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WriteObject enumerateCollection set to true not enumerating DataRowCollection in System.Data.DataTable #6453
Description
Steps to reproduce
Create a simple cmdlet with this method as the ProcessRecord()
protected override void ProcessRecord()
{
DataTable dt = new DataTable("test");
dt.Columns.Add("Name", typeof(string));
dt.Columns.Add("Age", typeof(string));
DataRow dr = dt.NewRow(); dr["Name"] = "John"; dr["Age"] = "20";
DataRow dr2 = dt.NewRow(); dr["Name"] = "Susan"; dr["Age"] = "25";
dt.Rows.Add(dr); dt.Rows.Add(dr2);
WriteObject(dt, enumerateCollection: true);
}Expected behavior
Return type should be a System.Array with the 2 rows enumerated.
(This works on Powershell 5 with the full .NET Framework)
Actual behavior
Return type is a DataTable not a System.Array with the rows enumerated.
Environment data
> $PSVersionTable
Activity
mklement0 commentedon Mar 21, 2018
At least at first glance the current behavior makes more sense, given that
[System.Data.DataTable]does not implement the[System.Collections.IEnumerable]interface and PowerShell therefore doesn't consider it a collection.That the behavior changed is definitely disconcerting, however, and I hope someone else can shed light on this.
Using
WriteObject(dt.Rows, enumerateCollection: true)instead fixes the problem (because the type of.Rowsis[System.Data.DataRowCollection], which does implement[IEnumerable])BrucePay commentedon Mar 21, 2018
The issue is here in the code:
PowerShell/src/System.Management.Automation/engine/LanguagePrimitives.cs
Line 479 in 41b3161
Enumerating DataTables is explicitly disabled .
I don't know why this was done or if there is any reason not to turn it back on (other than it's a breaking change from 6.0). I've marked it for review by the committee.
daxian-dbw commentedon Mar 21, 2018
I think the code was if/def'ed out originally when
DataTableis not available in .NET Core.SteveL-MSFT commentedon Mar 28, 2018
@PowerShell/powershell-committee reviewed this and it makes sense to have it consistent in that datarows are enumerated
Matteo-T commentedon Oct 31, 2022
FWIW, there is a typo in Abhi (@abhisheksinha89)'s repro:
which would make it look like this was not fixed :-)