How to configure, map One to One Relationship in EF Core

Question

As a student I have to design my first WebApi using .Net Core. I have been searching for two days, and haven't found an answer that solves my problem. Maybe because i'm a beginner.

I have following classes:

public class Boat
{
    public int BoatId { get; set; }
    public int BoatNr { get; set; }
    public string BoatName { get; set; }

    public Location Location { get; set; }
}

public class Location
{
    public int LocationId { get; set; }
    public int Row { get; set; }
    public char Side { get; set; }
    public int Level { get; set; }

    public Boat Boat { get; set; }
}

I want to configure my database, so I can get a list of all the boats, with their location. But I also want a list of all the locations, and if there's a boat, yes or no.

Both properties should be optional in my opinion. A location doesn't necessarily own a boat, and a boat doesn't necessarily have a location.

I've tried:

Entity Framework Core zero-or-one to zero-or-one relation

Implementing Zero Or One to Zero Or One relationship in EF Code first by Fluent API

...but without results

Edit: I would like to have a DbSet Boats that shows all my boats with their locations. And a DbSet Locations, that shows al the locations and their boats.

So what does or doesn't this code do? Can you show your configuration and the code that accesses the database, and explain what you expect to happen and what actually happens? — CodeCaster, Mar 09 '21 at 13:05

Serge · Accepted Answer · 2021-03-09T13:30:37.427

Try this:

public class Boat
{
    public int Id { get; set; }

    public int BoatNr { get; set; }
    public string BoatName { get; set; }

    public int? LocationId { get; set; }
    public virtual Location Location {get; set;}
}

public class Location
{
    public int Id{ get; set; }

    public int Row { get; set; }
    public char Side { get; set; }
    public int Level { get; set; }

    public virtual ICollection<Boat> Boats { get; set; }

    //you can use this instead of collection
    public virtual Boat Boat { get; set; }
    //but I don't recommend to do this
}

and since you are using net core 5 you don't need any fluent apis

Sorry, I made a typo, Storage should have been Location. – Segher Mar 09 '21 at 13:16 — Segher, Mar 09 '21 at 13:16

How to configure, map One to One Relationship in EF Core

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