Remove rows from a datatable worked very slow

Question

Hi together,

at first i get a big datatable from a oracle database (>100.000 items).
In a second step i want remove items by filtercritera.

But the way i remove the items worked very slow. Perhaps you can help me to find a faster way ;)

Why i do it on this way: There is no way to get performant a smaler datatable direct from oracle.

I hope there is a way to remove items fast from a datatable.


Here the sourcecode:

//Select useable items (works very fast)

var useable = dataTable.Select("(COLUMN1 IN (1,3,7)) AND ISNULL(DATECOLUMN1,'2014-07-22 18:04:35Z') > '2014-07-16 18:04:35Z'");

//List for the Items to delete

var listToDelete = new List<DataSet.TESTDATARow>();

//Check is datarow "useable" (works very slow 120.000 items over 40 sec.)

foreach (var rowItem in dataTable)

{

    var found = useable.Contains(rowItem);

    if (!found)

    {

        listToDelete.Add(rowItem);

    }

}

//Remove items from dataTable (works very fast)

foreach (var logisticDataRow in listToDelete)

{

    dataTable.Rows.Remove(logisticDataRow);

}

i use .Net 4.0
VS 2010

cheers
Guido