如何使用C＃.net（VS2012）访问另一个项目中的类（但在同一解决方案中）

Question

i am working first time on the three layer architecture, I've created three Projects in one Solution, Project one is named BLL , second is named DAL and third one is names Model , I've Created interface in Model, now want to Create Business Logics in BLL and want to connect it to the DAL where I've connected my Data Base.

For this Purpose I've added Reference of each Project With other like I've Added Reference of BLL in Model and Added reference of BLL in DAL.

now for the time i've created a class is DAL in which i've Connected my DB and have alos Created a Windows Form in Model,

Now my questions are

1)how can I access classes of DAL in BLL and BLL's in Model

2)and which logic I've to create (in BLL) to Access Database through BLL

the class in which I've connected DB is

DB.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient();

namespace WindowsFormsApplication3
{
    class DB
    {
        public void fnc_ConnectoToDB(ref SqlConnection cn)
        {
            string strConnectionString = null;

            strConnectionString = @"Data Source=AHSANMUGHAL;Initial Catalog=SurveyBuilder;User ID=sa;Password=ahsan";

            cn = new SqlConnection();
            cn.ConnectionString = strConnectionString;
            cn.Open();      
        }

        public void fnc_CloseCn(ref SqlConnection cn)
        {
            if (cn.State == ConnectionState.Open == true)
            {
                cn.Close();
            }
        }

    }
}

---

i know this is bit confusing question but I hope you guys will understand it and will ans ASAP

Answer 1

Try to use a dependency injection framework like ninject.

Here is an example:

Your implementation:

public class Samurai {
    public IWeapon Weapon { get; private set; }
    public Samurai(IWeapon weapon) 
    {
        this.Weapon = weapon;
    }
}

And a module to give the Samurai it's weapon:

public class WarriorModule : NinjectModule
{
    public override void Load() 
    {
        this.Bind<IWeapon>().To<Sword>();
    }
}

Simple as that.

Answer 2

first of all, you need to make your class public.

public class DB

Answer 3

Here is a simple example of Dependency Injection based on your classes.

This doesnt utilize any IoC (Inversion of Control) containers that would make your instances easier to manage. I think its easier to conceptualize if you avoid the magic of an IOC container initially. It also makes you glad to have it when you move up that rung.

Ninject is an IoC container mentioned in another answer, Unity is another.

using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Model : Form
    {
        public Model()
        {
            InitializeComponent();
            var bll = new BLL(new DAL());
            bll.WriteToDatabase("mydbvalue");
        }
    }

    public interface IBll
    {
        void WriteToDatabase(string value);
    }
    public class BLL: IBll
    {
        private IDal _dataLayer;
        public BLL(IDal dataLayer)
        {
            _dataLayer = dataLayer;
        }

        public void WriteToDatabase(string value)
        {
            _dataLayer.WriteToDatabase(value);
        }
    }

    public interface IDal
    {
        void WriteToDatabase(string value);
    }
    public class DAL:IDal
    {
        public void WriteToDatabase(string value)
        {
            fnc_ConnectToDB();
        }
    }
}