Произведение положительных элементов массива

int[] arr = new[] { ... };
int prod = 1;
foreach (var i in arr) if (i > 0) prod *= i;
Console.WriteLine(prod);

int[] arr = new[] { ... };
int mi = 0;
for (int i = 0; i < arr.Length; ++i) if (arr[i] < arr[mi]) mi = i;
int sum = 0;
for (int j = 0; j < mi; ++j) sum += arr[j];
Console.WriteLine(sum);

int[,] mx = new[,] { ... };
int count = 0;
for (int i = 0; i < mx.GetLength(0); ++i)
{
  int rcount = 0;
  bool hasZero = false;
  for (int j = 0; j < mx.getLength(1); ++j)
  {
     hasZero = mx[i, j] == 0;
     rcount += mx[i, j] < 0 ? 1 : 0;
  }
  if (hasZero) count += rcount;
}
Console.WriteLine(count);

static bool isSaddle(int[,] mx, int i, int j)
{
   int mi = 0, mj = 0;
   for (int i0 = 0; i0 < mx.GetLength(0); ++i0) if (mx[i0, j] < mx[mi, j]) mi = i0;
   for (int j0 = 0; j0 < mx.GetLength(1); ++j0) if (mx[i, j0] < mx[i, mj]) mj = j0;
   return i == mi && j == mj;
}
//...
int[,] mx = new[,] { ... };
for (int i = 0; i < mx.GetLength(0); ++i)
  for (int j = 0; j < mx.getLength(1); ++j)
    if(isSaddle(mx, i, j)) Console.WriteLine("[{0}; {1}] - Saddle point", i, j);

using System;
 
public class Point
{
    private int red;
    private int green;
    private int blue;
 
    public Point() { }
 
    public Point(double x, double y)
        : this(x, y, 0) { }
 
    public Point(double x, double y, int rgb)
    {
        if (rgb < 0 || rgb > 0xFFFFFF)
            throw new Exception("Неверно задан цвет.");
        this.X = x;
        this.Y = y;
        this.red = (rgb & 0xFF0000) >> 16;
        this.green = (rgb & 0xFF00) >> 8;
        this.blue = rgb & 0xFF;
    }
 
    public Point(double x, double y, int red, int green, int blue)
    {
        ChangeColor(red, green, blue);
        this.X = x;
        this.Y = y;
    }
 
    public Point(Point other)
        : this(other.X, other.Y, other.red, other.green, other.blue) { }
 
    public double X { get; set; }
    public double Y { get; set; }
 
    public int Red { get { return red; } }
    public int Green { get { return green; } }
    public int Blue { get { return blue; } }
 
    public void ChangeColor(int red, int green, int blue)
    {
        if (!Check(red) || !Check(green) || !Check(blue))
            throw new Exception("Неверно задан цвет.");
        this.red = red;
        this.green = green;
        this.blue = blue;
    }
 
    private bool Check(int value)
    {
        return value >= 0 && value <= 255;
    }
}