问多线程EF6中的主密钥冲突

EN

class Program
{
    private static ManualResetEvent resetEvent;
    private static int nIncompleteThreads = 0;

    //Call this function to add to the dbo.Items table
    private static void AddItems(object response)
    {
        string strResponse = (string)response;

        using (GWDBContext ctx = new GWDBContext())
        {
            IEnumerable<Items> itemResponse = JsonConvert.DeserializeObject<IEnumerable<Items>>(strResponse);

            ctx.Items.AddRange(itemResponse);
            ctx.SaveChanges();
        }

        if (Interlocked.Decrement(ref nIncompleteThreads) == 0)
        {
            resetEvent.Set();
        }
    }

    //Call this function to add to the dbo.Recipes table
    private static void AddRecipes(object response)
    {
        string strResponse = (string)response;

        using (GWDBContext ctx = new GWDBContext())
        {
            IEnumerable<Recipes> recipeResponse = JsonConvert.DeserializeObject<IEnumerable<Recipes>>(strResponse);

            ctx.Recipes.AddRange(recipeResponse);

            foreach(Recipes recipe in recipeResponse)
            {
                ctx.Ingredients.AddRange(recipe.ingredients);
            }
            ctx.SaveChanges(); //This is where the error is thrown
        }

        if (Interlocked.Decrement(ref nIncompleteThreads) == 0)
        {
            resetEvent.Set();
        }
    }

    static void GetResponse(string strLink, string type)
    {
        //This method calls the GW2 API through HTTPWebRequest
        //and store the responses in a List<string> responseList variable.
        GWHelper.GetAllResponses(strLink);

        resetEvent = new ManualResetEvent(false);
        nIncompleteThreads = GWHelper.responseList.Count();

        //ThreadPool.QueueUserWorkItem creates threads for multi-threading
        switch (type)
        {
            case "I":
                {
                    foreach (string strResponse in GWHelper.responseList)
                    {
                        ThreadPool.QueueUserWorkItem(new WaitCallback(AddItems), strResponse);
                    }
                    break;
                }
            case "R":
                {
                    foreach (string strResponse in GWHelper.responseList)
                    {
                        ThreadPool.QueueUserWorkItem(new WaitCallback(AddRecipes), strResponse);
                    }
                    break;
                }
        }

        //Waiting then resetting event and clearing the responseList
        resetEvent.WaitOne();           
        GWHelper.responseList.Clear();
        resetEvent.Dispose();
    }

    static void Main(string[] args)
    {
        string strItemsLink = "items";
        string strRecipesLink = "recipes";

        GetResponse(strItemsLink, "I");
        GetResponse(strRecipesLink, "R");

        Console.WriteLine("Press any key to continue...");
        Console.ReadLine();
    }

public class GWDBContext : DbContext
{
    public GWDBContext() : base("name=XenoGWDBConnectionString") { }

    public DbSet<Items> Items { get; set; }
    public DbSet<Recipes> Recipes { get; set; }
    public DbSet<Ingredient> Ingredients { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
    }
}

public class Items
{
    public Items()
    {
        Recipes = new HashSet<Recipes>();
        Ingredients = new HashSet<Ingredient>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)] //This attribute makes sure that the id column is not an identity column since the api is sending that).
    public int id { get; set; }

    .../...
    public virtual ICollection<Recipes> Recipes { get; set; }
    public virtual ICollection<Ingredient> Ingredients { get; set; }
}

public class Recipes
{
    public Recipes()
    {
        disciplines = new List<string>();
        ingredients = new HashSet<Ingredient>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)] //This attribute makes sure that the id column is not an identity column since the api is sending that).
    public int id { get; set; }
    public string type { get; set; }

    [ForeignKey("Items")] //This attribute points the output_item_id column to the Items table.

    .../...
    private List<string> _disciplines { get; set; }
    public List<string> disciplines
    {
        get { return _disciplines; }
        set { _disciplines = value; }
    }

    [Required]
    public string DisciplineAsString
    {
        //get; set;
        get { return string.Join(",", _disciplines); }
        set { _disciplines = value.Split(',').ToList(); }
    }

    public string chat_link { get; set; }

    public virtual ICollection<Ingredient> ingredients { get; set; }
    public virtual Items Items { get; set; }
}

public class Ingredient
{
    public Ingredient()
    {
        Recipe = new HashSet<Recipes>();
    }

    [Key]
    public int ingredientID { get; set; }

    [ForeignKey("Items")] //This attribute points the item_id column to the Items table.
    public int item_id { get; set; }
    public int count { get; set; }

    public virtual ICollection<Recipes> Recipe { get; set; }
    public virtual Items Items { get; set; }
}