Unable to determine the serialization information when trying to query the child MongoDB C#

Um sharing my code Im using to query and get a matching child element to do an update to an element in an array in mongoDB Collection

                var filter = Builders<Fruit>.Filter.Eq( x => x.Id, fruitId );
                var update = Builders<Fruit>.Update.Set( x => x.FruitDetails.FirstOrDefault( y => y.Id.Equals( FruitDetail.Id ) ), FruitDetail );

Unfortunately this throws an error in Update Linq Query and i do not know how to fix this

   Unable to determine the serialization information for the expression: (Fruit x) => Enumerable.FirstOrDefault<FruitDetails>(x.FruitDetails, (Fruit p) => p.Id.Equals(<mongoID>)).

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Link to original article：https://stackoverflow.com/questions/33564104/unable-to-determine-the-serialization-information-when-trying-to-query-the-child