DateTime.TryParse produces different results in different environments

[Petermarcu]

@Doff3n commented on Wed Feb 14 2018

DateTime.TryParse produces different results in different environments

General

I am trying to parse a date, with DateTime.TryParse and with a provided Norwegian culture and no DatetimeStyles:

var result: DateTime.TryParse("29.01", new CultureInfo("nb-NO", false), DateTimeStyles.None, out var parsedDateTime)

I am purposely sending in "29.01" and expecting the result to parse to a default Datetime: "29.01.2018",
I also expect that 29.01.18 and 29.01.2018 parses to the correct dates.

In norway the date format is dd.MM.YYYY HH:mm
Code:
https://github.com/Doff3n/HelloDate

Commands:

• dotnet build
• dotnet run

Running this on my PC:

• dotnet run
  parsedDateTime: 29.01.2018 00:00:00
  result: True

Running this on the VM:

• dotnet run
  parsedDateTime: 01.01.0001 00.00.00
  result: False

.Net core sdk version: 2.1.4, runtime: 2.0.5

In desperation I have also tried setting Date and Time formats in Windows, but I would have expected the property UseUserOverride: false to not allow user settings.

[danmoseley]

@Doff3n what are the configurations of your host and VM? Both the same Windows version?

[Doff3n]

Localhost/my PC:
OS Name Microsoft Windows 10 Enterprise
Version 10.0.16299 Build 16299
System Type x64-based PC
IISExpress

VM:
OS Name Microsoft Windows Server 2016 Standard
Version 10.0.14393 Build 14393
System Type x64-based PC
IIS 10.0.14393.0

[Doff3n]

I am not sure what configurations to set here.
As I am using useUserOverride = false I expect that the culture is set equally on both machines even with user configurations. But it is hard to find out what this override really does.

[tarekgh]

@Doff3n on your VM, are you sure TryParse returned true?

would be nice too if you can get the output of the following lines on the 2 machines

            foreach (string s in new CultureInfo("nb-NO", false).DateTimeFormat.GetAllDateTimePatterns())
            {
                Console.WriteLine(s);
            }

[Doff3n]

I wrote a console app and built it on the VM, this produces the following different results

Localhost output	VM output
dd.MM.yyyy	dd.MM.yyyy
d. MMM yyyy	d. MMM yyyy
dddd d. MMMM yyyy	dddd d. MMMM yyyy
d. MMMM yyyy	d. MMMM yyyy
dddd d. MMMM yyyy HH:mm
dddd d. MMMM yyyy HH.mm	dddd d. MMMM yyyy HH.mm
d. MMMM yyyy HH:mm
d. MMMM yyyy HH.mm	d. MMMM yyyy HH.mm
dddd d. MMMM yyyy HH:mm:ss
dddd d. MMMM yyyy HH.mm.ss	dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH:mm:ss
d. MMMM yyyy HH.mm.ss	d. MMMM yyyy HH.mm.ss
dd.MM.yyyy HH:mm
dd.MM.yyyy HH.mm	dd.MM.yyyy HH.mm
d. MMM yyyy HH:mm
d. MMM yyyy HH.mm	d. MMM yyyy HH.mm
dd.MM.yyyy HH:mm:ss
dd.MM.yyyy HH.mm.ss	dd.MM.yyyy HH.mm.ss
d. MMM yyyy HH:mm:ss
d. MMM yyyy HH.mm.ss	d. MMM yyyy HH.mm.ss
d. MMMM	d. MMMM
d. MMMM	d. MMMM
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK	yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK	yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'	ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'	ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
yyyy'-'MM'-'dd'T'HH':'mm':'ss	yyyy'-'MM'-'dd'T'HH':'mm':'ss
HH:mm
HH.mm	HH.mm
HH:mm:ss
HH.mm.ss	HH.mm.ss
yyyy'-'MM'-'dd HH':'mm':'ss'Z'	yyyy'-'MM'-'dd HH':'mm':'ss'Z'
dddd d. MMMM yyyy HH:mm:ss
dddd d. MMMM yyyy HH.mm.ss	dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH:mm:ss
d. MMMM yyyy HH.mm.ss	d. MMMM yyyy HH.mm.ss
MMMM yyyy	MMMM yyyy
MMMM yyyy	MMMM yyyy

Copied output localhost:
dd.MM.yyyy
d. MMM yyyy
dddd d. MMMM yyyy
d. MMMM yyyy
dddd d. MMMM yyyy HH:mm
dddd d. MMMM yyyy HH.mm
d. MMMM yyyy HH:mm
d. MMMM yyyy HH.mm
dddd d. MMMM yyyy HH:mm:ss
dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH:mm:ss
d. MMMM yyyy HH.mm.ss
dd.MM.yyyy HH:mm
dd.MM.yyyy HH.mm
d. MMM yyyy HH:mm
d. MMM yyyy HH.mm
dd.MM.yyyy HH:mm:ss
dd.MM.yyyy HH.mm.ss
d. MMM yyyy HH:mm:ss
d. MMM yyyy HH.mm.ss
d. MMMM
d. MMMM
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
yyyy'-'MM'-'dd'T'HH':'mm':'ss
HH:mm
HH.mm
HH:mm:ss
HH.mm.ss
yyyy'-'MM'-'dd HH':'mm':'ss'Z'
dddd d. MMMM yyyy HH:mm:ss
dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH:mm:ss
d. MMMM yyyy HH.mm.ss
MMMM yyyy

Copied output VM:
dd.MM.yyyy
d. MMM yyyy
dddd d. MMMM yyyy
d. MMMM yyyy
dddd d. MMMM yyyy HH.mm
d. MMMM yyyy HH.mm
dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH.mm.ss
dd.MM.yyyy HH.mm
d. MMM yyyy HH.mm
dd.MM.yyyy HH.mm.ss
d. MMM yyyy HH.mm.ss
d. MMMM
d. MMMM
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
ddd, dd MMM yyyy HH':'mm':'ss 'GMT'
yyyy'-'MM'-'dd'T'HH':'mm':'ss
HH.mm
HH.mm.ss
yyyy'-'MM'-'dd HH':'mm':'ss'Z'
dddd d. MMMM yyyy HH.mm.ss
d. MMMM yyyy HH.mm.ss
MMMM yyyy
MMMM yyyy

[Doff3n]

.Net core runtime 1.0 is also installed on the VM, but the console app has
<TargetFramework>netcoreapp2.0</TargetFramework>

[tarekgh]

@Doff3n here is what I think happened: on the VM, TryParse failed (returned false and not true). which means the parsing is failed and you cannot depend on the return datetime.

The reason it failed is that on the VM, the default time pattern HH.mm while on the other machine it is HH:mm. so when parsing "29.01", the parser cannot know if to parse it as a date or parse as time because the date and the time separator are same ".".

your code should always use ParseExact to ensure the result. something like

var result: DateTime.TryParseExact("29.01", "dd.MM", new CultureInfo("nb-NO", false), DateTimeStyles.None, out var parsedDateTime)

Please, lat's know if this is not the case.

[Doff3n]

We are implementing a simple string filter, so we were expecting not to know the date format, but support a range of formats

[joperezr]

@tarekgh is this something we need to fix for 2.1?

[Doff3n]

It looks like the VM only has the HH.mm format in Windows, while my PC has HH:mm in addition to HH.mm

[tarekgh]

We are implementing a simple string filter, so we were expecting not to know the date format, but support a range of formats

Expecting DateTime parsing to succeed with any string is the wrong assumption. the guidelines for parsing is either you pass the format pattern used with the date formatting or use invariant culture all the time for formatting and parsing. please try to fix your design according to that or handle the parsing failure when it happens.

It looks like the VM only has the HH.mm format in Windows, while my PC has HH:mm in addition to HH.mm

Globalization data can change between the different OS versions. so this is expected.

in summary, this is by design from the framework side.