Extract Interface

• Aug 03, 2020
• 3 minutes to read

Extracts an interface of public members from a class.

Purpose

This refactoring is a great first step for changing your code, because it uses interfaces instead of specific classes. It allows you to create a new interface based on the class you used previously, and makes that class implement that interface.

Availability

Available when the caret is on a class declaration statement. The caret should be on the class name and the class should have at least one public member.

NOTE

• The resulting interface is declared right above the source class.
• Rename is automatically invoked for the newly declared interface.

Usage

1. Place the caret on a class declaration.

   NOTE

   The blinking cursor shows the caret's position at which the Refactoring is available.

   C#

   class │ProductInfo
   {
       private int _unitPrice;
       private int _count;
       private int _UnitPrice;
       public int UnitPrice
       {
           get { return _UnitPrice; }
           set { _UnitPrice = value; }
       }
       public int Count
       {
           get { return _count; }
           set { _count = value; }
       }
   }
   

   VB.NET

   Public Class │ProductInfo
       Private _unitPrice As Integer
       Private _count As Integer
       Public Property unitPrice() As Integer
           Get
               Return _unitPrice
           End Get
           Set(ByVal value As Integer)
               _unitPrice = value
           End Set
       End Property
       Public Property count() As Integer
           Get
               Return _count
           End Get
           Set(ByVal value As Integer)
               _count = value
           End Set
       End Property
   End Class
   

2. Use the Ctrl + . or Ctrl + ~ shortcut to invoke the Code Actions Menu.
3. Select Extract Interface from the menu.

After execution, the Refactoring creates a new interface based on the class you used previously, and makes that class implement that interface.

C#

internal interface MyInterface
{
    int UnitPrice { get; set; }
    int Count { get; set; }
}
class ProductInfo : IProductInfo
{
    private int _unitPrice;
    private int _count;
    private int _UnitPrice;
    public int UnitPrice
    {
        get { return _UnitPrice; }
        set { _UnitPrice = value; }
    }
    public int Count
    {
        get { return _count; }
        set { _count = value; }
    }
}

VB.NET

Public Interface MyInterface
    Property unitPrice() As Integer
    Property count() As Integer
End Interface
Public Class ProductInfo
    Implements MyInterface
    Private _unitPrice As Integer
    Private _count As Integer
    Public Property unitPrice() As Integer Implements MyInterface.unitPrice
        Get
            Return _unitPrice
        End Get
        Set(ByVal value As Integer)
            _unitPrice = value
        End Set
    End Property
    Public Property count() As Integer Implements MyInterface.count
        Get
            Return _count
        End Get
        Set(ByVal value As Integer)
            _count = value
        End Set
    End Property
End Class