Set the top and/or bottom range values for an index order.
public void SetRange( object topRange, object bottomRange );
SetRange sets a range (sometimes called scope) for the active index to limit the number of records visible. For example, setting a topRange of "M" on an index on a character field will make a GotoTop call go to the first key greater than or equal to "M". The bottomRange will make the indicated value the last one visible in the index order. For example, if bottomRange is "Smith" on a lastname index, the last "Smith" on a GotoBottom call will be the current record. Set the top and bottom range to the same value to view only those records with the given range value from the index.
It is not necessary to have both top and bottom ranges set at the same time. Setting either to null will clear an existing top or bottom range. ClearRange will clear both top and bottom range values.
Advantage does not check whether the top and bottom range values are mutually exclusive. When setting ranges on descending indexes, the top range will be set at the logical top of the index (largest key) and the bottom range is at the logical bottom (smallest key).
After calling this method, the reader will be positioned at BOF (beginning of file) so that a call to Read() will then go to the first record.