How to loop through a dataset in powershell?

Question

I am trying a "very" simple task to output values of each rows from a dataset :

$Data = '' for($i=0;$i -le $ds.Tables[1].Rows.Count;$i++)
{
write-host 'value is : '+$i+' '+$ds.Tables[1].Rows[$i][0]
}

OUTPUT :
value is : +0+ +System.Data.DataSet.Tables[1].Rows[0][0]
value is : +1+ +System.Data.DataSet.Tables[1].Rows[1][0]
value is : +2+ +System.Data.DataSet.Tables[1].Rows[2][0]
value is : +3+ +System.Data.DataSet.Tables[1].Rows[3][0]
value is : +4+ +System.Data.DataSet.Tables[1].Rows[4][0]
value is : +5+ +System.Data.DataSet.Tables[1].Rows[5][0]
value is : +6+ +System.Data.DataSet.Tables[1].Rows[6][0]

How do i get the actual value from the column ?!?!

Answer 1

The parser is having trouble concatenating your string. Try this:

write-host 'value is : '$i' '$($ds.Tables[1].Rows[$i][0])

Edit: Using double quotes might also be clearer since you can include the expressions within the quoted string:

write-host "value is : $i $($ds.Tables[1].Rows[$i][0])"

Answer 2

The PowerShell string evalutation is calling ToString() on the DataSet. In order to evaluate any properties (or method calls), you have to force evaluation by enclosing the expression in $()

for($i=0;$i -le $ds.Tables[1].Rows.Count;$i++)
{ 
  write-host "value is : $i $($ds.Tables[1].Rows[$i][0])"
}

Additionally, the foreach keyword allows you to iterate through a collection or array without needing to figure out the length.

Rewritten -

foreach ($Row in $ds.Tables[1].Rows)
{ 
  write-host 'value is : $($Row[0])
}

Answer 3

Here's a practical example (build a dataset from your current location):

$ds = new-object System.Data.DataSet
$ds.Tables.Add("tblTest")
[void]$ds.Tables["tblTest"].Columns.Add("Name",[string])
[void]$ds.Tables["tblTest"].Columns.Add("Path",[string])

dir | foreach {
    $dr = $ds.Tables["tblTest"].NewRow()
    $dr["Name"] = $_.name
    $dr["Path"] = $_.fullname
    $ds.Tables["tblTest"].Rows.Add($dr)

}


$ds.Tables["tblTest"]

$ds.Tables["tblTest"] is an object that you can manipulate just like any other powershell object:

$ds.Tables["tblTest"] | foreach {
    write-host 'Name value is : $_.name
    write-host 'Path value is : $_.path
}

HTH