Tuesday, April 12, 2011

DateTime.Parse problem

Some of DateTime are taken from the user input and they are instantiated by the simaple DateTime constructor new DataTime(year, month, day);. When they are serialized into XML, the string will become like this:


I tried to parse it back to DateTime from a XML value string. Unfortunately, I tried every method I know but kept getting String was not recognized as a valid DateTime error. For example,

    // Every method here causes String was not recognized as a valid DateTime error.  
    DateTime d = DateTime.Parse(query.Element("joinDate").ToString());
    string dateStr = query.Element("joinDate").ToString().Replace("T", "");
    DateTime d = XmlConvert.ToDateTime(dateStr, "yyyy-mm-dd hh:mm:ss");
    string dateStr = query.Element("joinDate").ToString().Replace("T", "");
    DateTime d = DateTime.ParseExact(dateStr, "yyyy-mm-dd hh:mm:ss", null);  
    string dateStr = query.Element("joinDate").ToString().Replace("T00:00:00", "");
    DateTime d = DateTime.ParseExact(dateStr, "yyyy-mm-dd", null);   

None of the above work for me. I also tried to follow the example/best practice discussed in MSDN but the error won't go away. Timezone is not my concern. As a matter of fact, my serialized XML value is not really represented in UTC time ( 2001-07-08T00:00:00 ). I guess it may be why MSDN suggestion won't work!

I finally gave up trying and use Regular Expression to parse the date fields and then convert it to DateTime manually. The following is my solution. I am sure that there is a better way to handle it but I just don't know how and probably I don't understand how the DataTime.Parse works!

// Manually parse the string to DateTime

string pattern = @"(?\d{4})-(?\d{2})-(?\d{2})T00:00:00";
System.Text.RegularExpressions.Match m = 
System.Text.RegularExpressions.Regex.Match(query.Element("joinDate").ToString(), pattern);
int year = int.Parse(m.Groups["year"].ToString());
int month = int.Parse(m.Groups["mth"].ToString());
int day = int.Parse(m.Groups["day"].ToString());

// this statement is also exactly how 
// I create the DateTime from the user's input.
DateTime d = new DateTime(year, month, day); 

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