Почему выдает предупреждения? - C#

/*
 * Created by SharpDevelop.
 * User: 26-60-911
 * Date: 13.08.2017
 * Time: 20:58
 * 
 * To change this template use Tools | Options | Coding | Edit Standard Headers.
 */
using System;
 
namespace Алгоритм_Брезенхема
{
    class Program
    {
        public static void Main(string[] args)
        {
            Console.Title = "Console";
            
            int x = 10;
            int y = 10;
            int x1 = 30;
            int y1 = 20;
            
            int incX, incY;
            int errorX, errorY;
            int currentX, currentY;
            
            int dx = x1 - x;
            int dy = y1 - y;
            
            if (dx > 0) { incX = 1; }
            else { if (dx == 0) { incX = 0; } else { incX = -1; }}
            
            if (dy > 0) { incY = 1; }
            else { if (dy == 0) { incY = 0; } else { incY = -1; }}
            
            dx = System.Math.Abs(dx);
            dy = System.Math.Abs(dy);
            
            int L = System.Math.Max(dx, dy);
            
            errorX = x;
            errorY = y;
            
            currentX = x;
            currentY = y;
            
            while ((currentX != x1) || (currentY != y1))
            {
                errorX += dx;
                errorY += dy;
                
                System.Console.SetCursorPosition(currentX, currentY);
                System.Console.Write('X');
                
                if (errorX > L)
                {
                    errorX -= L;
                    currentX += 1;
                }
                
                if (errorY > L)
                {
                    errorY -= L;
                    currentY += 1;
                }
            }
            
            Console.ReadKey(true);
        }
    }
}