[Fork] C# 8.0 New Feature | C# Online Compiler

[Fork] C# 8.0 New Feature by Ideacore Developer

using System;
using System.Linq;
using System.IO;

public class Program
{
	public static void Main()
	{
		Console.WriteLine("C# 8.0 New Feature Swtich Expressions ..."); 
		
		//ex_switch_expressions.print();//1
		//ex_indices_and_ranges.print();//2
		//ex_default_interface_members.print();//3
		//ex_static_local_functions.print();//4
		//ex_using_declarations.print();//5
		//ex_nullable_reference_types.print();//6
		//ex_readonly_struct_members.print();//7
		//ex_null_coalescing_assignment.print();//8
		//ex_async_streams.print();//9
		ex_property_tuple_and_positional_patterns.print();//10
	}
}

//switch expressions
public class ex_switch_expressions
{
	public static void print()    
	{    
		Console.WriteLine("[1] Swtich Expressions");    

		//example1    
		var (a, b, option) = (10, 5, "+");    

		var example1 = option switch    
		{    
				"+" => a + b,    
				"-" => a - b,    
				_ => a * b    
		};    
		Console.WriteLine("Example-1: " + example1);    

		//example2    
		var value = 25;    

		int example2 = value switch    
		{    
				_ when value > 10 => 0,    
				_ when value <= 10 => 1    
		};    
		Console.WriteLine("Example-2: " + example2);    
		
		//example3
		Console.WriteLine("Example-3... ");  
		Calculation c1 = new Calculation(50, 10, "*");
		c1.print();
		
  		Calculation c2 = new Calculation(50, 10, "+");
		c2.print();
	}  
}


public class Calculation    
{    
	public Calculation(int a, int b, string operation)    
	{    
		this.FirstNumber = a;    
		this.SecondNumber = b;    
		this.Operation = operation;  
		
		this.ResultNumber = this.Operation switch    
		{    
				"+" => this.FirstNumber + this.SecondNumber,    
				"-" => this.FirstNumber - this.SecondNumber,    
				"/" => this.FirstNumber / this.SecondNumber,    
				"*" => this.FirstNumber * this.SecondNumber,    
				_ => -1   
		}; 
	}    

	public int FirstNumber { get; set; }    

	public int SecondNumber { get; set; }    

	public string Operation { get; set; }    

	public int ResultNumber { get; set; }    
	
	public void print()
	{
		Console.WriteLine($"{this.FirstNumber} {this.Operation} {this.SecondNumber} = {this.ResultNumber}");  
	}

}

//Indices and Ranges
public class ex_indices_and_ranges
{
	public static void print()
	{
		Console.WriteLine("[2] Indices and Ranges");  
		
		//example1
		Index d1 = 2; // number 2 from beginning  
		Index d2 = ^ 3; // number 3 from end  
		string[] week = {  
			"Monday",  
			"Tuesday",  
			"Wednesday",  
			"Thursday",  
			"Friday",  
			"Saturday",  
			"Sunday"  
		};  
		Console.WriteLine($"Example-1: {week[d1]}, {week[d2]}"); //o/p => Wednesday , Friday	
		
		//example2
		//Old Style  
		var lastDayOldStyle = week[week.Length -1]; // Sanday  
		//New Style  
		var lastDayNewStyle = week[^1]; // Sanday 
		
		Console.WriteLine($"Example-2: {lastDayOldStyle}, {lastDayNewStyle}"); //o/p =>  Sanday , Sanday	
		
		//example3
		Console.WriteLine($"Example-3... ");
		//Old Style  
		Console.WriteLine($"Way-1 => ");
		var days = week.ToList().GetRange(2, 3); // Wednesday,Thursday,Friday  
		foreach(var item in days)
		{
			Console.WriteLine($"{item}");
		}
		//or  
		Console.WriteLine($"Way-2 => ");
		var days1 = week.Skip(2).Take(3); // Wednesday,Thursday,Friday  
		foreach(var item in days1)
		{
			Console.WriteLine($"{item}");
		}
		//New Style  
		Console.WriteLine($"Way-3 => ");
		var days2 = week[1.. ^ 2]; // Wednesday,Thursday,Friday  
		foreach(var item in days2)
		{
			Console.WriteLine($"{item}");
		}
		// [1..^2] mean   
		//  1 : skip elements from the begining until the index 1  
		// ^2 : skip 2 element from the end
	}
}

//default interface members
public class ex_default_interface_members
{
	public static void print()
	{
		Console.WriteLine("[3] default interface members");  
		
		Printer p = new Printer();
		p.Print(".Net", "Fiddle");
		
		IWriteLine obj = new WriteLine();
		obj.WriteLine();
		//example1
		
	}
}

public interface IPrintable {  
	void Print(string header, string text);  
	// New overloadvoid Print(Document doc) => Print(doc.Header, doc.Text);   
}  

public class Printer: IPrintable {  
	public void Print(string header, string text) {  
		Console.WriteLine($"header = {header} and text = {text}");
	}  
	// Print(Document) gets default implementation  
}  

public interface IWriteLine  
{  
	 public void WriteLine()  
	 {  
	 	Console.WriteLine("Wow C# 8!");  
	 }  
} 

public class WriteLine : IWriteLine  
{  
 
} 


//static local functions
public class ex_static_local_functions
{
	public static void print()
	{
		Console.WriteLine("[4] static local functions");  
		
		//example1
		Employee emp1 = new Employee();
		emp1.MethodWithLocalFunction(125);
		emp1.MethodWithStaticLocalFunction(515);
		
	}
}

public class Employee
{
	public void MethodWithLocalFunction(int input)
	{
		Console.WriteLine($"Inside MethodWithLocalFunction, input: {input}.");
		LocalFunction();

		void LocalFunction()
		{
			Console.WriteLine($"Inside LocalFunction, input: {input}.");
		}
	}
	
	public void MethodWithStaticLocalFunction(int input)
	{
		Console.WriteLine($"Inside MethodWithStaticLocalFunction, input: {input}.");
		StaticLocalFunction(input);

		static void StaticLocalFunction(int input)
		{
			Console.WriteLine($"Inside StatucLocalFunction, input: {input}.");
		}
	}

}

//using declarations
public class ex_using_declarations
{
	public static void print()
	{
		Console.WriteLine("[5] using declarations");  
		
		//example1
		using(var fileStream = new FileStream("abcd.txt",FileMode.Open))  
		{  
			//do somthing here  
		}// fileStream dispose here  
		
		var fileName = "abcd.txt";  
		if(fileName != null)  
		{  
			using var fileStream = new FileStream(fileName, FileMode.Open);  

			//do somthing here  
		}// fileStream dispose here
	}
}

//Nullable reference types
public class ex_nullable_reference_types
{
	public static void print()
	{
		Console.WriteLine("[6] Nullable reference types");  
		
		//example1
		string? nullableString = null;  
		Console.WriteLine(nullableString.Length); // WARNING: may be null! Take care! 
	}
}

//readonly struct members
public class ex_readonly_struct_members
{
	public static void print()
	{
		Console.WriteLine("[7] readonly struct members");  
		
		//example1
		Point obj = new Point();
		obj.X = 2;
		obj.Y = 3;
		Console.WriteLine(obj.Distance);
	}
}

public struct Point
{
    public double X { get; set; }
    public double Y { get; set; }
	public readonly double Distance => Math.Sqrt(X * X + Y * Y);
}

//Null-coalescing assignment
public class ex_null_coalescing_assignment
{
	public static void print()
	{
		Console.WriteLine("[8] Null-coalescing assignment");  
		
		//example1
		int? i = 1;
		int j = 2;
		
		i ??= j;
		
		Console.WriteLine($"{i}");  
		
		//example1
		int? variable = null;
		int expression = 5;
		
		if (variable == null)  
		{  
		  variable = expression; // C# 1..7  
		}  
		variable ??= expression; // C# 8 
		Console.WriteLine($"{variable}"); 

	}
}

//Async Streams
public class ex_async_streams
{
	public static async void print()
	{
		Console.WriteLine("[9] Async Streams");  
		
		//example1
		await foreach (var number in GenerateSequence())
		{
			Console.WriteLine(number);
		}
	}
	
	public static async System.Collections.Generic.IAsyncEnumerable<int> GenerateSequence()
	{
		for (int i = 0; i < 20; i++)
		{
			await System.Threading.Tasks.Task.Delay(100);
			yield return i;
		}
	}
	
}

//Property, Tuple, and positional patterns
public class ex_property_tuple_and_positional_patterns
{
	public static void print()
	{
		Console.WriteLine("[10] Property, Tuple, and positional patterns");  
		
		//example1: Property
		Address location = new Address();
		location.State = "MN";
		decimal salePrice = 10;
		
		Console.WriteLine(ComputeSalesTax(location, salePrice));
		
		//OR
		/*
		if (sword is Sword { Damage: 10, Durability: var durability })
		{
			// code executes if Damage = 10
			// durability has value of sword.Durability
		}
		*/
		
		//example2: Tuple
		Console.WriteLine(RockPaperScissors("rock", "paper"));
		
		//example3: positional
		Point2 obj = new Point2(1, 5);
		Console.WriteLine(GetQuadrant(obj));
	}
	
	public static decimal ComputeSalesTax(Address location, decimal salePrice) => location switch
    {
        { State: "WA" } => salePrice * 0.06M,
        { State: "MN" } => salePrice * 0.75M,
        { State: "MI" } => salePrice * 0.05M,
        // other cases removed for brevity...
        _ => 0M
    };
	
	public static string RockPaperScissors(string first, string second) => (first, second) switch
    {
        ("rock", "paper") => "rock is covered by paper. Paper wins.",
        ("rock", "scissors") => "rock breaks scissors. Rock wins.",
        ("paper", "rock") => "paper covers rock. Paper wins.",
        ("paper", "scissors") => "paper is cut by scissors. Scissors wins.",
        ("scissors", "rock") => "scissors is broken by rock. Rock wins.",
        ("scissors", "paper") => "scissors cuts paper. Scissors wins.",
        (_, _) => "tie"
    };
	
	static Quadrant GetQuadrant(Point2 point) => point switch
	{
		(0, 0) => Quadrant.Origin,
		var (x, y) when x > 0 && y > 0 => Quadrant.One,
		var (x, y) when x < 0 && y > 0 => Quadrant.Two,
		var (x, y) when x < 0 && y < 0 => Quadrant.Three,
		var (x, y) when x > 0 && y < 0 => Quadrant.Four,
		var (_, _) => Quadrant.OnBorder,
		_ => Quadrant.Unknown
	};

}

public class Address
{
	public string State;
}

public enum Quadrant
{
    Unknown,
    Origin,
    One,
    Two,
    Three,
    Four,
    OnBorder
}

public class Point2
{
    public int X { get; }
    public int Y { get; }

    public Point2(int x, int y) => (X, Y) = (x, y);

    public void Deconstruct(out int x, out int y) =>
        (x, y) = (X, Y);
}

/*

https://dotnetfiddle.net/

C# 8 ...
https://en.wikipedia.org/wiki/C_Sharp_(programming_language)

C# 8 in VS 2019 ...
https://www.c-sharpcorner.com/article/c-sharp-8-0-new-feature-swtich-expression/
https://www.c-sharpcorner.com/article/whats-new-in-c-sharp-8/
https://www.c-sharpcorner.com/article/c-sharp-8-0-new-feature-using-declaration-and-static-local-function/
https://www.c-sharpcorner.com/article/c-sharp-8-features/
https://codeblog.jonskeet.uk/category/c-8/
https://www.dotnetcurry.com/csharp/1489/csharp-8-visual-studio-2019
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8#null-coalescing-assignment

-----

C# 8.0

===>1 => switch expressions
===>2 => Indices and Ranges
===>3 => default interface members
===>4 => static local functions
===>5 => using declarations
===>6 => Nullable reference types
===>7 => readonly struct members
===>8 => Null-coalescing assignment
===>9 => Async Streams
===>10 => Property, Tuple, and positional patterns

Disposable ref struct
-----

Blg Top
1 => Email file download
2 => Authentication and Authorization using filter
3 => Upload file validation using javascript
4 => Custom excel generation
5 => Show loader while pdf/report generate/download
6 => Data validation using Dataannotation
7 => Bundelling and minification using mvc
8 => Service based app architecture using mvc
9 => One image on another image
10 => Error handling UI
11 => Model state, check validate, add error, etc.
12 => C# new features all in detail like series
*/

​x
 
using System;
using System.Linq;
using System.IO;
​
public class Program
{
    public static void Main()
    {
        Console.WriteLine("C# 8.0 New Feature Swtich Expressions ..."); 
        
        //ex_switch_expressions.print();//1
        //ex_indices_and_ranges.print();//2
        //ex_default_interface_members.print();//3
        //ex_static_local_functions.print();//4
        //ex_using_declarations.print();//5
        //ex_nullable_reference_types.print();//6
        //ex_readonly_struct_members.print();//7
        //ex_null_coalescing_assignment.print();//8
        //ex_async_streams.print();//9
        ex_property_tuple_and_positional_patterns.print();//10
    }
}
​
//switch expressions
public class ex_switch_expressions
{
    public static void print()    
    {    
        Console.WriteLine("[1] Swtich Expressions");    
​
        //example1    
        var (a, b, option) = (10, 5, "+");    
​
        var example1 = option switch    
        {    
                "+" => a + b,    
                "-" => a - b,    
                _ => a * b    
        };    
        Console.WriteLine("Example-1: " + example1);    
​
        //example2    
        var value = 25;    
​
        int example2 = value switch    
        {    
                _ when value > 10 => 0,    
                _ when value <= 10 => 1    
        };    
        Console.WriteLine("Example-2: " + example2);    
        
        //example3
        Console.WriteLine("Example-3... ");  
        Calculation c1 = new Calculation(50, 10, "*");
        c1.print();
        
        Calculation c2 = new Calculation(50, 10, "+");
        c2.print();
    }  
}
​
​
public class Calculation    
{    
    public Calculation(int a, int b, string operation)    
    {    
        this.FirstNumber = a;    
        this.SecondNumber = b;    
        this.Operation = operation;  
        
        this.ResultNumber = this.Operation switch    
        {    
                "+" => this.FirstNumber + this.SecondNumber,    
                "-" => this.FirstNumber - this.SecondNumber,    
                "/" => this.FirstNumber / this.SecondNumber,    
                "*" => this.FirstNumber * this.SecondNumber,    
                _ => -1   
        }; 
    }    
​
    public int FirstNumber { get; set; }    
​
    public int SecondNumber { get; set; }    
​
    public string Operation { get; set; }    
​
    public int ResultNumber { get; set; }    
    
    public void print()
    {
        Console.WriteLine($"{this.FirstNumber} {this.Operation} {this.SecondNumber} = {this.ResultNumber}");  
    }
​
}
​
//Indices and Ranges
public class ex_indices_and_ranges
{
    public static void print()
    {
        Console.WriteLine("[2] Indices and Ranges");  
        
        //example1
        Index d1 = 2; // number 2 from beginning  
        Index d2 = ^ 3; // number 3 from end  
        string[] week = {  
            "Monday",  
            "Tuesday",  
            "Wednesday",  
            "Thursday",  
            "Friday",  
            "Saturday",  
            "Sunday"  
        };  
        Console.WriteLine($"Example-1: {week[d1]}, {week[d2]}"); //o/p => Wednesday , Friday    
        
        //example2
        //Old Style  
        var lastDayOldStyle = week[week.Length -1]; // Sanday  
        //New Style  
        var lastDayNewStyle = week[^1]; // Sanday 
        
        Console.WriteLine($"Example-2: {lastDayOldStyle}, {lastDayNewStyle}"); //o/p =>  Sanday , Sanday    
        
        //example3
        Console.WriteLine($"Example-3... ");
        //Old Style  
        Console.WriteLine($"Way-1 => ");
        var days = week.ToList().GetRange(2, 3); // Wednesday,Thursday,Friday  
        foreach(var item in days)
        {
            Console.WriteLine($"{item}");
        }
        //or  
        Console.WriteLine($"Way-2 => ");
        var days1 = week.Skip(2).Take(3); // Wednesday,Thursday,Friday  
        foreach(var item in days1)
        {
            Console.WriteLine($"{item}");
        }
        //New Style  
        Console.WriteLine($"Way-3 => ");
        var days2 = week[1.. ^ 2]; // Wednesday,Thursday,Friday  
        foreach(var item in days2)
        {
            Console.WriteLine($"{item}");
        }
        // [1..^2] mean   
        //  1 : skip elements from the begining until the index 1  
        // ^2 : skip 2 element from the end
    }
}
​
//default interface members
public class ex_default_interface_members
{
    public static void print()
    {
        Console.WriteLine("[3] default interface members");  
        
        Printer p = new Printer();
        p.Print(".Net", "Fiddle");
        
        IWriteLine obj = new WriteLine();
        obj.WriteLine();
        //example1
        
    }
}
​
public interface IPrintable {  
    void Print(string header, string text);  
    // New overloadvoid Print(Document doc) => Print(doc.Header, doc.Text);   
}  
​
public class Printer: IPrintable {  
    public void Print(string header, string text) {  
        Console.WriteLine($"header = {header} and text = {text}");
    }  
    // Print(Document) gets default implementation  
}  
​
public interface IWriteLine  
{  
     public void WriteLine()  
     {  
        Console.WriteLine("Wow C# 8!");  
     }  
} 
​
public class WriteLine : IWriteLine  
{  
 
} 
​
​
//static local functions
public class ex_static_local_functions
{
    public static void print()
    {
        Console.WriteLine("[4] static local functions");  
        
        //example1
        Employee emp1 = new Employee();
        emp1.MethodWithLocalFunction(125);
        emp1.MethodWithStaticLocalFunction(515);
        
    }
}
​
public class Employee
{
    public void MethodWithLocalFunction(int input)
    {
        Console.WriteLine($"Inside MethodWithLocalFunction, input: {input}.");
        LocalFunction();
​
        void LocalFunction()
        {
            Console.WriteLine($"Inside LocalFunction, input: {input}.");
        }
    }
    
    public void MethodWithStaticLocalFunction(int input)
    {
        Console.WriteLine($"Inside MethodWithStaticLocalFunction, input: {input}.");
        StaticLocalFunction(input);
​
        static void StaticLocalFunction(int input)
        {
            Console.WriteLine($"Inside StatucLocalFunction, input: {input}.");
        }
    }
​
}
​
//using declarations
public class ex_using_declarations
{
    public static void print()
    {
        Console.WriteLine("[5] using declarations");  
        
        //example1
        using(var fileStream = new FileStream("abcd.txt",FileMode.Open))  
        {  
            //do somthing here  
        }// fileStream dispose here  
        
        var fileName = "abcd.txt";  
        if(fileName != null)  
        {  
            using var fileStream = new FileStream(fileName, FileMode.Open);  
​
            //do somthing here  
        }// fileStream dispose here
    }
}
​
//Nullable reference types
public class ex_nullable_reference_types
{
    public static void print()
    {
        Console.WriteLine("[6] Nullable reference types");  
        
        //example1
        string? nullableString = null;  
        Console.WriteLine(nullableString.Length); // WARNING: may be null! Take care! 
    }
}
​
//readonly struct members
public class ex_readonly_struct_members
{
    public static void print()
    {
        Console.WriteLine("[7] readonly struct members");  
        
        //example1
        Point obj = new Point();
        obj.X = 2;
        obj.Y = 3;
        Console.WriteLine(obj.Distance);
    }
}
​
public struct Point
{
    public double X { get; set; }
    public double Y { get; set; }
    public readonly double Distance => Math.Sqrt(X * X + Y * Y);
}
​
//Null-coalescing assignment
public class ex_null_coalescing_assignment
{
    public static void print()
    {
        Console.WriteLine("[8] Null-coalescing assignment");  
        
        //example1
        int? i = 1;
        int j = 2;
        
        i ??= j;
        
        Console.WriteLine($"{i}");  
        
        //example1
        int? variable = null;
        int expression = 5;
        
        if (variable == null)  
        {  
          variable = expression; // C# 1..7  
        }  
        variable ??= expression; // C# 8 
        Console.WriteLine($"{variable}"); 
​
    }
}
​
//Async Streams
public class ex_async_streams
{
    public static async void print()
    {
        Console.WriteLine("[9] Async Streams");  
        
        //example1
        await foreach (var number in GenerateSequence())
        {
            Console.WriteLine(number);
        }
    }
    
    public static async System.Collections.Generic.IAsyncEnumerable<int> GenerateSequence()
    {
        for (int i = 0; i < 20; i++)
        {
            await System.Threading.Tasks.Task.Delay(100);
            yield return i;
        }
    }
    
}
​
//Property, Tuple, and positional patterns
public class ex_property_tuple_and_positional_patterns
{
    public static void print()
    {
        Console.WriteLine("[10] Property, Tuple, and positional patterns");  
        
        //example1: Property
        Address location = new Address();
        location.State = "MN";
        decimal salePrice = 10;
        
        Console.WriteLine(ComputeSalesTax(location, salePrice));
        
        //OR
        /*
        if (sword is Sword { Damage: 10, Durability: var durability })
        {
            // code executes if Damage = 10
            // durability has value of sword.Durability
        }
        */
        
        //example2: Tuple
        Console.WriteLine(RockPaperScissors("rock", "paper"));
        
        //example3: positional
        Point2 obj = new Point2(1, 5);
        Console.WriteLine(GetQuadrant(obj));
    }
    
    public static decimal ComputeSalesTax(Address location, decimal salePrice) => location switch
    {
        { State: "WA" } => salePrice * 0.06M,
        { State: "MN" } => salePrice * 0.75M,
        { State: "MI" } => salePrice * 0.05M,
        // other cases removed for brevity...
        _ => 0M
    };
    
    public static string RockPaperScissors(string first, string second) => (first, second) switch
    {
        ("rock", "paper") => "rock is covered by paper. Paper wins.",
        ("rock", "scissors") => "rock breaks scissors. Rock wins.",
        ("paper", "rock") => "paper covers rock. Paper wins.",
        ("paper", "scissors") => "paper is cut by scissors. Scissors wins.",
        ("scissors", "rock") => "scissors is broken by rock. Rock wins.",
        ("scissors", "paper") => "scissors cuts paper. Scissors wins.",
        (_, _) => "tie"
    };
    
    static Quadrant GetQuadrant(Point2 point) => point switch
    {
        (0, 0) => Quadrant.Origin,
        var (x, y) when x > 0 && y > 0 => Quadrant.One,
        var (x, y) when x < 0 && y > 0 => Quadrant.Two,
        var (x, y) when x < 0 && y < 0 => Quadrant.Three,
        var (x, y) when x > 0 && y < 0 => Quadrant.Four,
        var (_, _) => Quadrant.OnBorder,
        _ => Quadrant.Unknown
    };
​
}
​
public class Address
{
    public string State;
}
​
public enum Quadrant
{
    Unknown,
    Origin,
    One,
    Two,
    Three,
    Four,
    OnBorder
}
​
public class Point2
{
    public int X { get; }
    public int Y { get; }
​
    public Point2(int x, int y) => (X, Y) = (x, y);
​
    public void Deconstruct(out int x, out int y) =>
        (x, y) = (X, Y);
}
​
/*
​
https://dotnetfiddle.net/
​
C# 8 ...
https://en.wikipedia.org/wiki/C_Sharp_(programming_language)
​
C# 8 in VS 2019 ...
https://www.c-sharpcorner.com/article/c-sharp-8-0-new-feature-swtich-expression/
https://www.c-sharpcorner.com/article/whats-new-in-c-sharp-8/
https://www.c-sharpcorner.com/article/c-sharp-8-0-new-feature-using-declaration-and-static-local-function/
https://www.c-sharpcorner.com/article/c-sharp-8-features/
https://codeblog.jonskeet.uk/category/c-8/
https://www.dotnetcurry.com/csharp/1489/csharp-8-visual-studio-2019
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8#null-coalescing-assignment
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C# 8.0
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===>1 => switch expressions
===>2 => Indices and Ranges
===>3 => default interface members
===>4 => static local functions
===>5 => using declarations
===>6 => Nullable reference types
===>7 => readonly struct members
===>8 => Null-coalescing assignment
===>9 => Async Streams
===>10 => Property, Tuple, and positional patterns
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Disposable ref struct
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Blg Top
1 => Email file download
2 => Authentication and Authorization using filter
3 => Upload file validation using javascript
4 => Custom excel generation
5 => Show loader while pdf/report generate/download
6 => Data validation using Dataannotation
7 => Bundelling and minification using mvc
8 => Service based app architecture using mvc
9 => One image on another image
10 => Error handling UI
11 => Model state, check validate, add error, etc.
12 => C# new features all in detail like series
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