C#

public static TheWeather GetAverageForMonth(List<TheWeather> entries, int year, int month)
{
    if (entries == null || entries.Count < 1)
    {
        return null;
    }
    int days = 0;
    int index = entries.Count();
    double total = 0.0;
    double Aveg = 0.0;

    for (index = 0; index < entries.Count; index++)
    {
        // this is your fix
        if (entries[index].dateTime.Year == year 
            && entries[index].dateTime.Month == month 
            // add this line so that it won't include an item without a value
            && entries[index].Actual_mean_temp > 0)
        {
            total += entries[index].Actual_mean_temp;
            // add the "+" to your operator, and only add 1
            days += 1;
        }
    }

    Aveg = total / days;
    return entries[index];
}

days += 1;    // it's just a count of the valid temperature entries

days++;

days = days + 1;

Quote:

#realJSOP

average = sum of samples / number of samples

#realJSOP wrote:

say out loud, "Alexa, I've detected an advertisement".

using System;
using System.Collections.Generic;
					
public class Program
{
	public class TheWeather
    {
        public DateTime dateTime { get; set; } // WHY?? give it a decent name,
                                               // don't use the type-name
        public double Actual_mean_temp { get; set; }
        public double Record_min_temp { get; set; }
        public double Record_max_temp { get; set; }
        public double Actual_precipitation { get; set; }

    }
	public static TheWeather GetAverageForMonth(List<TheWeather> entries, int year, int month)
    {
        TheWeather GetItem = entries[0]; // .First();

        return GetItem;
    }
	public void Main()
	{
		List<TheWeather> wl = new List<TheWeather>();
		wl.Add(new TheWeather() {Actual_mean_temp = 10});
		wl.Add(new TheWeather() {Actual_mean_temp = 20});
		
		double sum = 0; int cnt = 0;
		for (cnt = 0; cnt < wl.Count ; cnt++)
		{
			sum += wl[cnt].Actual_mean_temp;
			Console.WriteLine(string.Format("item {0}, new avg: {1}", cnt, sum / (cnt + 1)));
		}
	}
}

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

Abdalla Ben Omran wrote:

with LINQ its always easy to get a solution thus i am trying to use no LINQ just for excerices

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.