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RegEx for yyyyMMdd format

Posted on 2010-09-14
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Last Modified: 2013-12-16
I have a csv file that has a date column in the following format yyyyMMdd
eg:- 20011114

i want to parse this date via a RegEx into a format that is acceptable by DateTime class in C#

this is what i have done so far (see code section below)

however i am getting an error "Input string was not in a correct format" when the code enters the following line.


if (!ConvertToDate(int.Parse(m.Groups["year"].Value), int.Parse(m.Groups["month"].Value), int.Parse(m.Groups["day"].Value), out date))



m = Regex.Match(str, @"(?<=^(([2-9]\d{3}|1999)((0[1-9]|1[012])(0[1-9]|1\d|2[0-8])|(0[13456789]|1[012])(29|30)|(0[13578]|1[02])31)|(([2-9]\d)(0[48]|[2468][048]|[13579][26])|(([2468][048]|[3579][26])00))0229)$)", RegexOptions.Compiled | RegexOptions.IgnoreCase);
            if (m.Success)
            {
                DateTime date;
                if ((defaultFormat ^ DateTimeFormat.USA_DATE) == DateTimeFormat.USA_DATE)
                {
                    if (!ConvertToDate(int.Parse(m.Groups["year"].Value), int.Parse(m.Groups["day"].Value), int.Parse(m.Groups["month"].Value), out date))
                        return false;
                }
                else
                {
                    if (!ConvertToDate(int.Parse(m.Groups["year"].Value), int.Parse(m.Groups["month"].Value), int.Parse(m.Groups["day"].Value), out date))
                        return false;
                }
                parsedDate = new ParsedDateTime(m.Index, m.Length, -1, -1, date);
                return true;

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Question by:2ooth
6 Comments
 
LVL 40

Expert Comment

by:Gurvinder Pal Singh
ID: 33670084
Assuming that month and date starts from 0
[0-9]{1,4}([0][0-9]|[1][0-2])([0-2][0-9]|[3][0-1])
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LVL 40

Assisted Solution

by:Gurvinder Pal Singh
Gurvinder Pal Singh earned 1000 total points
ID: 33670103
or just this
Dim D As Date = Date.ParseExact(X, "yyyyMMdd", Nothing);
from here
http://bytes.com/topic/visual-basic-net/answers/616836-type-conversion-date-formatted-yyyymmdd


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LVL 13

Expert Comment

by:Naman Goel
ID: 33670128
You can refer to following link
 
http://www.codeproject.com/KB/recipes/RegexTester.aspx 
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LVL 10

Accepted Solution

by:
Mathiyazhagan earned 1000 total points
ID: 33670355
I too suggest you to go with DateTime functions as it assures valid date. you can do it with TryParseExact method and  cultureInfo.have attched sample code; hope this helps.
private bool GetValidDate(string str,bool IsUSCulture,out DateTime date)
        {
            System.Globalization.CultureInfo culture = System.Globalization.CultureInfo.InvariantCulture;
            if (IsUSCulture)
                culture = new System.Globalization.CultureInfo("en-US");
            return DateTime.TryParseExact(str, "yyyyMMdd", culture , System.Globalization.DateTimeStyles.None, out date);
        }

//using the above code

 DateTime d;
            if (GetValidDate("20011114", true , out d))
            { 
                //work with valid date d
            }

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LVL 75

Expert Comment

by:käµfm³d 👽
ID: 33672047
I also agree that you should use the Parse group of methods which are members of the DateTime struct.
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Author Closing Comment

by:2ooth
ID: 33679998
Thanks Guys!!!
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