Max Method Implementation

[__DynamicallyInvokable]

//The object, calling this method, is passed as an argument,
// although this is not visible when we use code.
public static int Max(this IEnumerable<int> source)
{
    if (source != null)
    {
        int num = 0;
        bool flag = false;
        foreach (int num1 in source)
        {
            if (!flag)
            {
                num = num1;
                flag = true;
            }
            else
            {
        //Key moment
        //----------------
                if (num1 <= num) //Here, the tested value must be greater than current max value.
                {
                    continue;
                }
                num = num1;
        //--------------------------
            }
        }
        if (!flag)
        {
            throw Error.NoElements();
        }
        else
        {
            return num;
        }
    }
    else
    {
        throw Error.ArgumentNull("source");
    }
}