> or< operator on datetime field stored as string in Mongo db using C# driver

Question

I have a collection in Mongo db in which every document has a field date inserted in format "mm/dd/year hrs:min". Now, I am trying to write a query using c# to delete all the records that are 12 months older than the current date.

I am using something like this

deliveryHistory.DeleteMany(x => Convert.ToDateTime(x.DateInserted) < DateTime.Now.AddMonths(-12)); 

which throws the error of to datetime not supported.

Answer 1

you can do it with the following delete command. i'm afraid there is no strongly typed way to do it with the C# driver though. it would be best if you store the dates as ISODate in the db.

await collection.DeleteManyAsync(@"
{
    $expr: {
        $gt: [
            {
                $subtract: [
                    new Date(),
                    {
                        $dateFromString: {
                            dateString: '$DateInserted',
                            format: '%m/%d/%Y %H:%M'
                        }
                    }
                ]
            },
            31540000000
        ]
    }
}");

note: 31540000000 is the number of milliseconds in a year