CSHARP-4669 noted high memory usage when using FLE with GridFS. A forums user noticed the following:

The EncryptField and EncryptFieldAsync methods both call UnwrapValue, which is:

private BsonValue UnwrapValue(byte[] encryptedWrappedBytes)
{
    var rawDocument = new RawBsonDocument(encryptedWrappedBytes);
    return rawDocument["v"];
}

As RawBsonDocument is IDisposable, it should be surrounded by a using clause:

private BsonValue UnwrapValue(byte[] encryptedWrappedBytes)
{
    using var rawDocument = new RawBsonDocument(encryptedWrappedBytes);
    return rawDocument["v"];
}

We should implement this improvement and verify that it reduces memory usage when using FLE with large documents such as GridFS.