ReSharper 2017.2 Help

Extract Interface refactoring

ReSharper | Refactor | Extract | Extract Interface…
ReSharper_ExtractInterface

This refactoring helps create a new interface based on a selected type. ReSharper suggests to choose members to 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 also be 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.
  2. Do one of the following:
    • Press Ctrl+Shift+R and then choose Extract Interface
    • Right-click and choose Refactor | Extract Interface in 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 and technologies:

Language: C#
Language: VB.NET
Language: C++
Language: HTML
Language: ASP.NET
Language: Razor
Language: JavaScript
Language: TypeScript
Language: CSS
Language: XML
Language: XAML
Language: Resx
Language: Build Scripts
Language: Protobuf
Language: JSON
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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.

Last modified: 12 October 2017

See Also