c# - Finding or creating an object in Entity Framework -

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my domain model , associations follows:

  • customer has many regions
  • region has many locations

our client supplies csv file has following columns:

  • customer name
  • region name
  • location name
    • latitude
    • longitude
    • ...

based on information, have find or create customer name, find or create region name, , find or update location name.

i have tried following:

var customer = c in _data.customer                c.name == cells[0]                select c;  if (customer == null)     customer = new customer(...);

i follow same pattern finding or creating/updating region , location, however, problem run type of linq query cannot converted customer-object on line customer = new customers();. need reference customer object later can't have 2 separate variables.

how accomplish in entity framework?

this code 

var customer = c in _data.customer                c.name == cells[0]                select c;

returns customers has name equals cells[0] return type iqueryable<customer> not sigle customer (that's why customer = new customer(...) doesn't work).

what need call firstordefault or singleordefault (depending on requirements.) on if want have 1 customer.

so should work

var customer = (from c in _data.customer                c.name == cells[0]                select c).singleordefault();

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