ReSharper Help

Extract Interface

ReSharper | Refactor | Extract | Extract Interface…
ReSharper_ExtractInter

This refactoring helps create a new interface based on a selected type. ReSharper suggests you to choose which members should be transferred to the new interface. After extraction, the original type is updated to implement the new interface.
If the current type already implements any interfaces, these interfaces can be also extracted into the new interface.

In the example below, the Color property and the Draw method of the Circle class are extracted to create a new interface:

Before refactoringAfter refactoring
class Circle { public Point Center { get; private set; } public Color Color { get; private set; } public int Radius { get; private set; } public void Draw() { // draw... } }
interface IShape { Color Color { get; } void Draw(); } class Circle : IShape { public Point Center { get; private set; } public Color Color { get; private set; } public int Radius { get; private set; } public void Draw() { // draw... } }

To extract an interface from a type

  1. Select a type in one of the following ways:
    • In the editor, set the caret at the name of a type.
    • Select a type in the Solution Explorer.
    • Select a type in the File Structure window.
    • Select a type in the Class View.
    • Select a type in the Object Browser.
    • Select a type in the type dependency diagram.
    Or, alternatively, select one or several members you want to extract in the editor or in a tool window.
  2. Do one of the following:
    • Press Ctrl+Shift+R and then choose Extract Interface
    • Right-click and choose Refactor | Extract Interface on the context menu.
    • Choose ReSharper | Refactor | Extract | Extract Interface… in the main menu.
    The Extract Interface dialog will open.
  3. Specify a name for the interface and where it should be placed - in a new file or in the same file as the original type.
  4. Select members that you want to transfer to the new interface. The list of members can contain:
    • Members of the current type
    • Members of base types that the selected type currently inherits/implements
    • Interfaces that the selected type currently implements
  5. To quickly select all public members, click All Public.
  6. If you have selected members that reference other members, the latter are highlighted with red. Click Dependent to resolve the conflict, i.e. to select any members that depend on the currently selected members.
  7. To apply the refactoring, click Next.
  8. If no conflicts are found, ReSharper performs the refactoring immediately. Otherwise, it prompts you to resolve conflicts.
ReSharper. Extracting interface from a class

This feature is supported in the following languages/technologies:

C# VB.NET C++ HTML ASPX Razor JavaScript TypeScript CSS XML XAML RESX Build Scripts
feature_available feature_available feature_available

The instructions and examples given here address the use of the feature in C#. For details specific to other languages, see corresponding topics in the ReSharper by Language section.

See Also

Last modified: 3 September 2015