C# linq finding all string values in a list there match in mongodb

Question

My question might not be specific for MongoDb , even though I am using it.

I want to find all records that are contained in my List

Previously I could search with finding OrderNumber Collection.Find an incoming parameter of a string orderNumber

Thus a method collection.find looked like this:

IEnumerable<Activity> activity = Collection.Find<Activity>(o => o.OrderNumber == orderNumber).ToList();

However, now i want to find List

So do I NEED to modify this statement to be a LOOP to find, or can this be modified to Find all the records in the List ?

public static IEnumerable<Activity> GetActivitiesByOrderNumber(List<OrderStuff> orderNumber)
{

     IEnumerable<Activity> activity = Collection.Find<Activity>(o => o.OrderNumber == orderNumber).ToList();
     return activity;
}

Update

Error CS1503 Argument 1: cannot convert from 'JobManager.Models.Activity' to 'JobManager.Controllers.APIs.OrderStuff'

public static IEnumerable<Activity> GetActivitiesByOrderNumber(List<OrderStuff> orderNumber)
{
    IEnumerable<Activity> activity = Collection.Find<Activity>(o => orderNumber.Contains(o)).ToList();
    return activity;
}

Activity class

public class Activity
{

    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }
    public DateTime? CreatedDate { get; set; }
    public int CreatedById { get; set; }
    public string CreatedByName { get; set; }

    // ..... etc..
 }

OrderStuff class

public class OrderStuff
{
    public string id { get; set; }
}

Answer 1

Try this:

public static IEnumerable<Activity> GetActivitiesByOrderNumber(List<Activity> activities)
{
     IEnumerable<Activity> activity = Collection.Find<Activity>(o => activities.Contain(o)).ToList();
     return activity;
}

Answer 2

Check out the following working version, I have taken some liberty to change the object names for correct representation of collection.

public static IEnumerable<Activity> GetActivitiesByOrderNumber(List<OrderStuff> orderNumbers)
{
   List<string> OrderStuffIds = orderNumbers.Select(o => o.Id);

    IEnumerable<Activity> activities = Collection.Where(a => OrderStuffIds.Contains(a.Id)).ToList();
    return activity;
}

Explanation:

Why the original code did not work ?

You are comparing the OrderStuff with Activity , when there's no apparent relation between the two, mostly you need to compare using the Id field

Modifications required

• Fetch the Id list from the OrderStuff List
• Use the same for comparison, when fetching the Activity list, by comparing Ids

Further Issues:

• Even the current solution is a O(N^2) implementation
• Can be further improved by transforming List<OrderStuff> to Hashset<OrderStuff> , which will do a binary search in O(LogN) time instead of O(N)

• Something like:

   HashSet<OrderStuff> orderNumberHashSet = new HashSet<OrderStuff>(orderNumbers);