hai provato qualcosa del tipo:
using System;
using System.Collections.Generic;
using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using System.Linq;
using System.Linq.Expressions;
var foundItems = _collection.FindAll(x=> criteria.Any(cc=> xx.StringList.Contains(cc))).ToList();
Dove _collection
è IMongoCollection<TEntity> _collection