PowerShell may unroll collections, that is replace an original collection with an array of its items or just a single item.
This fact is especially easy to forget for some complex objects like
[System.Data.DataTable]. PowerShell may treat it as a collection of
[System.Data.DataRow] and the original table instance may be "lost".
The common workaround is use of the comma operator which wraps an argument with an array of a single item. This array is unrolled and this gets its single item as it is, not unrolled.
Scripts
- Test-1-unrolled-adding.ps1 shows unrolling on adding items to an array using
+=. - Test-2-unrolled-output.ps1 shows a collection unrolled on output from a function.
- Test-3-unrolled-return.ps1 is the similar script which uses
returnexplicitly. - Test-4-unrolled-if.ps1 shows how
if ($x) {$y}unrolls data, see also Missing-ternary-operator.
- Stack Overflow Append an Array to an Array of Arrays
- Stack Overflow Strange behaviour in function returning DataSet/DataTable
- PowerShellTraps/issues/5