C# · 12月 27, 2021

c# – EF Code First中自引用实体的映射

在我的数据库中,我有一个表类别,列ID,CategoryName,ParentCategoryId,其中ParentCategoryId对Category.Id有约束.

我首先使用实体​​框架代码,实体看起来像:

public class Category{ public long Id { get; private set; } public string CategoryName { get; private set; } public long? ParentCategoryId { get; private set; } public Category ParentCategory { get; private set; } public virtual ICollection<Category> SubCategories { get; private set; }}

如果我尝试对此运行查询,我会得到异常:

The relationship ‘ComplaintModel.FK_Complaint_Category’ was not loaded because the type ‘ComplaintModel.Category’ is not available.\r\nThe following information may be useful in resolving the prevIoUs error:\r\nThe required property ‘Category1’ does not exist on the type ‘EC.Complaint.Services.Command.Domain.Entities.Category’.\r\n\r\n”} System.Exception {System.Data.MetadataException}

所以它似乎需要导航属性,如果我添加这些:

public ICollection<Category> Category1 { get; private set; } public long? Category2Id { get; private set; } public Category Category2 { get; private set; }

查询有效.

但是,当然,我不想要Category1和Category2属性,我想要使用ParentCategory和SubCategories属性.

如何告诉代码首先使用正确的导航属性?

解决方法 你的POCO课应该是这样的…… public class Category{ public long Id { get; private set; } public string CategoryName { get; private set; } public long? ParentCategoryId { get; private set; } public virtual Category ParentCategory { get; private set; } public virtual ICollection<Category> SubCategories { get; private set; }}public class CategoryConfiguration : EntityTypeConfiguration<Category>{ public CategoryConfiguration() { this.HasKey(x => x.Id); this.HasMany(category => category.SubCategories) .WithOptional(category => category.ParentCategoryId) .HasForeignKey(course => course.UserId) .WillCascadeOnDelete(false); }}