Checking string in the particular time format

Question

I'm trying check is string(textBox1.Text) on the time format "hh:mm:ss", for send that string, as time parameter, in Sql query. I use TimeSpan.TryParseExact method:

        TimeSpan check;
        TimeSpan.TryParseExact(textBox1.Text, "hh:mm:ss", null, out check);
        if(check==null)   MessageBox.Show("incorrect time");
        else... 

But when I write to textbox 11 to the table adding the time 00:00:11 (11 seconds). I want so it's was incorrect time, correct is 00:00:11 line. How to do it's right?

Answer 1

You should use controls that are suitable for the task you're trying to do. For example, in this case, it may be easier and more consistent for users to use a DateTimePicker control instead of a TextBox.

Set the DateTimePicker's Format property to Time and the ShowUpDown property to true. You can also do this in code as shown below.

myTimePicker.Format = DateTimePickerFormat.Time;
myTimePicker.ShowUpDown = true;

You can also use the CustomFormat property to format the way you want the time displayed. If you use CustomFormat, you'll want to do this:

myTimePicker.Format = DateTimePickerFormat.Custom; //instead of Time as above
myTimePicker.CustomFormat = "hh:mm:ss"; //or whichever format you want

Answer 2

You should change your code to use the result of TryParseExact that is a boolean true if the conversion succed. Also notice that there is a standard format string for hours/minutes/seconds

TimeSpan check;
if(TimeSpan.TryParseExact("09:00:01", "g", CultureInfo.CurrentCulture, out check))
    MessageBox.Show("Correct");
else
    MessageBox.Show("Incorrect");

EDIT
Looking at your comment below then probably you need a custom timespan format string

TimeSpan check;
if(TimeSpan.TryParseExact("09:00:01", @"hh\:mm\:ss", CultureInfo.CurrentCulture, out check))
    MessageBox.Show("Correct");
else
    MessageBox.Show("Incorrect");

Answer 3

You could do this using regular expressions:

using System.Text.RegularExpressions;
namespace StackOverflow
{
    class Demo
    {
        /* ... */
        readonly Regex timeFormat = new Regex(@"^(?:(?:[0-1][0-9])|2[0-3]):[0-5][0-9]:[0-5][0-9]$", RegexOptions.Compiled);
        public bool IsTimeFormatValid(string time)
        {
            return timeFormat.IsMatch(time);
        }
        /* ... */
    }
}

Regex Example: http://regex101.com/r/qR3qV6/1

NB: Timespan.TryParse aims to convert a string to a timespan. TryParseExact does the same; only it allows you to specify a culture/expected format (it's poorly named as it doesn't force the format to be exactly what you've specified).

These methods want to convert if possible; so they're quite generous in what they'll accept. They're not designed to validate the format; only to make a best attempt at converting the given data based on a given format. In this case given a string lacking information they're assuming that hours and minutes not being specified means they're 0 valued, so they treat your data as seconds.

Using a regex avoids this issue - it says you want to check the format rather than just see if the system can make a guess at what the data in that format means.