Search Problem

Here I search Manufacturer

My problem is Manufacturer is Tatavista. But in my database Tatavista and tatvista both are present.

if i search with tatavista i get both results.

 if search with tatavista i need to get tatavista only.

This is my code:

viewModel = CarDb.cars.Where(g => g.Manufacturer == Manufacturer || string.IsNullOrEmpty(Manufacturer.Trim().tolower().toupper()))