public static void Main()
{
var InputMonths = new List <string> {
"January", "march", "sepTEmber", "smarch"
};
var MonthNames = new DateTimeFormatInfo().MonthNames.ToList();
var InputMonthNumbers = new List <int>();
foreach (var m in InputMonths)
{
//Find index of the month name, ignoring case
//Note if the input month name is invalid, FindIndex will return 0
int month_num = 1 + MonthNames.FindIndex(name => name.Equals(m, StringComparison.OrdinalIgnoreCase));
if (month_num > 0)
{
InputMonthNumbers.Add(month_num);
}
}
foreach (var n in InputMonthNumbers)
{
Console.WriteLine(n.ToString());
}
}