Algorithm of the middle point (2D Bresenham) to draw a line, where points are printing in console.

bresenham.cs

/// <summary>
/// Algorithm of the middle point, where points are printing in console
/// Works independently of the position of both points. Also is more easy using Point from Drawing.
/// </summary>
/// <param name="x1">X value of the 1st point</param>
/// <param name="y1">Y value of the 1st point</param>
/// <param name="x2">X value of the 2nd point</param>
/// <param name="y2">Y value of the 2nd point</param>
static void Bresenham(int x1, int y1, int x2, int y2)
{
  int incCase1 = 0, incCase2 = 0;
  int x, y, addX1 = 0, addY1 = 0, addX2 = 0, addY2 = 0, dx, dy;
  int d = 0;

  if (x1 > x2)  //swapping in case of 1st is bigger than 2nd
  {
    int tx, ty;
    tx = x1;  //x1 ^= x2; x2 ^= x1; x1 ^= x2; 
    x1 = x2;
    x2 = tx;

    ty = y1;  //y1 ^= y2; y2 ^= y1; y1 ^= y2; 
    y1 = y2;
    y2 = ty;
  }

  dx = x1 - x2; dy = y1 - y2;
  x = x1; y = y1;

  if (dy == 0)  //horizontal line
  {
    for (int i = x; i <= x2; i++)
      Console.WriteLine("("+i+","+y+")");
    return;
  }

  if (dx == 0)  //vertical line
  {
    for (int i = Math.Min(y1, y2); i <= Math.Max(y1, y2); i++)
      Console.WriteLine("(" + x + "," + i + ")");
    return;
  }

  //slope between [0 - 1]
  if ((dy >= dx) && (dy <= 0))
  {
    incCase1 = dy * 2; // dy << 1;
    incCase2 = incCase1 - (dx * 2);  //(dx << 1);
    d = incCase1 - dx;
    addX1 = 1;
    addX2 = 1;
    addY2 = 1;
  }

  //slope 1 - +infi
  else if (dx > dy)
  {
    incCase2 = -dx * 2;// dx << 1;
    incCase1 = dy * 2 + incCase2; // (dy << 1) + incCaso2;
    d = dy * 2 - dx; //(dy << 1) - dx;
    addX1 = 1;
    addY1 = 1;
    addY2 = 1;
  }

  //slope 0 - -1
  else if ((dy > 0) && (-dx >= dy))
  {
    incCase2 = dy * 2; // dy << 1;
    incCase1 = incCase2 + dx * 2; // (dx << 1);
    d = incCase2 + dx;
    addX1 = 1;
    addY1--;
    addX2 = 1;
  }

  //slope between -inf - -1
  else if (-dx < dy)
  {
    incCase1 = dx * 2;  //dx << 1;
    incCase2 = (dy * 2) + incCase1; ;  // (dy << 1) + incCase1;
    d = (dy * 2) + dx; // (dy << 1) + dx;
    addY1--;
    addX2 = 1;
    addY2--;
  }

  //any line
  while (x < x2)
  {
    Console.WriteLine("(" + x + "," + y + ")");
    if (d >= 0)
    {
      d += incCase1;
      x += addX1;
      y += addY1;
    }
    else
    {
      d += incCase2;
      x += addX2;
      y += addY2;
    }
  }
  Console.WriteLine("(" + x2 + "," + y2 + ")");
}