Filter table with doule value

Feel free on trying the following LINQ as an alternate

Assign Activity
dt2 =

(From d in dt1.AsEnumerable
let c1 = d("Descr.......").toString.Trim.ToUpper
Let c2 = d("Novo saldo....").toString.Trim
Where c1.Contains("CAR_DUPL") AND CDbl(c2) >= 500
Select r=d).CopyToDataTable

just complete the column name
ensure that the data is within the expected formats and values

Handling empty results: