It's not possible to cancel executing query. The problem relates to both MongoQueryable and MongoCollection methods. Based on assumption that 3rd party tools can "kill" connection and corresponding query, it would be nice to have methods like Close on MongoCursor, for example.

The use case is the following:
Incoming HTTP request is processed and query is executed. But, for example, query takes long time and user closes or refreshes browser. But unfortunately the query still executes and consumes resources. There is no way to reach underlying connection, on which query executes, and close it.