Question

I am trying to find a more efficient way to add additional information to a list from a query. For example, if I have a list of objects with the ObjectID and StringA set, I would like to query the database based on ObjectID to retrieve StringB and StringC:

public class SomeObject {
    public int ObjectID { get; set; }
    public string StringA { get; set; }
    public string StringB { get; set; }
    public string StringC { get; set; }
}

public void AddInformationToSomeObjects(List<SomeObject> someObjects)
{
    var listOfIDs = someObjects.Select(so => so.ObjectID).ToList();
    var informationToAdd = db.Table.Where(t => listOfIDs.Contains(t.ObjectID)).Select(t => new { ObjectID = t.ObjectID, StringB = t.StringB, StringC = t.StringC }).ToList();

    foreach (var someObject in someObjects)
    {
        var information = informationToAdd.Where(i => i.ObjectID == someObject.ObjectID).FirstOrDefault();
        someObject.StringB = information.StringB;
        someObject.StringC = information.StringC;
    }
}

Is there any way to combine the query and the assignment into one statement?

Answer 1

Just update the whole List…

public void AddInformationToSomeObjects(IEnumerable<SomeObject> someObjects)
{
    someObjects =
        from obj in someObjects
        join dbObj in db.Table
        on obj.ObjectID equals dbObj.ObjectID
        select new SomeObject
        {
            ObjectID = obj.ObjectID,
            StringA = obj.StringA,
            StringB = dbObj.StringB,
            StringC = dbObj.StringC
        }
}