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  1. C# Driver
  2. CSHARP-3737

Use $expr when AggregateOptions.Let is specified

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    • Type: Icon: New Feature New Feature
    • Resolution: Unresolved
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: None
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      The following query returns no results because it is querying for the literal value $$surname, not the value of the variable specified in AggregateOptions.Let:

      var query = coll.Aggregate(new AggregateOptions {Let = new BsonDocument{{ "surname", "Smith"}}})
                .Match(x => x.LastName == "$$surname");

      In order to query for the value of the $$surname variable you must use $expr. So the correct query is:

      var query = coll.Aggregate(new AggregateOptions {Let = new BsonDocument{{ "surname", "Smith"}}})
                .AppendStage<Person>(
                    new BsonDocument {{ "$match",
                        new BsonDocument {{
                            "$expr", new BsonDocument {{ "$eq", new BsonArray {"$LastName", "$$surname"} }}
                        }}
                    }});

      If AggregateOptions.Let is provided, the driver should render expressions using the variable with $expr. For example, the Match in the first example should render something akin to the second example automatically.

            Assignee:
            Unassigned Unassigned
            Reporter:
            james.kovacs@mongodb.com James Kovacs
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              Created:
              Updated: