Is BaseClass is allowed in strategy pattern

I have created a solution to read/process various kinds of files, e.g. XML, JSON, txt.

public interface IFileProcessor
{
     TOutput Process<TInput, TOutput>(TInput input);
}

public abstract class FileProcessorBase
    {
        protected readonly FileInfo fileInfo;
        protected FileProcessorBase(FileInfo fileInfo)
        {
            this.fileInfo = fileInfo;
        }

        protected abstract TOutput Load<TOutput>();
    }

And the concrete class as follows.

public class JsonFileProcessor : FileProcessorBase, IFileProcessor
    {
        public JsonFileProcessor(FileInfo fileInfo) : base(fileInfo) 
        {

        }
        public TOutput Process<TInput, TOutput>(TInput from)
        {
              //Call Load Method
              Load<string>();
        }

        protected override TOutput Load<TOutput>()
        {
              string res = "JSON Load method";
              return (TOutput)Convert.ChangeType(res, typeof(TOutput), CultureInfo.InvariantCulture);
        }
  }

and now this is factory class

public class FileProcessorFactory
    {
        static readonly Dictionary<string, IFileProcessor> fileProcessor;
        static FileProcessorFactory()
        {
            fileProcessor = new Dictionary<string, IFileProcessor>();
            fileProcessor.Add("XML", new XMLFileProcessor(new FileInfo(""));
            fileProcessor.Add("JSON", new JsonFileProcessor(new FileInfo(""));
        }

        public static IFileProcessor GetFileProcessor(string key)
        {
            return fileProcessor[key];
        }
    }

Below is FileProcessorService class

public class FileProcessorService
    {
        IFileProcessor fileProcessor;

        public FileProcessorService(IFileProcessor fileProcessor)
        {
            this.fileProcessor = fileProcessor;
        }

        public TOutput Process<TInput, TOutput>(TInput from)
        {
            return fileProcessor.Process<TInput, TOutput>(from);
        }
    }

Now Finally, I'm calling through this way.

IFileProcessor fileProcessor = FileProcessorFactory.GetFileProcessor("XML");
FileProcessorService fileProcessorService = new FileProcessorService(fileProcessor);
var XMLResult = fileProcessorService.Process<string, string>("");

Can I use base class in strategy pattern?