Extract an Interface from a Class in JetBrains Rider

Problem and takeaway

You have a concrete C# class whose methods and properties are referenced directly by other code. When you need to swap the implementation—for example, to insert a test double or an alternative service—every consumer still depends on the concrete type, so the change ripples through the solution.

Useful takeaway: Rider's Refactor This command can extract an interface from selected members of a class, generate the interface file, declare that the class implements it, and optionally update existing usages to reference the interface instead.

Prerequisites

• JetBrains Rider installed, recent stable major release. Confirm the build in Help | About before starting.
• A C# solution open in Rider containing the class you want to refactor.
• The class exposes public members (methods, properties, or events) that you want to include in the interface.
• Write permission for the project files and, if applicable, your version-control working directory.

Procedure: extract an interface

1. Open the class. In Solution Explorer, open the C# file that contains the target class.
2. Position the caret. Click inside the class declaration, or select the specific members to include.
3. Open Refactor This. Press Ctrl+Shift+R on Windows or Linux, or Ctrl+T on macOS. You can also right-click the class and choose Refactor This.
4. Choose Extract Interface. From the menu, select Extract Interface.
5. Configure the extraction. In the dialog:
   • Enter an interface name, commonly prefixed with I, such as IOrderProcessor.
   • Select the members to include.
   • Choose where to create the interface file: the same file, a new file, or a specific folder.
   • Decide whether to update usages so existing references target the new interface.
6. Preview and apply. Review the preview pane listing files to be created or modified, then click Next or Apply.

Example configuration

Given a class OrderProcessor with methods Process(Order) and Cancel(int), the dialog might be configured as follows:

Setting	Value
Interface name	IOrderProcessor
Members to extract	Process(Order), Cancel(int)
Destination	New file: IOrderProcessor.cs
Update usages	Yes

After applying, Rider creates IOrderProcessor.cs, changes the class declaration to public class OrderProcessor : IOrderProcessor, and updates selected call sites to use the interface type where the refactoring engine can safely infer it.

Expected checks

1. The new interface file appears in Solution Explorer under the chosen project or folder.
2. The original class declaration includes the interface in its base list.
3. Build the solution. In Rider's integrated terminal (View | Tool Windows | Terminal), at the solution root, run:

   dotnet build '<SolutionName>.sln'

   Where to run: Rider integrated terminal. Permissions: normal file access only. Placeholder: replace <SolutionName> with your solution file name. Expected check: the build completes with no errors. Risk: the command compiles code and does not modify source, but a failed build may indicate that extraction introduced a type mismatch.
4. Open a consumer file that was updated. Verify that variables or parameters now reference the interface rather than the concrete class.

Limitations

• Rider cannot include private members in the extracted interface.
• If the class relies on members not being extracted, the interface may not fully describe its behavior, and some consumers may still need casts to the concrete type.
• Refactoring availability and behavior vary between Rider major releases and .NET SDK versions. Older .NET Framework projects may have limited support.
• Some Rider features require an active license and may be subject to organizational restrictions.

Recovery options

Extract Interface creates and modifies files, so it changes repository state. To undo:

• Press Ctrl+Z on Windows or Linux, or Cmd+Z on macOS, to revert the refactoring through Rider's local history.
• If you already committed, revert the commit or restore affected files from the previous commit in your version-control tool.
• If the build fails after extraction, inspect the refactoring preview, adjust member visibility or interface membership, and repeat the extraction.

Practical verification

Open Help | About and confirm the installed Rider build matches a recent stable release. Then load a C# solution, invoke Refactor This on a method, and confirm the suggested transformation appears and applies without errors before using it on production code.