The MongoDB Driver Quick Tour inserts documents with a counter field,

// generate 100 documents with a counter ranging from 0 - 99 }}var{{ documents = Enumerable.Range(0, 100).Select(i => }}new{{ BsonDocument("counter", i));

but then later tries to query those documents using an i field name:

var filter = Builders<BsonDocument>.Filter.Eq("i", 71);

Either the counter field name should be changed to i, or all the i queries (I count 14) should be changed to counter.