Beefeater - Guard your methods' Ins and Outs. 

public Result<bool, ErrorResult> Create(NotNull<string> filePath, Option<string> second)

Open source MVVM framework for ASP.NET Core and OWIN 

View

@viewModel DotvvmDemo.CalculatorViewModel, Dotvvm
    
<p>
    Enter the first number: 
    <dot:TextBox Text="{value: Number1}" />
</p>
<p>
    Enter the second number: 
    <dot:TextBox Text="{value: Number2}" />
</p>
<p>
    <dot:Button Text="Calculate" Click="{command: Calculate()}" />
</p>
<p>
    The result is: {{value: Result}}
</p>

ViewModel

using System;
    
namespace DotvvmDemo 
{
    public class CalculatorViewModel 
    {
            
        public int Number1 { get; set; }
            
        public int Number2 { get; set; }
            
        public int Result { get; set; }
            
        public void Calculate() 
        {
            Result = Number1 + Number2;
        }
    }
}

var integerArray = new int[3];
var lastItem = integerArray[integerArray.Length - 1];

var integerList = integerArray.ToList();
integerList.Last();

var secondToLast = integerArray[integerArray.Length - 2];

var lastItem = integerArray[^1];

var words = new string[]
{
                // index from start    index from end
    "The",      // 0                   ^9
    "quick",    // 1                   ^8
    "brown",    // 2                   ^7
    "fox",      // 3                   ^6
    "jumped",   // 4                   ^5
    "over",     // 5                   ^4
    "the",      // 6                   ^3
    "lazy",     // 7                   ^2
    "dog"       // 8                   ^1
};              // 9 (or words.Length) ^0

Console.WriteLine($"The last word is {words[words.Length - 1]}");

var index = new Index(value: 1, fromEnd: true);
Index indexStruct = ^1;
var indexShortHand = ^1;

int[] a = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
Console.WriteLine(a[a.Length – 2]); // will write 8 on console.
Console.WriteLine(a[^2]); // will write 8 on console.

Index i5 = 5;
Console.WriteLine(a[i5]);        //will write 5 on console.

Index i2fromEnd = ^2;
Console.WriteLine(a[i2fromEnd]); // will write 8 on console.

var numbers = Enumerable.Range(1, 10).ToArray();

var (start, end) = (1, 7); 
var length = end - start; 

// Using LINQ 
var subset1 = numbers.Skip(start).Take(length);
 
// Or using Array.Copy 
var subset2 = new int[length];
Array.Copy(numbers, start, subset2, 0, length);

var myArray = new string[] { "Item1", "Item2", "Item3", "Item4", "Item5" };

 var fromIndexToX = myArray[1..3]; // = [Item2, Item3]

var fromIndexToXFromTheEnd = myArray[1..^1]; // = [ "Item2", "Item3", "Item4" ]

var fromAnIndexToTheEnd = myArray[1..]; // = [ "Item2", "Item3", "Item4", "Item5" ]

 var fromTheStartToAnIndex = myArray[..3]; // = [ "Item1", "Item2", "Item3" ]

 var entireRange = myArray[..]; // = [ "Item1", "Item2", "Item3", "Item4", "Item5" ]

var myArray = new string[] { "Item1", "Item2", "Item3", "Item4", "Item5" };
for (int i = 1; i <= 3; i++)
{
  Console.WriteLine(myArray[i]);
}

foreach (var item in myArray[1..4]) // = [ "Item2", "Item3", "Item4" ]
{
  Console.WriteLine(item);
}

using System;
using System.Linq;

namespace ConsoleApp
{
    class Program
    {
        private static readonly int[] _numbers = Enumerable.Range(1, 10).ToArray();

        static void Main()
        {
            var skip2CharactersAndTake2Characters = _numbers[2..4]; // صرفنظر کردن از دو عنصر اول و سپس انتخاب دو عنصر
            var skipFirstAndLastCharacter = _numbers[1..^1]; // صرفنظر کردن از دو عنصر اول و آخر
            var last3Characters = _numbers[^3..]; // انتخاب بازه‌ای شامل سه عنصر آخر
            var first4Characters = _numbers[0..4]; // دریافت بازه‌ای از 4 عنصر اول
            var rangeStartFrom2 = _numbers[2..]; // دریافت بازه‌ای شروع شده از المان دوم تا آخر
            var skipLast3Characters = _numbers[..^3]; // صرفنظر کردن از سه المان آخر
            var rangeAll = _numbers[..]; // انتخاب کل بازه
        }
    }
}

var range = new Range(1, 4);
Range rangeStruct = 1..4;
var rangeShortHand = 1..4;

using System;
using System.Linq;

namespace ConsoleApp
{
    class Program
    {
        private static readonly int[] _numbers = Enumerable.Range(1, 10).ToArray();
        static void Print(Range range) => Console.WriteLine($"{range} => {string.Join(", ", _numbers[range])}");

        static void Main()
        {
            Print(1..3); // 1..3 => 2, 3
            Print(..3);      // 0..3 => 1, 2, 3
            Print(3..);      // 3..^0 => 4, 5, 6, 7, 8, 9, 10
            Print(1..^1);    // 1..^1 => 2, 3, 4, 5, 6, 7, 8, 9
            Print(^2..^1);   // ^2..^1 => 9
        }
    }
}

Console.WriteLine("123456789"[1..4]); // Would output 234

var helloWorldStr = "Hello, World!";

var hello = helloWorldStr[..5];
Console.WriteLine(hello); // Output: Hello

var world = helloWorldStr[7..];
Console.WriteLine(world); // Output: World!

var world2 = helloWorldStr[^6..]; // Take the last 6 characters
Console.WriteLine(world); // Output: World!

var arr = (new[] { 1, 4, 8, 11, 19, 31 }).AsSpan();
var range = arr[2..5];

ref int elt1 = ref range[1];
elt1 = -1;

int copiedElement = range[2];
copiedElement = -2;

Console.WriteLine($"range[1]: {range[1]}, range[2]: {range[2]}"); // output: range[1]: -1, range[2]: 19
Console.WriteLine($"arr[3]: {arr[3]}, arr[4]: {arr[4]}"); // output: arr[3]: -1, arr[4]: 19

[PersistJobDataAfterExecution]
   [DisallowConcurrentExecution]
   public class SendGroupEmailJob : IJobBase
   {
       private List<MailAddress> lstMails;
 
       public void Execute(IJobExecutionContext context)
       {
           int result = 0;
           if (context.JobDetail.JobDataMap["UserEmailList"] != null)
           {
               lstMails = context.JobDetail.JobDataMap["UserEmailList"] as List<MailAddress>;
 
               if (lstMails.Count == 0)
               {
 
                   context.Scheduler.UnscheduleJob(new TriggerKey(context.Trigger.Key.Name));
 
 
               }
               else
               {
 
                   JobDataMap map = context.JobDetail.JobDataMap;
                   result = EmailHandler.Send(lstMails[0],
                       map.GetString("Subject"),
                      map.GetString("Body").Replace("[FullName]", lstMails[0].DisplayName).Replace("[Email]", lstMails[0].Address),
                     context.JobDetail.JobDataMap["Attachment"] as List<string>,
                        MailPriority.High,
                        true,
                        Encoding.UTF8,
                        DeliveryNotificationOptions.None,
                        map.GetString("SenderEmail"),
                        map.GetString("SenderName"),
                        map.GetString("BccEmail"),
                        map.GetString("Prefix"),
                        map.GetBoolean("IsSSL"),
                        map.GetBoolean("IsCredential"),
                        map.GetString("Server"),
                        map.GetInt("Port"),
                        map.GetInt("TimeOut"),
                        map.GetString("PassWord"));
                   lstMails.RemoveAt(0);
 
               }
 
 
           }
 
       }
   }

using System.Web;
using System.Windows.Forms;

namespace PdfReportSamples
{
    public static class AppPath
    {
        public static string ApplicationPath
        {
            get
            {
                if (isInWeb)
                    return HttpRuntime.AppDomainAppPath;

                return Application.StartupPath;
            }
        }

        private static bool isInWeb
        {
            get
            {
                return HttpContext.Current != null;
            }
        }
    }
}

using System;

namespace PdfReportSamples.IList
{
    public class User
    {
        public int Id { set; get; }
        public string Name { set; get; }
        public string LastName { set; get; }
        public long Balance { set; get; }
        public DateTime RegisterDate { set; get; }
    }
}

using System;
using System.Collections.Generic;
using PdfRpt.Core.Contracts;
using PdfRpt.FluentInterface;

namespace PdfReportSamples.IList
{
    public class IListPdfReport
    {
        public IPdfReportData CreatePdfReport()
        {
            return new PdfReport().DocumentPreferences(doc =>
            {
                doc.RunDirection(PdfRunDirection.RightToLeft);
                doc.Orientation(PageOrientation.Portrait);
                doc.PageSize(PdfPageSize.A4);
                doc.DocumentMetadata(new DocumentMetadata { Author = "Vahid", Application = "PdfRpt", Keywords = "Test", Subject = "Test Rpt", Title = "Test" });
            })
            .DefaultFonts(fonts =>
            {
                fonts.Path(Environment.GetEnvironmentVariable("SystemRoot") + "\\fonts\\tahoma.ttf",
                                  Environment.GetEnvironmentVariable("SystemRoot") + "\\fonts\\verdana.ttf");
            })
            .PagesFooter(footer =>
            {
                footer.DefaultFooter(DateTime.Now.ToString("MM/dd/yyyy"));
            })
            .PagesHeader(header =>
            {
                header.DefaultHeader(defaultHeader =>
                {
                    defaultHeader.ImagePath(AppPath.ApplicationPath + "\\Images\\01.png");
                    defaultHeader.Message("گزارش جدید ما");
                });
            })
            .MainTableTemplate(template =>
            {
                template.BasicTemplate(BasicTemplate.ClassicTemplate);
            })
            .MainTablePreferences(table =>
            {
                table.ColumnsWidthsType(TableColumnWidthType.Relative);
                table.NumberOfDataRowsPerPage(5);
            })
            .MainTableDataSource(dataSource =>
            {
                var listOfRows = new List<User>();
                for (int i = 0; i < 200; i++)
                {
                    listOfRows.Add(new User { Id = i, LastName = "نام خانوادگی " + i, Name = "نام " + i, Balance = i + 1000 });
                }
                dataSource.StronglyTypedList<User>(listOfRows);
            })
            .MainTableSummarySettings(summarySettings =>
            {
                summarySettings.OverallSummarySettings("جمع کل");
                summarySettings.PerviousPageSummarySettings("نقل از صفحه قبل");
                summarySettings.PageSummarySettings("جمع صفحه");
            })
            .MainTableColumns(columns =>
            {
                columns.AddColumn(column =>
                {
                    column.PropertyName("rowNo");
                    column.IsRowNumber(true);
                    column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                    column.IsVisible(true);
                    column.Order(0);
                    column.Width(1);
                    column.HeaderCell("#");
                });

                columns.AddColumn(column =>
                {
                    column.PropertyName<User>(x => x.Id);
                    column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                    column.IsVisible(true);
                    column.Order(1);
                    column.Width(2);
                    column.HeaderCell("شماره");
                });

                columns.AddColumn(column =>
                {
                    column.PropertyName<User>(x => x.Name);
                    column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                    column.IsVisible(true);
                    column.Order(2);
                    column.Width(3);
                    column.HeaderCell("نام");
                });

                columns.AddColumn(column =>
                {
                    column.PropertyName<User>(x => x.LastName);
                    column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                    column.IsVisible(true);
                    column.Order(3);
                    column.Width(3);
                    column.HeaderCell("نام خانوادگی");
                });

                columns.AddColumn(column =>
                {
                    column.PropertyName<User>(x => x.Balance);
                    column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                    column.IsVisible(true);
                    column.Order(4);
                    column.Width(2);
                    column.HeaderCell("موجودی");
                    column.ColumnItemsTemplate(template =>
                    {
                        template.TextBlock();
                        template.DisplayFormatFormula(obj => obj == null ? string.Empty : string.Format("{0:n0}", obj));
                    });
                    column.AggregateFunction(aggregateFunction =>
                    {
                        aggregateFunction.NumericAggregateFunction(AggregateFunction.Sum);
                        aggregateFunction.DisplayFormatFormula(obj => obj == null ? string.Empty : string.Format("{0:n0}", obj));
                    });
                });

            })
            .MainTableEvents(events =>
            {
                events.DataSourceIsEmpty(message: "رکوردی یافت نشد.");
            })
            .Export(export =>
            {
                export.ToExcel();
                export.ToCsv();
                export.ToXml();
            })
            .Generate(data => data.AsPdfFile(AppPath.ApplicationPath + "\\Pdf\\RptIListSample.pdf"));
        }
    }
}

var rpt = new IListPdfReport().CreatePdfReport();
// rpt.FileName

public class StrongCoupledConcreteA
    {
        public string GenerateString(string s) { return s + " from" + this.GetType().ToString(); }
    }

    public class StrongCoupledConcreteB
    {
        public void GenerateString(ref string s) { s += " from" + this.GetType().ToString(); }
    }

    public class Printer
    {
        bool condition;
        public Printer(bool cond)
        {
            condition = cond;
        }

        public void SetCondition(bool value) { condition = value; }

        public void Print()
        {
            string result;
            string input = " this message is";
            if (condition)
            {
                var stringGenerator = new StrongCoupledConcreteA();
                result = stringGenerator.GenerateString(input);
            }
            else
            {
                var stringGenerator = new StrongCoupledConcreteB();
                result = input;
                stringGenerator.GenerateString(ref result);
            }
            Console.WriteLine(result);
        }

    }
    public class Context
    {
        Printer printer;
        public void DoWork()
        {
            printer = new Printer(true);
            printer.Print();

            printer.SetCondition(false);
            printer.Print();
        }

    }

public interface IStringGenerator
        {
            string GenerateString(string s);
        }
        public class LooslyCoupledConcreteA : IStringGenerator
        {
            public string GenerateString(string s)
            {
                return s + " from " + this.GetType().ToString();
            }
        }
        public class LooslyCoupledConcreteB : IStringGenerator
        {
            public string GenerateString(string s)
            {
                return s + " from " + this.GetType().ToString();
            }
        }

           public class Printer
           {
               bool condition;
               public Printer(bool cond)
               {
                   condition = cond;
               }

               public void SetCondition(bool value) { condition = value; }

               public void Print()
               {
                   string result;
                   string input = " this message is";
                   IStringGenerator generator;
                   if (condition)
                   {
                       generator = new LooslyCoupledConcreteA();
                   }
                   else
                   {
                       generator = new LooslyCoupledConcreteB();
                   }
                   
                   result = generator.GenerateString(input);
                   Console.WriteLine(result);

               }

           }

// single responsibility principle - bad example

    interface IEmail
    {
        void SetSender(string sender);
        void SetReceiver(string receiver);
        void SetContent(string content);
    }

    class Email : IEmail
    {
        public void SetSender(string sender)
        {
            throw new NotImplementedException();
        }
        public void SetReceiver(string receiver)
        {
            throw new NotImplementedException();
        }

        public void SetContent(string content)
        {
            throw new NotImplementedException();
        }
    }

// single responsibility principle - good example
    public interface IMessage
    {
        void SetSender(string sender);
        void SetReceiver(string receiver);
        void SetContent(IContent content);
    }

    public interface IContent
    {
        string GetAsString(); // used for serialization
    }

    public class Email : IMessage
    {        
        public void SetSender(string sender)
        {
            throw new NotImplementedException();
        }

        public void SetReceiver(string receiver)
        {
            throw new NotImplementedException();
        }

        public void SetContent(IContent content)
        {
            throw new NotImplementedException();
        }
    }

public class AreaCalculator
        {
            public double Area(object[] shapes)
            {
                double area = 0;

                foreach (var shape in shapes)
                {

                    if (shape is Square)
                    {
                        Square square = (Square)shape;
                        area += Math.Sqrt(square.Height);
                    }

                    if (shape is Triangle)
                    {
                        Triangle triangle = (Triangle)shape;
                        double TotalHalf = (triangle.FirstSide + triangle.SecondSide + triangle.ThirdSide) / 2;
                        area += Math.Sqrt(TotalHalf * (TotalHalf - triangle.FirstSide) *
                        (TotalHalf - triangle.SecondSide) * (TotalHalf - triangle.ThirdSide));
                    }

                    if (shape is Circle)
                    {
                        Circle circle = (Circle)shape;
                        area += circle.Radius * circle.Radius * Math.PI;
                    }

                }
                return area;
            }
        }
        public class Square
        {
            public double Height { get; set; }
        }
        public class Circle
        {
            public double Radius { get; set; }
        }
        public class Triangle
        {
            public double FirstSide { get; set; }
            public double SecondSide { get; set; }
            public double ThirdSide { get; set; }
        }

public class AreaCalculator
{
    public double Area(Shape[] shapes)
    {
        double area = 0;

        foreach (var shape in shapes)
        {
            area += shape.Area();
        }

        return area;
    }
}
public abstract class Shape
{
    public abstract double Area();
}
public class Square : Shape
{
    public double Height { get { return _height; } }
    private double _height;

    public Square(double Height)
    {
        _height = Height;
    }

    public override double Area()
    {
        return Math.Sqrt(_height);
    }
}
public class Circle : Shape
{
    public double Radius { get { return _radius; } }

    private double _radius;

    public Circle(double Radius)
    {
        _radius = Radius;
    }

    public override double Area()
    {
        return _radius * _radius * Math.PI;
    }
}
public class Triangle : Shape
{
    public double FirstSide { get { return _firstSide; } }
    public double SecondSide { get { return _secondSide; } }
    public double ThirdSide { get { return _thirdSide; } }

    private double _firstSide;
    private double _secondSide;
    private double _thirdSide;

    public Triangle(double FirstSide, double SecondSide, double ThirdSide)
    {
        _firstSide = FirstSide;
        _secondSide = SecondSide;
        _thirdSide = ThirdSide;
    }

    public override double Area()
    {
        double TotalHalf = (_firstSide + _secondSide + _thirdSide) / 2;
        return Math.Sqrt(TotalHalf * (TotalHalf - _firstSide) * (TotalHalf - _secondSide) * (TotalHalf - _thirdSide));
    }
}

var sequence = new[] { 12, 3, -4, 7 }.ToObservable();
var runningSum = sequence.Scan((accumulator, value) =>
{
    Console.WriteLine("accumulator {0}", accumulator);
    Console.WriteLine("value {0}", value);
    return accumulator + value;
});
runningSum.Subscribe(result => Console.WriteLine("result {0}\n", result));

result 12

accumulator 12
value 3
result 15

accumulator 15
value -4
result 11

accumulator 11
value 7
result 18

 var runningSum = sequence.Scan(seed: 10, accumulator: (accumulator, value) =>

var sequence = Enumerable.Range(1, 200)
                 .ToObservable()
                 .Buffer(count: 10);

sequence.Subscribe(onNext: numbers =>
{
   Console.WriteLine(numbers.Sum());
});

 var sequence = Enumerable.Range(1, 200)
                   .ToObservable()
                   .Buffer(timeSpan: TimeSpan.FromSeconds(2));

 var sequence = Enumerable.Range(1, 200)
                           .ToObservable()
                           .Window(timeSpan: TimeSpan.FromSeconds(2));

sequence.Subscribe(onNext: numbers =>
{
       numbers.Subscribe(onNext: number => Console.WriteLine(number));
});

 var sequence = Enumerable.Range(1, 200)
                          .ToObservable()
                          .Window(10);

sequence.Subscribe(onNext: numbers =>
{
     numbers.Sum().Subscribe(onNext: number => Console.WriteLine(number));
});