How to concatenate array of integers into comma separated string

Question

I have two question, acually:

1. How to join array of integers into comma separated string? (1,2,3) => \"1,2,3\"
2. How to convert array of integers t

Answer 1

Next code snippet could help out on understanding:

$arraylist = New-Object 'system.collections.arraylist'
$arraylist.Add(111)           | Out-Null
$arraylist.Add([string]222)   | Out-Null
$arraylist.Add('"' + 3 + '"') | Out-Null
for($i=0; $i -lt $arraylist.Count; $i++ ){
    write-host $i, $arraylist[$i], $arraylist[$i].GetType()
}
write-host ''
$csv = $arraylist -join ','
$csv

Output:

0 111 System.Int32
1 222 System.String
2 "3" System.String

111,222,"3"

Additional view of (un)importance of " double quotes in a string type shows next + operation (sum of integers but concatenation of strings):

    write-host $i, $arraylist[$i], $arraylist[$i].GetType().Name, ($arraylist[$i] + 55) 

gives next output:

0 111 Int32 166
1 222 String 22255
2 "3" String "3"55

111,222,"3"

However, " double quotes have another important and meaningful role in .csv file when imported e.g. to Excel sheet.