C#, you can extract files or folders from a RAR archive using the System.Diagnostics.Process class to execute the WinRAR command-line tool. 

the ExtractFromRar() method takes three string arguments: inputPath, which is the path to the RAR archive to extract, outputPath, which is the path of the output folder, and password, which is an optional password to unlock the archive. The winrarPath variable defines the path to the WinRAR executable, which must be installed on your system. The arguments variable defines the command-line arguments to pass to the WinRAR executable to extract the archive, which include the input path, output path, and password (if specified).

The ProcessStartInfo class is used to define the start information for the WinRAR process, including the executable path, command-line arguments, and other options such as hiding the window. The Process class is used to start the WinRAR process, wait for it to finish, and obtain its exit code.