Re-factorize a program using single responsibility principle - SOLID- SRP

Question

I am learning SOLID and I am trying to understand the Single Responsibility Principle.

The class WalkingData storages a "date" and a "walked distance". The class also read the stored data.

 public class WalkingData
    {
        public DateTime Date { get; set; }
        public int WalkedDistance { get; set; }
        private string _filePath = @"c:\Data\Json.txt";

        //Read Data from Json File
        public List<WalkingData> GetAll()
        {
            //If file does not exist returns an empty list
            if (!File.Exists(_filePath)) return new List<WalkingData>();

            string jsonData;

            //Read the existing Json file
            using (StreamReader readtext = new StreamReader(_filePath))
            {
                jsonData = readtext.ReadToEnd();
            }

            //Deserialize the Json and returs a list of WalkingData
            return JsonConvert.DeserializeObject<List<WalkingData>>(jsonData);            
        }

        //save an instance of  WalkingData in Json file
        public void Save()
        {
            List<WalkingData> lstExistingWalkingData = new List<WalkingData>();

            //if existing data, load it into lstExistingWalkingData
            if (File.Exists(_filePath))
                lstExistingWalkingData = GetAll();

            //Add the current instace into lstExistingWalkingData
            lstExistingWalkingData.Add(this);

            //Serialize lstExistingWalkingData
            string output = JsonConvert.SerializeObject(lstExistingWalkingData);

            //Save the Json file
            using (StreamWriter w = new StreamWriter(_filePath))
            {
                w.WriteLine(output);
            }
        }      
    }

After I applied the Single Responsabibly Principle I have the new code that I would like to confirm if I applied the principle in a reasonable way:

//This class is located on a library called BOL and has a reference to DAL library
    public class WalkingData
    {
        public DateTime Date { get; set; }
        public int WalkedDistance { get; set; }
    }

    //This class is located on a library called BOL and has a reference to DAL library
    public class WalkingDataManager
    {        
        WalkingDataRepository walkingDataRepository = new WalkingDataRepository();

        public List<WalkingData> GetAll()
        {
            return walkingDataRepository.GetAll();
        }

        public void Save(WalkingData walkingData)
        {
            walkingDataRepository.Save(walkingData);
        }
    }

    //this class is located in library Called DAL
    internal class WalkingDataRepository
    {
        private string _filePath = @"c:\Data\Json.txt";

        //Read Data from Json File
        internal List<WalkingData> GetAll()
        {
            //If file does not exist returns an empty list
            if (!File.Exists(_filePath)) return new List<WalkingData>();

            string jsonData;

            //Read the existing Json file
            using (StreamReader readtext = new StreamReader(_filePath))
            {
                jsonData = readtext.ReadToEnd();
            }

            //Deserialize the Json and returs a list of WalkingData
            return JsonConvert.DeserializeObject<List<WalkingData>>(jsonData);
        }

        //save an instance of  WalkingData in Json file
        internal void Save(WalkingData walkingData)
        {
            List<WalkingData> lstExistingWalkingData = new List<WalkingData>();

            //if existing data, load it into lstExistingWalkingData
            if (File.Exists(_filePath))
                lstExistingWalkingData = GetAll();

            //Add the current instace into lstExistingWalkingData
            lstExistingWalkingData.Add(walkingData);

            //Serialize lstExistingWalkingData
            string output = JsonConvert.SerializeObject(lstExistingWalkingData);

            //Save the Json file
            using (StreamWriter w = new StreamWriter(_filePath))
            {
                w.WriteLine(output);
            }
        }
    }

Answer 1

You separated the responsibility of saving data (WalkingDataRepository) and also encapsulated it within WalkingDataManager. The refactoring work totally aligns with what SRP says. In short, the SRP is not just about breaking down the functionalities but also about encapsulating them! I also wrote an article about it.

What bothers me is the anemic WalkingData model. This is an anti-pattern. You should rather let WalkingData handle the responsibility of maintaining its own data rather than creating another class WalkingDataManager to do that job.