I would like to parse a date, identified by month and day, into a valid DateTime occurring in the future.

Assume today is 2023-05-06, below is a table of input and output values:

A naive way of achieving this would be to test if using DateTime.Now.Year for the Year portion produces a date in the future or not:

var today = DateTime.Now;
bool dateInFuture = new DateTime(today.Year, 02, 29)).CompareTo(today);

However you might have noticed that this will cause an exception as 2023-02-29 is not a valid date.

Ideally I would like this code to be able to work out if the date is actually invalid, so if 00-46 is passed as input it can tell me that that is not a real date, but that's a little tricky as my current implementation fails with dates that are actually valid.

CodePudding user response：

This may help:

var input = "02-29";
var year = DateTime.Today.Year;
if (DateTime.TryParse($"{year}-{input}", out DateTime date))
{
    var isFutureDate = date > DateTime.Now;
}
else
{
    // TODO: Manage error
}

You can define a method to that:

public static bool TryGetDate(string input, out DateTime date, out bool isFutureDate)
{
    var year = DateTime.Today.Year;
    if (DateTime.TryParse($"{year}-{input}", out date))
    {
        isFutureDate = date > DateTime.Now;
        return true;
    }

    isFutureDate = false;
    return false;
}

And use it:

var input = "02-29";
if (TryGetDate(input, out DateTime date, out bool isFutureDate))
{
    // ...
}
else
{
    // TODO: Manage error
}

CodePudding user response：

You could use DateTime.IsLeapYear(year) - as is shown in this answer in conjuction with DateTime.TryParse for check if the value to convert is a valid DateTime:

You can test this code in dotnetfiddle.net:

DateTime today = DateTime.Now;
Int32 year = DateTime.IsLeapYear(today.Year) ? today.Year : today.AddYears(-2).Year;
DateTime tempDate = DateTime.Now;

if (!DateTime.TryParse(year.ToString()   "/02/29", out tempDate))
{
    // Date is not valid.
    Console.WriteLine("Date ("   year.ToString()   "/02/29"   ") is not valid");
}
else
{
    Console.WriteLine("Date is valid: "   tempDate.ToString("dd/MM/yyyy"));
}