C# already does that, it converts LINQ to expression trees that are then converted by providers to their target query language. I’ve used it on one project to pass around the same query expressions to SQL server and Mongo - you pass a type of IQueryable<T> which represents an expression tree.

For instance

var seniors = query(from u in Users where u.Age > 65 && u.Sex == “male” select u)

IEnumerable<Users> query(IQueryable<Users>)