Compare dates with different formats in csv file - powershell

Question

Whats a good way to compare dates in a csv file that looks like this:
Date1,Date2,Date3
11/10/2016 9:45:00 PM,20161110,11/10/2016
11/15/2016 11:24:00 PM,20160924,11/10/2016
If a match is found, append a column like so...
Date1,Date2,Date3,MatchDates
11/10/2016 9:45:00 PM,20161110,11/10/2016,Match Found
11/15/2016 11:24:00 PM,20160924,11/10/2016,No Match Found
updated
Trying the code that is in the comments:
When comparing this with 2 of the columns...
$csvFile = 'C:\Scripts\Tests\test1.csv'
Import-Csv $csvFile | Select-Object *, #{n='MatchDates';e={
if(([datetime]$_.Date1).Date -eq $_.Date3){
'Match Found'
}Else{
'No Match Found'
}}} |
Export-Csv "$csvFile-results.csv" -NoTypeInformation -Force
output (isCorrect)...
Date1,Date2,Date3,MatchDates
11/10/2016 9:45:00 PM,20161110,11/10/2016,Match Found
11/15/2016 11:24:00 PM,20160924,11/10/2016,No Match Found
However, if I try to compare all 3 columns using the following code
Import-Csv $csvFile | Select-Object *, #{n='MatchDates';e={
if((([datetime]$_.Date1).Date -eq $_.Date3) -and (([datetime]$_.Date2).Date -eq $_.Date3) -and (([datetime]$_.Date1).Date -eq $_.Date2)){
'Match Found'
}Else{
'No Match Found'
}}} |
Export-Csv "$csvFile-results.csv" -NoTypeInformation -Force
output (isNotCorrect)...
Date1,Date2,Date3,MatchDates
11/10/2016 9:45:00 PM,20161110,11/10/2016,
11/15/2016 11:24:00 PM,20160924,11/10/2016,No Match Found
As you can see the value of row 1 and the last column is $null instead of showing Match Found
Maybe I'm not understanding something correctly?

Answer 1

You were on the right track with what we discussed in comments. Problem was with that middle date. It does not convert to a [datetime] without some help. That is where ParseExact comes in handy. Consider the following:
PS D:\temp> [datetime]"20160924"
Cannot convert value "20160924" to type "System.DateTime". Error: "String was not recognized as a valid DateTime."
At line:1 char:1
+ [datetime]"20160924"
+ ~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvalidCastParseTargetInvocationWithFormatProvider
PS D:\temp> [datetime]::parseexact("20160924","yyyyMMdd",[System.Globalization.CultureInfo]::CurrentCulture)
Saturday, September 24, 2016 12:00:00 AM
Note the second example returned a proper date object.
Do you remember the transitive property from math? We use that for simple comparison to see if all dates are the same. Not the only way by far but a simple one nonetheless. Building off your calculated property code
$csv | Select-Object *,#{Name='MatchDates';Expression={
$date1 = ([datetime]$_.Date1).Date
$date2 = ([datetime]::parseexact($_.Date2,"yyyyMMdd",[System.Globalization.CultureInfo]::CurrentCulture)).Date
$date3 = ([datetime]$_.Date1).Date
if($date1 -eq $date2 -and $date2 -eq $date3){
'Match Found'
} else {
'No Match Found'
}
}
}
Cleared up the if logic by saving the casted values in temproary variables.