Exploring C# 7.0: Out Variables

Using the out keyword within C# is nothing new. If you declare a variable within a method called with out, you are instructing the compile that you are expecting the method to set the values of those at runtime.

class Program
{
  static void Main(string[] args)
  {
    string firstName;
    string lastName;

    CreateName(out firstName, out lastName);
    Console.WriteLine($"Hello {firstName} {lastName}");
  }

  private static void CreateName(out string firstName, out string lastName)
  {
    firstName = "Kevin";
    lastName = "Griffin";
  }
}

Commonly the problem is that you have to declare the variable before the method call using out. In C# 7.0, there is the concept of out variables, which will save you a couple keystrokes by allowing you to declare the variable inline.

The above example can be quickly refactored:

class Program
{
  static void Main(string[] args)
  {
    // notice I'm declaring the type INSIDE THE CALL!
    CreateName(out string firstName, out string lastName);
    Console.WriteLine($"Hello {firstName} {lastName}");
  }

  private static void CreateName(out string firstName, out string lastName)
  {
    firstName = "Kevin";
    lastName = "Griffin";
  }
}