Question

I’m trying to create a basic unit of work to fully understand the principles. I can re-factor later. I’m simply trying to get it working. I’m having some trouble.

I have a simple entity Code:

public class Code
{
    public int Id { get; set; }
    public string Type { get; set; }
    public string Value { get; set; }
    public string Description { get; set; } 
}

I have a CodeRepository with one simple Method.

public class CodeRepository
    {
        public Code GetByCode(string value)
        {
            // Go to DB and find code. Just using a sample.
            var code = new Code();
            code.Type = "Dx";
            code.Value = "20";
            return code;
        }
    }

I have a simple UnitOfWork class:

public class UnitOfWork
{
    private CodeRepository _codeRepository;
    public CodeRepository CodeRepository
    {
        get
        {
            if (_codeRepository == null)
                _codeRepository = new CodeRepository();
            return _codeRepository;
        }
    }

    public void Commit()
    {

    }

    public void Rollback()
    {

    }
} 

If I wanted to use the UnitOfWork to call my repository and get a code by name, I’d do:

var uow = new UnitOfWork();
var code = uow.CodeRepository.GetByCode("x");

Where is the connection created to use? I’m uncertain where I need to go next. Also have to use ADO.NET.

Update
Many of the folks below say that the connection should be opened in the repository. If for example, I needed to call 3 different GetBy methods in 3 separate repositories to get values for a view, would I want to open a new connection each time? Or, can I open a single connection?

Answer 1

I would create, open, use and close the connection at the last point where you actually retrieve it from the database, hence in GetByCode

public Code GetByCode(string value)
{
    // Go to DB and find code. Just using a sample.
    // assuming SqlConnection, store the connection-string f.e. in the settings
    string sql = "SELECT Columns FROM dbo.Table Where Value=@Value";
    using(var con = new SqlConmection(connectionString))
    using(var cmd = new SqlCommand(sql, con))
    {
        cmd.Parameters.AddWithValue("@Value", value);
        con.open();
        using(var reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                Code code = new Code();
                // initiliaze it from the reader, f.e.
                code.Id = reader.GetInt32(reader.GetOrdinal("Id"));
            }
        }
    }
}

`