MongoDb $projection query on C# - mongodb

Question

I need help on how to build a MongoDB query from the C# Driver. What I'm trying to make is a datediff in milliseconds and then filter those results where the datediff in milliseconds is greater or equal than an specific number.
The mongodb query that I use in the mongo shell is:
db.getCollection('Coll').aggregate(
[
{$project : {
"dateInMillis" : {$subtract: [ new Date(), "$UpdateDate" ]},
"Param2": "$Param2",
"Param3": "$Param3"}
},
{$match :{ dateInMillis : { $gte : 2662790910}}}
],
{
allowDiskUse : true
});
Which would be the equivalente C# expression?
I've been trying to make the query in many different ways without any result.

Answer 1

I finally found the way to make the aggregate query through the mongodb c# driver. I don't know if its the most efficient way but it's working.
var project = new BsonDocument()
{
{
"$project",
new BsonDocument
{
{"dateInMillis", new BsonDocument
{
{
"$subtract", new BsonArray() {new BsonDateTime(DateTime.UtcNow), "$UpdateDate" }
}
}
},
{
"Param2", "$Param2"
},
{
"Param3", "$Param3"
},
{
"_id", 0
}
}
}
};
var match = new BsonDocument()
{
{
"$match",
new BsonDocument
{
{
"dateInMillis",
new BsonDocument {
{
"$gte",
intervalInMilliseconds
}
}
}
}
}
};
var collection = db.GetCollection<CollClass>("Coll");
var pipeline = new[] { project, match };
var resultPipe = collection.Aggregate<CollClassRS>(pipeline);