ClientViewModel
@{
    Layout = null;
}
​
<!DOCTYPE html>
<!-- template from http://getbootstrap.com/getting-started -->
​
<html lang="en">
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>Bootstrap 101 Template</title>
​
        <!-- CSS Includes -->
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
        
        <style type="text/css">
​
            .field-validation-error {
                color: #ff0000;
            }
​
        </style>
    </head>
    
    <body>
​
        <div class="container">
            <a target="_blank" href="https://leanpub.com/practical-functional-csharp">Source from  : Practical functional C# </a>
​
            <div class="col-md-6 col-md-offset-3">
                <h3> 3.3    Maybe Monad Example</h3>
            </br>
                @using (Html.BeginForm())
                {
                    <div class="form-group">
                        @Html.LabelFor(m => m.ClientId)
                        @Html.TextBoxFor(model => model.ClientId, new {@class="form-control"}) 
                        @Html.ValidationMessageFor(model => model.ClientId)
                    </div>
                
                    <button type="button" class="btn btn-success submit">Search</button>
                }
    
                <br/><br/>
                <div class="alert alert-warning fade">
                    <strong><span class="alert-content"></span></strong>
                </div>
            </div>
        </div>
​
        <!-- JS includes -->
        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
        <script src="//netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>
    
        <script src="//ajax.aspnetcdn.com/ajax/jquery.validate/1.11.1/jquery.validate.min.js"></script>
        <script src="//ajax.aspnetcdn.com/ajax/mvc/4.0/jquery.validate.unobtrusive.min.js"></script>
        
        <script type="text/javascript">
        
            function openAlert(txt) {
                $('.alert-content').text(txt);
                $('.alert').addClass('in');
            }
        
            function closeAlert() {
                $('.alert').removeClass('in');
            }
        
            $(function(){
                var answer = '@Model.Name';
        
                if(answer && answer != '') 
                    openAlert(answer);
        
                $('#Question').change(closeAlert);
                $('#Question').keyup(closeAlert);
        
                $('.submit').click(function(){
                    if($('form').valid()) {
                    var clientId = $('#ClientId').val();
                    var postUrl = "@Url.RouteUrl(new{ action="GetAssignedEmployeeNameById", controller="Home"})"
             +`?clientId=${clientId}`;
                   fetch(postUrl,
                        { method: 'POST' })
                        .then(response => response.json())
                        .then((response) => {
                            openAlert(response);
                        })
                        .then((result) => {
                            openAlert(result);
​
                        });
                    }
                    else {
                        closeAlert();
                    }
                });
            
            });
​
        </script>
    </body>
</html>
​

using System;
using System.Web.Mvc;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;


namespace HelloWorldMvcApp
{
	public class HomeController : Controller
	{
	    MockClientRepository Clients = new MockClientRepository();
        MockEmployeeRepository Employees = new MockEmployeeRepository();
		
		[HttpGet]
		public ActionResult Index()
		{
			return View(new ClientViewModel());
		}


		[HttpPost]
		public  JsonResult GetAssignedEmployeeNameById(int clientId)
		{		
			string assignedEmployeeName =  
			  Clients
                .GetById(clientId)
                .Map(client => client.EmployeeId)
                .Bind(Employees.GetById)
                .MatchWith<string>(
				   Some: (employee) => employee.Name,
                   None: () => "there is no employee");

			return Json(assignedEmployeeName);
		}

	}
	
}

Controller

 
using System;
using System.Web.Mvc;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
​
​
namespace HelloWorldMvcApp
{
    public class HomeController : Controller
    {
        MockClientRepository Clients = new MockClientRepository();
        MockEmployeeRepository Employees = new MockEmployeeRepository();
        
        [HttpGet]
        public ActionResult Index()
        {
            return View(new ClientViewModel());
        }
​
​
        [HttpPost]
        public  JsonResult GetAssignedEmployeeNameById(int clientId)
        {       
            string assignedEmployeeName =  
              Clients
                .GetById(clientId)
                .Map(client => client.EmployeeId)
                .Bind(Employees.GetById)
                .MatchWith<string>(
                   Some: (employee) => employee.Name,
                   None: () => "there is no employee");
​
            return Json(assignedEmployeeName);
        }
​
    }
    
}

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