Repository and Data Mapper pattern

After a lots of read about Repository and Data Mapper I decided to implement those patterns in a test project. Since I'm new to these I'd like to get your views about how did I implement those in a simple project.

Jeremy Miller says :

Do some sort of nontrivial, personal coding project where you can freely experiment with design patterns.

But I don't know I did all this things right or not.

Here is my project structure :

enter image description here

As you can see there are many folders which I'm going to describe them in detail in below.

Domain : Project Domain Entities go here I've a simple Personnel class which is inherited from EntityBase class, EntityBase class has a single property named Id.
```
public int Id { get; set; }
```
Infrustructure : Here is a simple Data Access Layer with two classes. SqlDataLayer is a simple class which is inherited from an abstract class named DataLayer. Here I provide some functionality like following code :
```
public SQLDataLayer() {
    const string connString = "ConnectionString goes here";
    _connection = new SqlConnection(connString);
    _command = _connection.CreateCommand();
}
```

adding parameter to commands parameter collection :

    public override void AddParameter(string key, string value) {
        var parameter = _command.CreateParameter();
        parameter.Value = value;
        parameter.ParameterName = key;

        _command.Parameters.Add(parameter);
    }

executing DataReader :

    public override IDataReader ExecuteReader() {
        if (_connection.State == ConnectionState.Closed)
            _connection.Open();

        return _command.ExecuteReader();
    }

and so on.

Repository : Here I tried to implement repository pattern. IRepository is a generic interface

IRepository.cs :

public interface IRepository<TEntity> where TEntity : EntityBase
{
    DataLayer Context { get; }

    TEntity FindOne(int id);
    ICollection<TEntity> FindAll();

    void Delete(TEntity entity);
    void Insert(TEntity entity);
    void Update(TEntity entity);
}

Repository.cs :

public class Repository<TEntity> : IRepository<TEntity> where TEntity : EntityBase, new() {
    private readonly DataLayer _domainContext;
    private readonly DataMapper<TEntity> _dataMapper;
    public Repository(DataLayer domainContext, DataMapper<TEntity> dataMapper) {
        _domainContext = domainContext;
        _dataMapper = dataMapper;
    }
    public DataLayer Context {
        get { return _domainContext; }
    }
    public TEntity FindOne(int id)
    {
        var commandText = AutoCommand.CommandTextBuilder<TEntity>(CommandType.StoredProcedure, MethodType.FindOne);

        // Initialize parameter and their types
        Context.AddParameter("Id", id.ToString(CultureInfo.InvariantCulture));
        Context.SetCommandType(CommandType.StoredProcedure);
        Context.SetCommandText(commandText);

        var dbReader = Context.ExecuteReader();
        return dbReader.Read() ? _dataMapper.Map(dbReader) : null;
    }

I didn't expose not implemented methods from IRepository.

Here in Generic Repository class I expect two parameters in constructor first is a reference to my SqlDataLayer class and second is a reference to Entity DataMapper. Those parameters sent by each Entities Repository class which inherited from Repository class. for example :

public class PersonnelRepository : Repository<Personnel>, IPersonnelRepository {
    public PersonnelRepository(DataLayer domainContext, PersonnelDataMapper dataMapper)
        : base(domainContext, dataMapper) {

    }
}

As you can see here in the FindOne method I tried to automate some operation such as creating CommandText, then I took the advantage of my DataLayer class to configure command and finally execute command to get IDataReader. I pass IDataReader to my DataMapper class to map to the Entity.

DomainMapper : Finally here I map result of IDataReader to Entities, bellow is a sample of how I map Personnel entity :

public class PersonnelDataMapper : DataMapper<Personnel> {
public override Personnel Map(IDataRecord record) {
    return new Personnel {
        FirstName = record["FirstName"].ToString(),
        LastName = record["LastName"].ToString(),
        Address = record["Address"].ToString(),
        Id = Convert.ToInt32(record["Id"])
    };
}}

Usage :

    using (var context = new SQLDataLayer()) {
        _personnelRepository = new PersonnelRepository(context, new PersonnelDataMapper());
            var personnel  = _personnelRepository.FindOne(1);
    }

I know I did many mistake here, that's why I'm here. I need your advice to know what I did wrong or what are the good points in this simple test project.

Thanks in advance.

public override IDataReader ExecuteReader(Command command, ref SqlTransaction transaction) { SqlConnection connection = null; if (transaction == null) { connection = new SqlConnection(connString); transaction = connection.BeginTransaction(); } else { connection = transaction.Connection; } command.Connection = connection; return command.ExecuteReader(); } // When you call this, you can pass along a transaction by reference. If it is null, a new one will be created for you, and returned via the ref parameter for re-use in your next call: SqlTransaction transaction = null; // This line sets up the transaction and executes the first command var myFirstReader = mySqlDataLayer.ExecuteReader(someCommandObject, ref transaction); // This next line gets executed on the same transaction as the previous one. var myOtherReader = mySqlDataLayer.ExecuteReader(someOtherCommandObject, ref transaction); // Be sure to commit the transaction afterward! transaction.Commit(); // Be a good kid and clean up after yourself transaction.Connection.Dispose(); transaction.Dispose();

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