Not able to Insert DateTime Values in DateTime Declared Empty Array!!!

PowerShell Help
1

$TS3=1
If ($BCODE -LIKE “16”)
{
$TS1= [datetime]::ParseExact($tcode,“yyyyMMddhhmmss”, $null)

[datetime]$a = @()

$i=0
do
{
$a[$i]+= ,$TS1
Write-host $a[$i]
$i++
}
While($i -le $TS3)
$TS3++
}
Else
{
}

$tcode contains the string value in yyyyMMddhhmmss format. So, I am converting that value in to datetime and then would store all the values in an array and then would sort the array to get the latest timestamp.

I am trying to save every DateTime value that is coming through $TS1 in an Array every time the loop runs. Its giving the error below:

Cannot convert the “System.Object” value of type “System.Object” to type “System.DateTime”.
At C:\Users\c0srivastavad\Desktop\Untitled2.ps1:47 char:2

  • $a[$i]+= ,$TS1

Please let me know where I am making the mistake. I am learning Powershell along the way so dont have much knowledge.

Thanks
Devesh

2

The error is because you have a comma just in front of the $TS1 in the line where you’re trying to add the value to your array. since you’ve put a comma in front, powershell sees this as a collection rather than a single datetime object. Also, you should choose to specify array indexes by iterating through values of $i, OR use the += operator when adding values to an array, otherwise you could end up combining specific values. Simple example of the differences:

$a = @()
For($b in $(1..5)){
$a+=$b
}
$a
$a.getType()
$a[0].getType()

OR

$a=1..5
$a
For($i=0;$i -lt $a.count;$i++){
$a[$i]=$i+5
}
$a
$a.getType()
$a[0].getType()

What you’re trying to achieve can be done like this (assuming you have an array of strings matching your specific datetime format):

$array=@()
ForEach($itm in $TS1){
$array+=[datetime]::ParseExact($itm,"yyyyMMddhhmmss",$Null)
}
$array
$array | Sort-Object
3

Adding to an array is a quite expensive operation as PowerShell arrays are read-only, which means it has to recreate an array with a new object on every operation. It’s simpler to just catch the output.

$array = ForEach($itm in $TS1){
    [datetime]::ParseExact($itm,"yyyyMMddhhmmss",$Null)
}

Try it yourself.

Measure-Command {
    $array = @()

    foreach($i in 1..10000) {
        $array += $i
    }
} | Select-Object TotalMilliseconds

Measure-Command { 
    $array = foreach($i in 1..10000) {
        $i
    }
} | Select-Object TotalMilliseconds


TotalMilliseconds
-----------------
        4225.8069
          30.3903