C# 6.0 (C# vNext) 新功能之：Expression Bodied Functions and Properties

Expression Bodied Function 可以用在：

• methods
• user-defined operators
• type conversions
• read-only properties 
• indexers

看以下的例子：

public class RgbColor(int r, int g, int b)
{
  public int Red { get; } = r;
  public int Green { get; } = g;
  public int Blue { get; } = b;
 
  public string ToHex() =>
    string.Format("#{0:X2}{1:X2}{2:X2}", Red, Green, Blue);
 
  public static RgbColor operator - (RgbColor color) =>
    new RgbColor(
      color.Red ^ 0xFF,
      color.Green ^ 0xFF,
      color.Blue ^ 0xFF
    );
}

用於「方法」的例子：

public string ToHex() => string.Format("#{0:X2}{1:X2}{2:X2}", Red, Green, Blue);
public override string ToString() => this.Name;

用於「user-defined operators」的例子：

  public static RgbColor operator - (RgbColor color) =>
    new RgbColor(
      color.Red ^ 0xFF,
      color.Green ^ 0xFF,
      color.Blue ^ 0xFF
    );

public static Complex operator +(Complex a, Complex b) => a.Add(b);

用於「read-only property」的例子：
特別注意，這是 Read Only Property 而不是 Field 

public string ID => Guid.NewGuid().ToString();

又一個例子：

public class Point(int x, int y) {
    public int X => x;
    public int Y => y;
    public double Dist => Math.Sqrt(x * x + y * y);
    public Point Move(int dx, int dy) => new Point(x + dx, y + dy);
}

用於「type conversions」的例子：實現 string 和 Name 之間的隱性轉換

public static implicit operator string(Name n) => n.First + " " + n.Last;

用於「indexers」的例子：

public Customer this[Id id] => store.LookupCustomer(id);