Prep for presentation

Seven.cs

// C# 6 return complex types
public class result
{
  public int Sum {get;set;}
  public int Count {get;set;}
}
public result Total(int[] values)
{
  return new result
  {
    Sum = values.Sum(),
    Count = values.Count(),
  };
}

var list = new[] {1, 2, 3, 4, 5};
var total = Total(list);
result total = Total(list);
Console.WriteLine($"{Sum {total.Sum} Count {total.Count}");

// C# 7 return tuple types
public (int sum, int count) Total(int[] values) 
{
  var s = values.Sum();
  var c = values.Count();
  return (s, c);
}

var list = new[] {1, 2, 3, 4, 5};
var total = Total(list);
(var sum, var count) total = Total(list);
(int sum, int count) total = Total(list);
Console.WriteLine($"{Sum {total.Sum} Count {total.Count}");

// C# 6 finding patterns
int? x = -3;
if (x.HasValue)
{
  var value = x.Value;
  x = Math.Abs(x);
  Console.WriteLine($"Value = {value}");
}
else
{
  Console.WriteLine($"Value is null.");
}

// C# 7 pattern matching
int? x = 3;
if (x is int v)
{
  v = Math.Abs(v);
  Console.WriteLine($"Value = {v}}");
}
else
{
  Console.WriteLine($"Value is null.");
}

// C# 6 finding patterns
var p = new Point(5, 10);
if (p.X == 5)
{
  var y = p.Y;
  y = Math.Abs(y);
  Console.Write($"Y = {y}");
}

// C# 7 positional & matching expressions
var p = new Point(5, 10);
if (p is Point { x is 5, y is var y })
{
  y = Math.Abs(y);
  Console.Write($"Y = {y}");
}

// C# 6 complex if statements
if (o is int)
{
  var i = Math.Abs(o);
  Console.WriteLine($"{i} is int")
}
else if (o is Point)
{
  var x = Math.Abs(o.X);
  var y = Math.Abs(o.Y);
  Console.WriteLine($"Point {x} {y}");
}
else if (o is string)
{
  if (o.Length > 2)
  {
    var s = o.ToLower();
    Console.WriteLine($"{s} is {s.Length}");
  }
}

// C# 7 pattern-matching switch
switch (o)
{
  case int i:
    i = Math.Abs(i);
    Console.WriteLine($"{i} is int");
    break;
  case Point(int x, int y):
    x = Math.Abs(x);
    y = Math.Abs(y);
    Console.WriteLine($"Point {x} {y}");
    Break;
  case string s when (s.Length > 0):
    s = s.ToLower();
    Console.WriteLine($"{s} is string");
}

// C# 6 comparable types
public class Person: IEquatable<Person>
{
  public int Id { get; set; }
  public string First { get; set; }
  public string Last { get; set; }
  
  public bool Equals<T>(T person)
  {
    if (person?.First != First)
    {
      return false;
    }
    else if (person?.Last != Last)
    {
      return false;
    }
    return true;
  }
}

// C# 7 (Comparable) Records
public class Person(string First, string Last);

// C# 6 Peer functions
public void Encrypter(ref User user)
{
  user.First = Encrypt(ref user.First);
  user.Middle = Encrypt(ref user.Middle);
  user.Last = Encrypt(ref user.Last);
}
public string Encrypt(ref string value) 
{ 
  // TODO 
}

// C# 7 Local  functions
public void Encrypter(ref User user)
{
  string Encrypt(ref string value) 
  {
    // TODO
  }
  user.First = Encrypt(ref user.First);
  user.Middle = Encrypt(ref user.Middle);
  user.Last = Encrypt(ref user.Last);
}

// C# 6 memory (problem)
public T Choose<T>(ref T left, ref T right)
{
  return Condition() ? left : right;
}
// new memory pointer
var path = Choose(path1, path2);

// C# 7 return ref
public ref T Choose<T>(ref T left, ref T right)
{
  return Condition() ? ref left : ref right;
}
// same memory pointer
var path = Choose(path1, path2);

// C# 6 partial methods
public partial class User // generated class
{
  public partial void Save();
}
public partial class User
{
  public partial void Save()
  {
    // TODO:  
  }
  public async Task SaveAsync()
  {
    // TODO
  }
}

// C# 7 supersede modifier
public partial class User // generated class
{
  public void Save()
  {
    // TODO
  }
}
public partial class User
{
  public supersede void Save()
  {
    // TODO:  
  }
  public supersede async Task SaveAsync()
  {
    // TODO
  }
}

// C# call-received default arguments
public class User
{
  public string First { get; set; }
  public string Last { get; set; }
  public void GetName
    (string first = null, string last = null)
  {
    if (first == null)
    {
      first = First;
    }
    if (last = null)
    {
      last = Last;
    }
    return $"{first} {last}";
    }
  }
}

// C# call-received default arguments
public class User
{
  public string First { get; set; }
  public string Last { get; set; }
  public void GetName
    (string first = this.First, string last = this.Last)
  {
    return $"{first} {last}";
  }
}

// C# 6 Clone
public class User : ICloneable
{
  public int Id { get; set; }
  public string First { get; set; }
  public string Last { get; set; }
  public object Clone()
  {
    var user = new User
    {
      First = this.First,
      Last = this.Last,
    };
  }
}
var user1 = new User
{
  Id = Guid.NewGuid(),
  First = "Jerry",
  Last = "Nixon",
}
var user2 = user1.Clone() as User;
user2.Id = Guid.NewGuid();

// C# 7 compiler-provided With method
public class User // immutable
{
  public int Id { get; set; }
  public string First { get; set; }
  public string Last { get; set; }
}
var user1 = new User
{
  Id = Guid.NewGuid(),
  First = "Jerry",
  Last = "Nixon",
}
var user2 = user1.With(Id = Guid.NewGuid());
var user2 = user with { Id = Guid.NewGuid() };

// C# 6 output results
var url = "http://bing.com";
Uri uri = null;
if (Uri.TryCreate(url, out Uri uri))
{
  // TODO: use uri
}
else
{
  throw new Exception($"Failed to cast {url}");
}

// C# 7 output var
var url = "http://bing.com";
if (Uri.TryCreate(url, out var uri))
{
  // TODO: use uri
}
else
{
  throw new Exception($"Failed to cast {url}");
}