MongoDB C＃2.0驱动程序查询，其中字段A小于字段B

Question

I am using the C# 2.0 MongoDB Driver.

I am trying to find all documents where field A is less than field B.

I tried this:

var filter = Builders<Stock>.Filter.Where(s => s.LastPrice < s.MosPrice);
var result = await _collection.Find(filter).ToListAsync();
return result;

But I received the following error:

System.ArgumentException Unsupported filter: (Serialization(LastPrice) < Serialization(MosPrice)).

How can I perform this query using the new C# MongoDB Driver?

Answer 1

To solve this type of queries I use BsonJavaScript :

With old driver :

var filter = Query.Where(new BsonJavaScript("this.LastPrice < this.MosPrice"));

With new driver :

var filter = new BsonDocument(new BsonDocument("$where", new BsonJavaScript("this.LastPrice < this.MosPrice")));

Answer 2

Problem occurs becouse in where condition you try to filter by not constant value. Mongo db driver not support this case.

Answer 3

Seems that you simply cannot:

"The issue with your query is that MongoDB does not allowing comparing two fields to each other. You can only compare fields to a constant. Because of this restriction, we cannot convert the query. It is simply not valid MongoDB syntax.

I'm going to close this ticket as Works as Designed."

https://jira.mongodb.org/browse/CSHARP-1592