Exception with optional navigation properties #29

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1. simon-reynolds

   self-assigned this

   on May 1, 2019
2. bricelam commented on May 2, 2019

   

   bricelam

   on May 2, 2019

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   cc @AndriySvyryd in case he has any pointers
3. AndriySvyryd commented on May 2, 2019

   

   AndriySvyryd

   on May 2, 2019

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   We would need to add explicit support for this in Core to get a nice experience.
   The best workaround I can think of is to use a Nullable private field that is wrapped by the optional property. Then configure the relationship to use the field and ignore the property.
4. simon-reynolds commented on Mar 18, 2021

   

   simon-reynolds

   on Mar 18, 2021

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   Nullable private fields wouldn't be able to work on an F# record types, similar to C# records, private fields do not exist in them

   Given that C# records are now a thing, and reference types in C# can now be annotated in not nullable, is there any support for optional types similar to what is planned for record types in dotnet/efcore#11457?

   👍React with 👍1Reacted by Lucas Teles
5. simon-reynolds commented on Apr 4, 2021

   

   simon-reynolds

   on Apr 4, 2021

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   Seems like this could be solved by dotnet/efcore#22542

   👀React with 👀1Reacted by Lucas Teles
6. LiteracyFanatic commented on Jul 9, 2021

   

   LiteracyFanatic

   on Jul 9, 2021

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   Thought I would post a small working sample since it took me a while to figure out how exactly

   The best workaround I can think of is to use a Nullable private field that is wrapped by the optional property. Then configure the relationship to use the field and ignore the property.

   translates to code.

   [<AllowNullLiteral>]
   type Comment() =
       [<DefaultValue>] val mutable private _Id: int
       // Backing field is a regular class which can be null
       [<DefaultValue>] val mutable private _Parent: Comment
       [<DefaultValue>] val mutable private _Text: string
       member this.Id with get() = this._Id and set v = this._Id <- v
       // Property is converted to and from Option
       member this.Parent with get() = Option.ofObj this._Parent and set v = this._Parent <- Option.toObj v
       member this.Text with get() = this._Text and set v = this._Text <- v
   
   type CommentContext =
       inherit DbContext
   
       [<DefaultValue>] val mutable private _Comments: DbSet<Comment>
       member this.Comments with get() = this._Comments and set v = this._Comments <- v
   
       override this.OnModelCreating(modelBuilder: ModelBuilder) =
   
               member this.Configure(builder) =
                   // Tell EF Core to ignore the property and use the field directly for the relationship
                   builder.Ignore("Parent")
                       |> ignore
                   
                   builder.HasOne("_Parent")
                       .WithMany()
                       // Set the key you want to appear in the database
                       .HasForeignKey("ParentId")
                       |> ignore