Dependency Injection Pattern (Loose Coupling)

using System;
using System.Collections.Generic;
using System.Text;

namespace Dependency.Injection.InterfaceInjection
{
	public interface IFarm
	{
		//This method calculate number of farmers
		//needed to take care of the animals in the farm
		int NumberOfFarmers(int numberOfAnimals);

		//This method calculate the area of farm
		//needed to hold a given number of animals
		double LandInAcres(int numberOfAnimals);

	}

	public interface IFarmFacade
	{
		//This method calculate number of farmers
		//needed to take care of the animals in the farm
		void SetFarmObject(IFarm farm);



	}

	class CowFarm : IFarm
	{
		#region "Constants"

		int COW_PER_FARMER = 10;
		int COW_IN_ACRE = 25;
		int DEFAULT_NUM_OF_FARMERS = 1;

		#endregion

		#region "Methods"

		public int NumberOfFarmers(int numberOfAnimals)
		{
			int farmers = DEFAULT_NUM_OF_FARMERS;
			if (numberOfAnimals > COW_PER_FARMER)
				farmers = (int)(numberOfAnimals / COW_PER_FARMER);

			return farmers;
		}

		public double LandInAcres(int numberOfAnimals)
		{
			double acres = 1.0;
			if (numberOfAnimals > COW_IN_ACRE)
				acres = numberOfAnimals / COW_IN_ACRE;

			return acres;
		}
		#endregion
	}


	class SheepFarm : IFarm
	{
		#region "Constants"

		int SHEEP_PER_FARMER = 40;
		int SHEEP_IN_ACRE = 100;
		int DEFAULT_NUM_OF_FARMERS = 1;

		#endregion

		#region "Methods"

		public int NumberOfFarmers(int numberOfAnimals)
		{
			int farmers = DEFAULT_NUM_OF_FARMERS;
			if (numberOfAnimals > SHEEP_PER_FARMER)
				farmers = (int)(numberOfAnimals / SHEEP_PER_FARMER);

			return farmers;
		}

		public double LandInAcres(int numberOfAnimals)
		{
			double acres = 1.0;
			if (numberOfAnimals > SHEEP_IN_ACRE)
				acres = numberOfAnimals / SHEEP_IN_ACRE;

			return acres;
		}

		#endregion
	}



	public class FarmFacade
	{
		private IFarm currentFarm;

		public void SetFarmObject(IFarm farm)
		{  
			//interface injection
			currentFarm = farm;
		}

		public double TotalCost(int numberOfAnimals)
		{

			return ((50000 * currentFarm.NumberOfFarmers(numberOfAnimals)) + (100000 * currentFarm.LandInAcres(numberOfAnimals)));
		}

	}
}