check if date time string contains time

Question

I have run into an issue. I\'m obtaining a date time string from the database and and some of these date time strings does not contain time. But as for the new requirement every

Answer 1

Here's what I'm going with for now. It may not be perfect, but likely better than considering any 12am datetime as not having a time. The premise is that if I tack a full time specification on the end it will parse if it's just a date but fail if it already has a time component.

I had to make the assumption that there's not some valid, date/time that has 7 non-white-space characters or less. It appears that "1980/10" parses, but not "1980/10 01:01:01.001".

I've included various test cases. Feel free to add your own and let me know if they fail.

public static bool IsValidDateTime(this string dateString, bool requireTime = false)
{
    DateTime outDate;
    if(!DateTime.TryParse(dateString, out outDate)) return false;

    if (!requireTime) return true;
    else
    {
        return Regex.Replace(dateString, @"\s", "").Length > 7 
&& !DateTime.TryParse(dateString + " 01:01:01.001", out outDate);
    }
}

public void DateTest()
{
    var withTimes = new[]{
    "1980/10/11 01:01:01.001",
    "02/01/1980 01:01:01.001",
    "1980-01-01 01:01:01.001",
    "1980/10/11 00:00",
    "1980/10/11 1pm",
    "1980-01-01 00:00:00"};

    //Make sure our ones with time pass both tests
    foreach(var date in withTimes){
        Assert.IsTrue(date.IsValidDateTime(), String.Format("date: {0} isn't valid.", date));
        Assert.IsTrue(date.IsValidDateTime(true), String.Format("date: {0} does have time.", date));
    }

    var withoutTimes = new[]{
    "1980/10/11",
    "1980/10",
    "1980/10 ",
    "10/1980",
    "1980 01",
    "1980/10/11 ",
    "02/01/1980",
    "1980-01-01"};

    //Make sure our ones without time pass the first and fail the second
    foreach (var date in withoutTimes)
    {
        Assert.IsTrue(date.IsValidDateTime(), String.Format("date: {0} isn't valid.", date));
        Assert.IsFalse(date.IsValidDateTime(true), String.Format("date: {0} doesn't have time.", date) );
    }

    var bogusTimes = new[]{
    "1980",
    "1980 01:01",
    "80 01:01",
    "1980T01",
    "80T01:01",
    "1980-01-01T01",
    };

    //Make sure our ones without time pass the first and fail the second
    foreach (var date in bogusTimes)
    {
        DateTime parsedDate;
        DateTime.TryParse(date, out parsedDate);
        Assert.IsFalse(date.IsValidDateTime(), String.Format("date: {0} is valid. {1}", date, parsedDate));
        Assert.IsFalse(date.IsValidDateTime(true), String.Format("date: {0} is valid. {1}", date, parsedDate));
    }
}