Get objects whose property does not exist in enumerable

Question

Multiple answers have led me to the following 2 solutions, but both of them do not seem to be working correctly.

What I have are 2 objects

public class DatabaseAssignment : AuditableEntity
{
    public Guid Id { get; set; }
    public string User_Id { get; set; }
    public Guid Database_Id { get; set; }       
}

public class Database : AuditableEntity
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string Server { get; set; }
    public bool IsActive { get; set; }
    public Guid DatabaseClientId { get; set; }
}

Now, the front-end will return all selected Database objects (as IEnumerable) for a given user. I am grabbing all current DatabaseAssignments from the database for the given user and comparing them to the databases by the Database.ID property. My goal is to find the DatabaseAssignments that I can remove from the database. However, my solutions keep returning all DatabaseAssignments to be removed.

if (databases != null)
{
    var unitOfWork = new UnitOfWork(_context);
    var userDatabaseAssignments = unitOfWork.DatabaseAssignments.GetAll().Where(d => d.User_Id == user.Id);

    //var assignmentsToRemove = userDatabaseAssignments.Where(ud => databases.Any(d => d.Id != ud.Database_Id));
    var assignmentsToRemove = userDatabaseAssignments.Select(ud => userDatabaseAssignments.FirstOrDefault()).Where(d1 => databases.All(d2 => d2.Id != d1.Database_Id));
    var assignmentsToAdd = databases.Select(d => new DatabaseAssignment { User_Id = user.Id, Database_Id = d.Id }).Where(ar => assignmentsToRemove.All(a => a.Database_Id != ar.Database_Id));

    if (assignmentsToRemove.Any())
    {   
       unitOfWork.DatabaseAssignments.RemoveRange(assignmentsToRemove);
    }
    if (assignmentsToAdd.Any())
    {
       unitOfWork.DatabaseAssignments.AddRange(assignmentsToAdd);
    }
    unitOfWork.SaveChanges();
}

sharmav1 · Accepted Answer · 2018-06-22 17:55:28Z

1

I think u are looking for an Except extension, have a look at this link

LINQ: Select where object does not contain items from list

Or other way is with contains see below Fiddler link :

https://dotnetfiddle.net/lKyI2F

edited Jun 22, 2018 at 17:55

answered Jun 22, 2018 at 14:02

sharmav1

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4 Comments

Irrelevant_Coder Over a year ago

I followed the answer on this SO and still have the same problem. var databaseIds = databases.Select(d => d.Id).ToList(); var assignmentsToRemove = userDatabaseAssignments.Where(ud => !databaseIds.Contains(ud.Database_Id)); AssignmentsToRemove still contains objects with matching Database_Id's.

sharmav1 Over a year ago

What list is databaseids? Is it the collection of ids you want or the ones you don't want? Try select ids which you don't want into a list then replace above with: userDatabaseAssigbments.Where(lst => !idsDontwant.Contains(lst.Id)).ToList(); I'm not on my laptop so can't test anything.

Irrelevant_Coder Over a year ago

databaseids is the list of database ids I want since I'm returning the selected items from the front end. So, I need to get the databaseassignments that do not contain the id's in that list in order to remove them.

sharmav1 Over a year ago

I have updated my answer and added a fiddle link for you, please check

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