Question

我试图将Entity Framework Core示例翻译为F＃。主要是我创建了类BloggingContext，Blog和Post的F＃版本，如下所示：

namespace ConsoleApp.SQLite.FSharp

open Microsoft.EntityFrameworkCore
open System.Collections.Generic

type Post() =
    member val PostId = 0 with get,set
    member val Title = "" with get,set
    member val Content = "" with get,set
    member val BlogId = 0 with get,set
    member val Blog = Blog() with get,set

and Blog() =
    member val BlogId = 0 with get,set
    member val Url = "" with get,set
    member val Posts = [Post()] with get,set

type BloggingContext() =
    inherit DbContext()

    member val Blogs : DbSet<Blog> = null with get,set
    member val Posts : DbSet<Post> = null with get,set

    override this.OnConfiguring optionsBuilder =
        optionsBuilder.UseSqlite("Data Source=blogging.db") |> ignore

然后，我尝试创建Main类的f＃版本，我写的如下：

open System
open ConsoleApp.SQLite.FSharp

[<EntryPoint>]
let main argv =
    let db = new BloggingContext() in
    let blog = Blog() in
    printfn "%s" "Stopped working before here";
    blog.Url <- "http://blogs.msdn.com/adonet";
    db.Blogs.Add(blog) |> ignore;
    let count : int = db.SaveChanges() in
    printfn "%i records saved to database" count;
    printfn "All blogs in database:"
    for blog in db.Blogs do
        printfn "- %s" blog.Url
    0

因为它在代码中被标记，它只是在这行代码let blog = Blog() in之后停止打印任何内容（以及停止工作）并且我不知道我做错了什么创建一个Blog实例。

Answer 1

我通过删除

行中的Post()来解决此问题

member val Posts = [Post()] with get,set

然后

member val Posts = [] with get,set

问题是类声明中的冗余，我正在创建一个已经有一个成员的列表，这不是我想要的。

类实例化后，F＃代码不起作用

1 个答案: