Develop Reference

DateTime Format provider for filepath

I have a file-path that's been created from DateTime stamp:
"C:\\Logs\\Tests\\2015\\Mar\\24\\13_32_09\"
Now I am trying to convert my file-path back to DateTime object.
With Regex I can easily remove "C:\\Logs\\Tests\", but now I am assume I need to provide implementation of IFormtProvider to convert 2015\\Mar\\24\\13_32_09\ into a DateTime object, but I haven't come along any similar example of how that's usually done.
Any example, may not be particular solution to my answer, would be helpful.
Thanks

You can use DateTime.ParseExact like:
DateTime dt = DateTime.ParseExact("2015\\Mar\\24\\13_32_09\\",
#"yyyy\\MMM\\dd\\HH_mm_ss\\",
CultureInfo.InvariantCulture);

No, you don't need to create an IFormatProvider at all. The invariant culture is fine for this (assuming the month name is always in English). You can just use DateTime.ParseExact, passing in the appropriate custom format string (quoting the literal characters, either with apostrophes around them or backslashes before them):
var dateTime = DateTime.ParseExact(
text,
#"yyyy'\'MMM'\'dd'\'HH'_'mm'_'ss'\'",
CultureInfo.InvariantCulture);
Note that this assumes the path really does use backslashes... it won't work on Unix as-is. (You might want to canonicalize the directory separators first.)

DateTime.ToString() not working as expected

In the screenshot DateTime.ToString() method is being called but the date is not getting formatted in expected format (as seen in Quick Watch widnow). Is something wrong ?

You are using / as separator in your ToString format. But your current culture seems to has - as date separator. That is why you see the difference. You can pass CultureInfo.InvariantCulture with ToString.
Like:
DateTimeObject.ToString("MM/dd/yyy HHmmss", CultureInfo.InvariantCulture)

DateTime.ToString replaces / with the current date separator and : with the current time separator. You're passing in the format yourself, and it does not match what's in the Region settings.
To use the Region settings, use ToShortDateString() and ToShortTimeString().

You can use this:
DateTime.now.ToString("yyyyMMddHHmmss");
or
DateTime.now.ToString("mm-dd-yyyy");

Is a DateTime.ToString format expression affected by the current culture locale?

I have some code that is logging a timestamp in format from a thick client app
DateTime.UtcNow.ToString("MM/dd/yy HH:mm:ss")
Now, on a client running in China (not sure exactly which locale) this is producing a date in the log with the format
11-20-13 02:14:03
I notice it's using - instead of / to delimit the parts, even though I explicitly wanted /
I tried to set the current culture to Chinese simplified zh-CN but I wasn't able to reproduce how the remote client was able to produce that string
Does current culture locale affect the output of this format string? Or does / have some other meaning I'm not aware of?

Yes, the / character is a placeholder for whatever the current culture uses to separate parts of the date. From MSDN:
The "/" custom format specifier represents the date separator, which is used to differentiate years, months, and days. The appropriate localized date separator is retrieved from the DateTimeFormatInfo.DateSeparator property of the current or specified culture.
As with other format specifiers, you can escape the / with a \:
DateTime.UtcNow.ToString(#"MM\/dd\/yy HH\:mm\:ss")
Or specify an explicit culture when formatting the string:
DateTime.UtcNow.ToString("MM/dd/yy HH:mm:ss", CultureInfo.InvariantCulture)

Yes, that's how it works. / is being replaced with the local date separator. The same applies to : as a time separator. You can find more on MSDN: Custom Date and Time Format Strings.
To change that, escape them with \:
DateTime.UtcNow.ToString(#"MM\/dd\/yy HH\:mm\:ss")

String Parsing a Time

I need to obtain a time in the format of "07:30 am" (not case-sensitive). I'm reading a file which has this in the format "07:30am". Eventually I will be constructing a DateTime from this, so I just need to get this back with a space before the am/pm part.
I can detect the occurrence of the a or p using this:
if(startString.IndexOfAny("ap".ToCharArray()) != -1)
{
}
What's the best ways to do this? I'm guessing I will end up with two strings that can be concatenated with a space? Can Split be used with the above snippet to achieve this?
UPDATE:
I need to end up with a space in the DateTime between the minutes and the AM/PM and I do not want to use regular expressions. So far, nothing I've tried here gives me that...
The actual input I have to handle is in this format:
RecDate: "04/30/2012"
RecTime: "05:30am"
I need to create a new DateTime object from these with a space before the am/pm part.

You have two easy choices:
Use RegEx to fix the formatting:
string newTime = Regex.Replace(startString, #"(?<=[01]\d:[0-5]\d)(?=[ap]m)", " ");
Use DateTime.ParseExact to just import the time as-is:
DateTime newValue = DateTime.ParseExact(
startString,
"hh:mmtt",
CultureInfo.InvariantCulture);
I'm partial to the second approach.
You need to use the Invariant Culture because there is no separator defined between the mm and tt in the format.

Why you are not using Regular Expression for this? ( http://msdn.microsoft.com/de-de/library/system.text.regularexpressions.regex(v=vs.80).aspx ) should be an easy thing for a Regex-Wizard (which I'm not)

Parse Datetime string

I'm trying to convert the following string to datetime. I've searched high and low and can't find the exact formats string and I don't want to resort to parsing it manually.
var dateString = "20110828T134108+0100";
All my attempts fail with FormatException.

Have you tried this?
var date = DateTime.ParseExact( dateString
,"yyyyMMdd\THHmmsszzz"
,CultureInfo.InvariantCulture
);
From MSDN:
If format is a custom format pattern that does not include date or
time separators (such as "yyyyMMdd HHmm"), use the invariant culture
for the provider parameter and the widest form of each custom format
specifier. For example, if you want to specify hours in the format
pattern, specify the wider form, "HH", instead of the narrower form,
"H".

The documentation on the format string is here: http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx
That should get you started. :)

try this format: "yyyyMMdd'T'HHmmss"

Have you tried this:
DateTime.ParseExact("20110828T134108+0100", "yyyyMMdd'T'HHmmsszzzz", CultureInfo.InvariantCulture);