Finding or creating an object in Entity Framework

Question

My domain model and its associations are as follows:

Customer has many Regions
Region has many Locations

Our client supplies us with a CSV file that has the following columns:

Customer name
Region name
Location name
- Latitude
- Longitude
- ...

Based on this information, I have to find or create the customer by name, find or create the region by name, and finally find or update the location by name.

I have tried the following:

var customer = from c in _data.Customer
               where c.Name == cells[0]
               select c;

if (customer == null)
    customer = new Customer(...);

I would follow the same pattern for finding or creating/updating the region and location, however, the problem I run into is that the type of the LINQ query cannot be converted to a Customer-object on line customer = new customers();. I need to reference this customer object later so I can't have two separate variables.

How would I accomplish this in Entity Framework?

nemesv · Accepted Answer · 2012-06-05 05:49:27Z

6

This code

var customer = from c in _data.Customer
               where c.Name == cells[0]
               select c;

Returns all the customers who has the Name equals cells[0] so the return type will be IQueryable<Customer> not a sigle Customer (that's why the customer = new Customer(...) doesn't work).

What you need is to call FirstOrDefault or SingleOrDefault (depending on your requirements.) on it if you want to have back one Customer.

So this should work

var customer = (from c in _data.Customer
               where c.Name == cells[0]
               select c).SingleOrDefault();

answered Jun 5, 2012 at 5:49

nemesv

140k16 gold badges424 silver badges364 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

TGH · Accepted Answer · 2012-06-05 05:48:54Z

2

Try this

var customer = (from c in _data.Customer
               where c.Name == cells[0]
               select c).FirstOrDefault();

if (customer == null)
    customer = new Customer(...);

answered Jun 5, 2012 at 5:48

TGH

39.4k13 gold badges106 silver badges140 bronze badges

2 Comments

TGH Over a year ago

If you need to ensure that there is at most one record returned you should use SingelOrDefault instead of FirstOrDefault

Laurens Over a year ago

Thanks for the swift response! That did it as well! :-)

Collectives™ on Stack Overflow

Finding or creating an object in Entity Framework

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related