C# 实体框架6.x代码第一主键约束错误保存多对多字段

我首先使用代码，并尝试添加共享同一facet对象的两条记录。EF尝试两次添加相同的共享对象，因此我得到了违反主键约束的错误。考虑这个…

XML

配方和方面有多对多的关系

public class Recipe
{
    [Key]
    public int Recipe_id { get; set; }  
    public string Author { get; set; }
    public DateTime CreatedDate { get; set; }
    public string Description { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Facet> Facets { get; set; }
}

//Facet needs to have a unique taxonomy id and name combination
public class Facet
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Facet_id { get; set; }

    [Key]
    [Column(Order = 0)]
    public int Taxonomy_id { get; set; }

    [Key]
    [Column(Order = 1)]
    [StringLength(500)]
    public string Name { get; set; }

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

public class RecipeContext : DbContext
{
    public RecipeContext() : base("name=RecipeContextConn")
    {
        Database.SetInitializer<RecipeContext>(new CreateDatabaseIfNotExists<RecipeContext>());
    }

    public DbSet<Recipe> Recipe { get; set; }
    public DbSet<Facet> Facet { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
    }
}

// Automapper configuration
var config = new MapperConfiguration(cfg =>
{
    cfg.CreateMap<RecipeElement, Recipe>()
        .ForMember(dest => dest.Facets, opt => opt.MapFrom(src => src.Facet));

    cfg.CreateMap<FacetElement, Facet>();
});

Mapper = config.CreateMapper();

我的代码在Foreach循环后保存时中断

foreach (var recipeElement in fullRecipeSet.Recipes.Recipe)
{
    // Using Automapper to map from one object to another
    Recipe recipeDto = Mapper.Map<Recipe>(recipeElement);

    ctx.Recipe.Add(recipeDto);
}

ctx.SaveChanges();

---

如何告诉EF只保存一次唯一的方面？

我在这里找到了一些建议

我必须先在DB中保存独特的方面。然后，当我将xml映射到配方时，删除映射的facet并从数据库中分配创建的facet。这确保所有配方共享相同的精确刻面对象

Recipe recipeDto = MapInitializer.Mapper.Map<Recipe>(recipeElement);

var facs = recipeDto.Facets;

// Null out the facets that gets mapped from the xml. 
recipeDto.Facets = new List<Facet>();

// Reassign facet from the db. Otherwise, trying to save the recipe with the 
// facets that was mapped from the xml will cause duplicate facts trying to insert.
foreach (var f in facs)
{
    var dbFacet = ctx.Facet.Where(x => x.Taxonomy_id == f.Taxonomy_id && x.Name == f.Name).First();
    recipeDto.Facets.Add(dbFacet);
}

ctx.Recipe.Add(recipeDto);

---

几年后来到这里，但谢谢你。这救了我。我在拯救许多重复的孩子方面遇到了问题。谢谢

Recipe recipeDto = MapInitializer.Mapper.Map<Recipe>(recipeElement);

var facs = recipeDto.Facets;

// Null out the facets that gets mapped from the xml. 
recipeDto.Facets = new List<Facet>();

// Reassign facet from the db. Otherwise, trying to save the recipe with the 
// facets that was mapped from the xml will cause duplicate facts trying to insert.
foreach (var f in facs)
{
    var dbFacet = ctx.Facet.Where(x => x.Taxonomy_id == f.Taxonomy_id && x.Name == f.Name).First();
    recipeDto.Facets.Add(dbFacet);
}

ctx.Recipe.Add(recipeDto);