Remove matched Rows from two Datatable
Assuming that you load the data into your DataTable instances from database, it's better to issue a direct DELETE FROM ... query over database rather than iterate on a client.

As a side note - it is an awful practice to compare dates by comparing strings. If your table has a DateTime column it's much better to cast the value to DateTime and compare typed dates like that:

DateTime dateFromRange = ((DateTime)rw[0]).Date;
....

    DateTime getDate = ((DateTime)row[0]).Date;
    if (dateFromRange == getDate)
....