DOTS - System

using System;
using System.Linq;

/*Luhn validates and creates checksum codes*/
public class Luhn {
	private int[] Code;

	/*Luhn creates a new checksum number*/
	public Luhn(long code) {
		Code = code.ToString ()
			.ToArray()
			.Select (d => (int)(d - '0'))
			.ToArray();
	}

	/*CheckDigit returns the last number*/
	public int CheckDigit {
		get { return Code.Last(); }
	}

	/*Addends doubles every other number starting from the right
	and subtracts 9 if the result is 10 or greater*/
	public int[] Addends {
		get {
			int[] doubled = (int[])Code.Clone();
			for (int i = doubled.Length - 2; 0 <= i; i -= 2) {
				doubled [i] *= 2;
				if (10 <= doubled [i])
					doubled[i] -= 9;
			}
			return doubled;
		}
	}

	/*Checksum sums all the digits after adding the ends*/
	public int Checksum {
		get { return Addends
				.Aggregate (0, (total, n) => total + n);
			}
	}

	/*Valid is true when the code is valid*/
	public bool Valid {
		get { return (Checksum % 10) == 0; }
	}

	/*Create adds a check digit to make the code valid*/
	public static long Create(long code) {
		code *= 10;
		Luhn luhn = new Luhn (code);
		if (luhn.Valid)
			return code;
		return code + (10 - (luhn.Checksum % 10));
	}
}

using System;
using System.Diagnostics.CodeAnalysis;

public class Clock : IEquatable<Clock>
{
    private int _hour;
    private int _minute;

    public Clock(int hours, int minutes)
    {
        _hour = (hours                                    // just take the given hours and
            + minutes / 60                                // add full hours of minutes if we have more than 60
                                                          // minutes
            - (minutes < 0 && minutes % 60 != 0 ? 1 : 0)  // but the part of negative minutes that is not an full
                                                          // hour subtracts one hour, e.g. 01:-10 means (00:50)
            ) % 24;                                       // at last, ensure hours roll over when longer as a day

        if (_hour < 0) _hour += 24;      // finally avoid negative hours: e.g. -3 means 21 (3 hours befor midnight)

        _minute = minutes % 60;          // just take the minutes, but to ensure they roll over when longer as an
                                         // hour, contribution to the hour was already added above
        if (_minute < 0) _minute += 60;  // e.g. -10 means 50 (10 minutes befor the next full hour)
    }

    public Clock Add(int minutesToAdd) => new Clock(_hour, _minute + minutesToAdd);

    public Clock Subtract(int minutesToSubtract) => new Clock(_hour, _minute - minutesToSubtract);

    public override string ToString() => $"{_hour:00}:{_minute:00}";

    public bool Equals([AllowNull] Clock other)
    {
        if (other == null)
            return false;
        if (this == other)
            return true;
        return _hour == other._hour && _minute == other._minute;
    }

    // these methods are not needed to make the tests running but it is recommended to override Equals(object) and
    // GetHashCode() when implementing IEquatable
    public override bool Equals(object obj) => Equals(obj as Clock);
    public override int GetHashCode() => _hour * 60 + _minute;
}

RaycastHit hit;
Ray ray = camera.ScreenPointToRay(Input.mousePosition);

if (Physics.Raycast(ray, out hit)) {
  Transform objectHit = hit.transform;

  // Do something with the object that was hit by the raycast.
}

using ConsumingWebAapiRESTinMVC.Models;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using System.Web.Mvc;

namespace ConsumingWebAapiRESTinMVC.Controllers
{
    public class HomeController : Controller
    {
        //Hosted web API REST Service base url
        string Baseurl = "http://192.168.95.1:5555/";
        public async Task<ActionResult> Index()
        {
            List<Employee> EmpInfo = new List<Employee>();
            using (var client = new HttpClient())
            {
                //Passing service base url
                client.BaseAddress = new Uri(Baseurl);
                client.DefaultRequestHeaders.Clear();
                //Define request data format
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                //Sending request to find web api REST service resource GetAllEmployees using HttpClient
                HttpResponseMessage Res = await client.GetAsync("api/Employee/GetAllEmployees");
                //Checking the response is successful or not which is sent using HttpClient
                if (Res.IsSuccessStatusCode)
                {
                    //Storing the response details recieved from web api
                    var EmpResponse = Res.Content.ReadAsStringAsync().Result;
                    //Deserializing the response recieved from web api and storing into the Employee list
                    EmpInfo = JsonConvert.DeserializeObject<List<Employee>>(EmpResponse);
                }
                //returning the employee list to view
                return View(EmpInfo);
            }
        }
    }
}

using System;
class RemoveCharacter {
  static void Main() {
    string s = "king";
    string result = s.Remove(s.Length-1);
    Console.WriteLine(result);
  }
}

namespace FetchAppsettingsValue.Controllers
{
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Extensions.Configuration;
    using System.Collections.Generic;

    [Route("api/Configuration")]
    [ApiController]
    public class ConfigurationController : ControllerBase
    {
        private readonly IConfiguration _config;

        public ConfigurationController(IConfiguration config)
        {
            _config = config;
        }

        // GET: api/Configuration
        [HttpGet]
        public IEnumerable<string> Get()
        {
            var result = _config.GetValue<string>("Logging:LogLevel:Default"); // "Information"
            return new string[] { result.ToString() };
        }
    }
}

//AppSettings.cs
namespace FetchAppsettingsValue
{
    public class AppSettings
    {
        public Logging Logging { get; set; }
        public string AllowedHosts { get; set; }
    }

    public class Logging
    {
        public LogLevel LogLevel { get; set; }
    }

    public class LogLevel
    {
        public string Default { get; set; }

        public string Warning { get; set; }

        public string Error { get; set; }
    }
}

public void ConfigureServices(IServiceCollection services)
{
    services.Configure<Logging>(Configuration.GetSection("Logging"));

    services.AddControllers();
}

namespace FetchAppsettingsValue.Controllers
{
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Extensions.Options;
    using System.Collections.Generic;

    [Route("api/Option")]
    [ApiController]
    public class OptionController : ControllerBase
    {
        private readonly IOptions<Logging> _logging;
        public OptionController(IOptions<Logging> logging)
        {
            _logging = logging;
        }

        // GET: api/Option
        [HttpGet]
        public IEnumerable<string> Get()
        {
            var result = _logging.Value.LogLevel.Default; // "Information"

            return new string[] { result };
        }
    }
}

namespace FetchAppsettingsValue.Controllers
{
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Extensions.Options;
    using System.Collections.Generic;

    [Route("api/Option")]
    [ApiController]
    public class OptionController : ControllerBase
    {
        private readonly IOptions<Logging> _logging;
        public OptionController(IOptions<Logging> logging)
        {
            _logging = logging;
        }

        // GET: api/Option
        [HttpGet]
        public IEnumerable<string> Get()
        {
            var result = _logging.Value.LogLevel.Default; // "Information"

            return new string[] { result };
        }
    }
}

[HttpPost]
public ActionResult Transfer()
{
    try
    {
        /// Make a transfer
    }
    catch (OutOfCreditException ex)
    {
        var problemDetails = new ProblemDetails
        {
            Status = StatusCodes.Status403Forbidden,
            Type = "https://example.com/probs/out-of-credit",
            Title = "You do not have enough credit.",
            Detail = "Your current balance is 30, but that costs 50.",
            Instance = HttpContext.Request.Path
        };

        return new ObjectResult(problemDetails)
        {
            ContentTypes = { "application/problem+json" },
            StatusCode = 403,
        };
    }

    return Ok();
}

[HttpPost]
public ActionResult Transfer(TransferInfo model)
{
    if (!ModelState.IsValid)
    {
        var problemDetails = new ValidationProblemDetails(ModelState);

        return new ObjectResult(problemDetails)
        {
            ContentTypes = { "application/problem+json" },
            StatusCode = 403,
        };
    }

    return Ok();
}

public void ConfigureServices(IServiceCollection services)
{
    services
        .AddMvc()
        .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

    services.Configure<ApiBehaviorOptions>(options =>
    {
        options.InvalidModelStateResponseFactory = context =>
        {
            var problemDetails = new ValidationProblemDetails(context.ModelState)
            {
                Instance = context.HttpContext.Request.Path,
                Status = StatusCodes.Status400BadRequest,
                Type = $"https://httpstatuses.com/400",
                Detail = ApiConstants.Messages.ModelStateValidation
            };
            return new BadRequestObjectResult(problemDetails)
            {
                ContentTypes =
                {
                    ApiConstants.ContentTypes.ProblemJson,
                    ApiConstants.ContentTypes.ProblemXml
                }
            };
        };
    });
}

public void ConfigureServices(IServiceCollection services)
{
    services
        .AddProblemDetails(setup =>
        {
            setup.IncludeExceptionDetails = _ => Environment.IsDevelopment();
        })

    ...
}

[HttpPost]
public ActionResult Transfer(TransferInfo model)
{
    throw new OutOfCreditException(
        "You do not have enough credit.",
        balance: 30,
        cost: 50);

    return Ok();
}