Dear Sudhan,
Examine the detailed properties of the element you are trying to retrieve through the filter, e.g., using RevitLookup.
Make sure you know what class of element you are looking for.
From you code, it looks as if you are trying to retrieve a RebarBarType element with a specific style.
They style is presumably accessible via some property or other, maybe hidden away in a parameter value.
Using LINQ, the resulting code might look something like this:
FilteredElementCollector a
= new FilteredElementCollector( doc )
.OfClass( typeof( RebarBarType ) )
.Cast<RebarBarType>()
.Where<RebarBarType>( e
=> element e fulfils your detailed search requirements );
Cheers,
Jeremy