Filtering rows in a datatable

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Hello all,

I am trying to filter rows in a datatable by the given criteria:

(1)The rows should be seen in datatable if the column has a value other than white.
(2)The former and latter 2 rows must be added as well if the rule 1 is met.

For ex;

Input
LineNumber Desc Color
0001--------aas---White
0002-------brrf---White
0003--------vea---White
0004------adwec---White
0005------45fca---Green
0006-----fvsdca---White
0007-----rtvsca---White
0008-----4dsdea---White

Output
LineNumber Desc Color
0003--------vea---White
0004------adwec---White
0005------45fca---Green
0006-----fvsdca---White
0007-----rtvsca---White

What I have tried so far?

C#

var result = from r in dtOld.AsEnumerable()
             where r.Field<string>("Color") != "White"
             select r.Field<string>("Line#");

List<int> lstIntOld = new List<int>();
foreach (var item in result)
{
    int numberAdd = Convert.ToInt32(item.ToString().TrimStart('0'));
    lstIntOld.Add(numberAdd - 2);
    lstIntOld.Add(numberAdd - 1);
    lstIntOld.Add(numberAdd);
    lstIntOld.Add(numberAdd + 1);
    lstIntOld.Add(numberAdd + 2);
}

lstIntOld = lstIntOld.Distinct().Where(ix => ix >= 0).ToList();

I found the line numbers which I should add and put them to a list. Now I will filter the datatable by matching those numbers from that list. But is there a cleaner or better way to accomplish this?

Thanks in advance

Posted 18-Mar-15 6:26am

wonder-FOOL

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manchanx · Answer 1 · 2015-03-18T06:49:00

My compliment for your presentation of your question!

This is how I would do it - or at least my ~~first~~ second iteration *. Note there's no "dtNew" - I just remove the unwanted rows from "dtOld". If you want to keep "dtOld" around you would have to copy the rows.

C#

int inclusionSpan = 2;
bool[] keepRow = new bool[dtOld.Rows.Count + inclusionSpan * 2];
int colorColumnIndex = dtOld.Columns.IndexOf("Color");

for (int rowIndex = 0; rowIndex < dtOld.Rows.Count; rowIndex++)
{
    if (dtOld.Rows[rowIndex].Field<string>(colorColumnIndex) != "White")
    {
        for (int includeOffset = 0; includeOffset <= inclusionSpan * 2; includeOffset++)
            keepRow[rowIndex + includeOffset] = true;

        rowIndex += inclusionSpan;
    }
}

for (int rowIndex = dtOld.Rows.Count - 1; rowIndex >= 0 ; rowIndex--)
{
    if (! keepRow[rowIndex + inclusionSpan])
        dtOld.Rows.RemoveAt(rowIndex);
}

* : Tired, maybe there's a flaw somewhere with the inclusionSpan, would have to test it.