datatable bulk update

i have a datatable with a column called payment.  I need to change all rows to be the value of Payment * -1.  How do I go about this?
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Imran Javed ZiaConsultant Software Engineer - .NET ArchitectCommented:
Dim dt As DataTable
        For i As Integer = 0 To dt.Rows.Count
            dt.Rows(i)("Payment ") *= -1

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Imran Javed ZiaConsultant Software Engineer - .NET ArchitectCommented:
for c#

for (int i = 0; i < dt.Rows.Count; i++)
                dt.Rows[i]["Payment"] = Convert.ToDouble(dt.Rows[i]["Payment"]) * -1;
                dt.Rows[i]["Payment"] = Convert.ToInt32(dt.Rows[i]["Payment"]) * -1;

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Fraser_AdminAuthor Commented:
i'm getting crazy floating point numbers with this?
like if i'm expecting 181.35 i'm getting 181.35000000001

i try math.round but it doesn't seem to work.
Imran Javed ZiaConsultant Software Engineer - .NET ArchitectCommented:
in db sp/query use percision as following

select cast(colName as numeric(18,2) colName from tbl

you can change percisoon as per requiremnt 18,2 or else 2 means 2 decimal points
Fraser_AdminAuthor Commented:
disregard that last comment.  that works great.
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