C# Automatic Properties

First posted at: http://blogs.microsoft.co.il/blogs/maordavid/archive/2007/09/26/c-automatic-properties.aspx

Visual Studio 2008 and .NET 3.5 introduces us new feature: Automatic Properties.

You probably write classes with properties like this:

   1:  public class Student

   2:  {

   3:      private string _firstName;

   4:   

   5:      public string FirstName

   6:      {

   7:          get { return _firstName; }

   8:          set { _firstName = value; }

   9:      }

  10:   

  11:      private string _lastName;

  12:   

  13:      public string LastName

  14:      {

  15:          get { return _lastName; }

  16:          set { _lastName = value; }

  17:      }

  18:   

  19:      private string faculty;

  20:   

  21:      public string Faculty

  22:      {

  23:          get { return faculty; }

  24:          set { faculty = value; }

  25:      }

  26:   

  27:  }

 

Usually, you aren't actually adding any logic in the getters/setters of your properties - instead you just get/set the value directly to a field.

Basically, automatic properties allow you to replace this common pattern with this one:

   1:  public class Student

   2:  {

   3:      public string FirstName

   4:      {

   5:          get; set;

   6:      }

   7:   

   8:   

   9:      public string LastName

  10:      {

  11:          get; set;

  12:      }

  13:   

  14:   

  15:      public string Faculty

  16:      {

  17:          get; set;

  18:      }

  19:  }

No fields, only properties and declarations of get/set. The compiler can automate creating the private field and the default get/set operations for you.

This is certainly much more compact and requires fewer steps. When the compiler sees this class, (according to Reflector) it translates it to:

public class Student
{
    // Fields
    [CompilerGenerated]
    private string <Faculty>k__BackingField;
    [CompilerGenerated]
    private string <FirstName>k__BackingField;
    [CompilerGenerated]
    private string <LastName>k__BackingField;

    // Methods
    public Student();

    // Properties
    public string Faculty { [CompilerGenerated] get; [CompilerGenerated] set; }
    public string FirstName { [CompilerGenerated] get; [CompilerGenerated] set; }
    public string LastName { [CompilerGenerated] get; [CompilerGenerated] set; }
}

There are a few things to look out for when using this syntax. The compiler forces you to declare properties with both a get and a set. You also don't get any kind of "safety" features, such as ensuring that you don't allow a null value to be assigned to a string property. If you want these more "advanced" features, you'll still need to define your property with the "old way".

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