[c#] DateTime.Compare how to check if a date is less than 30 days old?

I'm trying to work out if an account expires in less than 30 days. Am I using DateTime Compare correctly?

if (DateTime.Compare(expiryDate, now) < 30)

{
     matchFound = true;
}

Assuming you want to assign false (if applicable) to matchtime, a simpler way of writing it would be..

matchtime = ((expiryDate - DateTime.Now).TotalDays < 30);

Compare is unnecessary, Days / TotalDays are unnecessary.

All you need is

if (expireDate < DateTime.Now) {
    // has expired
} else {
    // not expired
}

note this will work if you decide to use minutes or months or even years as your expiry criteria.

No you are not using it correctly.

See here for details.

DateTime t1 = new DateTime(100);
DateTime t2 = new DateTime(20);

if (DateTime.Compare(t1, t2) >  0) Console.WriteLine("t1 > t2"); 
if (DateTime.Compare(t1, t2) == 0) Console.WriteLine("t1 == t2"); 
if (DateTime.Compare(t1, t2) <  0) Console.WriteLine("t1 < t2");

Actually none of these answers worked for me. I solved it by doing like this:

  if ((expireDate.Date - DateTime.Now).Days > -30)
  {
    matchFound = true;
  }

When i tried doing this:

matchFound = (expiryDate - DateTime.Now).Days < 30;

Today, 2011-11-14 and my expiryDate was 2011-10-17 i got that matchFound = -28. Instead of 28. So i inversed the last check.

You can try to do like this:

var daysPassed = (DateTime.UtcNow - expiryDate).Days;
if (daysPassed > 30)
{ 
    // ...
}

What you want to do is subtract the two DateTimes (expiryDate and DateTime.Now). This will return an object of type TimeSpan. The TimeSpan has a property "Days". Compare that number to 30 for your answer.

No, the Compare function will return either 1, 0, or -1. 0 when the two values are equal, -1 and 1 mean less than and greater than, I believe in that order, but I often mix them up.

This will give you accurate result :

if ((expiryDate.Date - DateTime.Now.Date).Days < 30)
    matchFound = true;

No it's not correct, try this :

DateTime expiryDate = DateTime.Now.AddDays(-31);
if (DateTime.Compare(expiryDate, DateTime.Now.AddDays(-30)) < 1)
{
    matchFound = true;
}

Try this instead

if ( (expiryDate - DateTime.Now ).TotalDays < 30 ) { 
  matchFound = true;
}

// this isn't set up for good processing.  
//I don't know what data set has the expiration 
//dates of your accounts.  I assume a list.
// matchfound is a single variablethat returns true if any 1 record is expired.

bool matchFound = false;
            DateTime dateOfExpiration = DateTime.Today.AddDays(-30);
            List<DateTime> accountExpireDates = new List<DateTime>();
            foreach (DateTime date in accountExpireDates)
            {
                if (DateTime.Compare(dateOfExpiration, date) != -1)
                {
                    matchFound = true;
            }
            }

should be

matchFound = (expiryDate - DateTime.Now).TotalDays < 30;

note the total days otherwise you'll get werid behaviour

Compare returns 1, 0, -1 for greater than, equal to, less than, respectively.

You want:

    if (DateTime.Compare(expiryDate, DateTime.Now.AddDays(30)) <= 0) 
    { 
        bool matchFound = true;
    }

Well I would do it like this instead:

TimeSpan diff = expiryDate - DateTime.Today;
if (diff.Days > 30) 
   matchFound = true;

Compare only responds with an integer indicating weather the first is earlier, same or later...