Find the min element of Hashtable (Values are - DateTime) on PowerShell - powershell

Question

There is a hashtable of view:
key(string) - value (dateTime)
Have to find the min value among Values (dateTime-s).
Can't find generic method to find such a value. The only way is smth like
$first_file_date = $dates_hash.Values | Measure-Object -Minimum -Maximum
Get-Date ($first_file_date);
Though visibly I get the result ($first_file_date) the actual value casts to GenericObjectMeasureInfo type and I can't cast it back to DateTime to work further.
Any ideas?

Answer 1

The value you're interested in is stored in the Minimum and Maximum properties of the object returned by Measure-Object:
$measurement = $dates_hash.Values | Measure-Object -Minimum -Maximum
# Minimum/oldest datetime value is stored here
$measurement.Minimum
# Maximum/newest datetime value is stored here
$measurement.Maximum
Use ForEach-Object or Select-Object if you want the raw value in a single pipeline:
$oldest = $dates_hash.Values | Measure-Object -Minimum | ForEach-Object -MemberName Minimum
# or
$oldest = $dates_hash.Values | Measure-Object -Minimum | Select-Object -ExpandProperty Minimum

Answer 2

To complement Mathias R. Jessen's helpful answer with an alternative solution based on LINQ:
# Sample hashtable.
$hash = #{
foo = (Get-Date)
bar = (Get-Date).AddDays(-1)
}
# Note that the minimum is sought among the hash's *values* ([datetime] instances)
# The [datetime[] cast is required to find the appropriate generic overload.
[Linq.Enumerable]::Min([datetime[]] $hash.Values)
Use of LINQ from PowerShell is generally cumbersome, unfortunately (see this answer). GitHub proposal #2226 proposes improvements.

Answer 3

Just use Sort-Object for this:
$dates_hash = #{
"a" = (Get-Date).AddMinutes(4)
"b" = (Get-Date).AddMinutes(5)
"c" = (Get-Date).AddMinutes(2)
"d" = (Get-Date).AddMinutes(5)
"e" = (Get-Date).AddMinutes(1)
"f" = (Get-Date).AddMinutes(6)
"g" = (Get-Date).AddMinutes(8)
}
$first_file_date = $dates_hash.Values | Sort-Object | Select-Object -First 1
Or if you want the whole object:
$first_file = $dates_hash.GetEnumerator() | Sort-Object -Property "Value" | Select-Object -First 1