CODEWITHSUNDEEP
c#entity-framework
mj.e
mj.e

Reputation: 43

Find a record in dbset without a primary key

I have a Student table wherein I find a record with primary key UserID using Find

        var currentUserId = User.Identity.GetUserId();
        var newid = db.Students.FirstOrDefault(d => d.UserID == currentUserId);

        if (newid == null)
        {
            newid = db.Students.Create();
            newid.UserID = currentUserId;
            db.Students.Add(newid);

        }

        Student student = db.Students.Find(newid.UserID);
        if (student == null)
        {
            return HttpNotFound();
        }

My question is how do I find a record but cannot use his primary key? In my case my IndividualInventoryRecord has primary key RecordID. I want to find a record from this table using FK UserID

I have tried this but inventory returns null

var userInv = db.IndividualInventoryRecords.FirstOrDefault(d => d.UserID == currentUserId);

        if (userInv == null)
        {
            userInv = db.IndividualInventoryRecords.Create();
            userInv.UserID = currentUserId;
            db.IndividualInventoryRecords.Add(userInv);
        }

        IndividualInventoryRecord inventory = db.IndividualInventoryRecords.FirstOrDefault(user => user.UserID == currentUserId);

        if (inventory == null)
        {
            return HttpNotFound();
        }

I also tried using SingleOrDefault()

Upvotes: 1

Views: 834

Answers (2)

Ivan Stoev
Ivan Stoev

Reputation: 205939

Unfortunately Find method is the only method which takes the local cache into account. All standard Queryable methods are translated to SQL and executed in database, hence return only existing database table records.

However it's not that hard to write your own custom extension method similar to Find but with predicate expression:

public static partial class DbSetExtensions
{
    public static T FindFirst<T>(this DbSet<T> source, Expression<Func<T, bool>> predicate)
        where T : class
    {
        return source.Local.AsQueryable().FirstOrDefault(predicate) ?? source.FirstOrDefault(predicate);
    }
}

and use it instead of FirstOrDefault:

var inventory = db.IndividualInventoryRecords.FindFirst(e => e.UserID == currentUserId);

Upvotes: 2

Emre Kabaoglu
Emre Kabaoglu

Reputation: 13146

Because, you are not saving to database the userInv instance. Just save it;

    if (userInv == null)
    {
        userInv = db.IndividualInventoryRecords.Create();
        userInv.UserID = currentUserId;
        db.IndividualInventoryRecords.Add(userInv);
        db.SaveChanges();
    }
    IndividualInventoryRecord inventory = db.IndividualInventoryRecords.FirstOrDefault(user => user.UserID == currentUserId);

Upvotes: 1

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