What are Ref local variables and Ref return values ​​in C# 7.0?

Reference return values ​​allow methods to return a reference to a variable instead of than a value.

The caller can choose to treat the returned variable as value or reference.

The caller can create a new variable, which itself is a reference to the return value, called ref local.

In the example below, even if we modify the color it has no effect Raw array colors

Example

class Program{
   public static void Main(){
      var colors = new[] { "blue", "green", "yellow", "orange", "pink" };
      string color = colors[3];
      color = "Magenta";
      System.Console.WriteLine(String.Join(" ", colors));
      Console.ReadLine();
   }
}

Output

blue green yellow orange pink

To achieve this we can use ref locals

Example

public static void Main(){
   var colors = new[] { "blue", "green", "yellow", "orange", "pink" };
   ref string color = ref colors[3];
   color = "Magenta";
   System.Console.WriteLine(String.Join(" ", colors));
   Console.ReadLine();
}

Output

blue green yellow Magenta pink

Ref returns -

In the example below, even if we modify the color, it will not have any impact Original array color

Example

class Program{
   public static void Main(){
      var colors = new[] { "blue", "green", "yellow", "orange", "pink" };
      string color = GetColor(colors, 3);
      color = "Magenta";
      System.Console.WriteLine(String.Join(" ", colors));
      Console.ReadLine();
   }
   public static string GetColor(string[] col, int index){
      return col[index];
   }
}

Output

blue green yellow orange pink

Example

class Program{
   public static void Main(){
      var colors = new[] { "blue", "green", "yellow", "orange", "pink" };
      ref string color = ref GetColor(colors, 3);
      color = "Magenta";
      System.Console.WriteLine(String.Join(" ", colors));
      Console.ReadLine();
   }
   public static ref string GetColor(string[] col, int index){
      return ref col[index];
   }
}

Output

blue green yellow Magenta pink

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