今天在编写DomainModel和DomainMapper,最后放到OnModelCreating中运行的时候,给我抛出了如下错误:
One or more validation errors were detected during model generation: TinyFrame.Data.DataContext.t_expert_content_ExpertType: : Multiplicity conflicts with the referential constraint in Role 't_expert_content_ExpertType_Target' in relationship 't_expert_content_ExpertType'. Because all of the properties in the Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'.
排查了一会儿找到了原因所在。
请看我的Model:
public class t_expert_content { public string ID { get; set; } //PK public string TypeID { get; set; } public string Name { get; set; } //问题标题 public string Publisher { get; set; } //发布人 public int? Count { get; set; } //查看次数 public bool IsCheck { get; set; } //是否审核 public DateTime PublishDate { get; set; } //发布时间 public string Content { get; set; } public int? Order { get; set; } public virtual t_expert_type ExpertType { get; set; } }
然后是ModelMapper:
public class t_expert_content_mapper : EntityTypeConfiguration<t_expert_content> { public t_expert_content_mapper() { this.ToTable("t_expert_content"); this.HasKey(x => x.ID); this.Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None); this.Property(x => x.ID).HasMaxLength(36); this.Property(x => x.TypeID).IsRequired().HasMaxLength(36); this.Property(x => x.Name).IsRequired().HasMaxLength(500); this.Property(x => x.Publisher).IsOptional().HasMaxLength(150); this.Property(x => x.Count).IsOptional(); this.Property(x => x.IsCheck).IsRequired(); this.Property(x => x.PublishDate).IsRequired(); this.Property(x => x.Content).IsOptional().HasColumnType("text"); this.Property(x => x.Order).IsOptional(); this.HasOptional(x => x.ExpertType) .WithMany() .HasForeignKey(x => x.TypeID) .WillCascadeOnDelete(false); } }
看上去没啥问题,但是问题就出在外键映射上面。
由于t_expert_content的外键TypeID 是t_expert_type表中的主键ID。由于我在映射的时候,写的是:
this.Property(x => x.TypeID).IsRequired().HasMaxLength(36);
而在下面进行导航属性指定的时候,ExpertType被指定成了HasOptional类型的:
this.HasOptional(x => x.ExpertType) .WithMany() .HasForeignKey(x => x.TypeID) .WillCascadeOnDelete(false);
导致二者产生了冲突,抛出了开头的错误。
知道了原因,解决方法就好办了:
public class t_expert_content_mapper : EntityTypeConfiguration<t_expert_content> { public t_expert_content_mapper() { this.ToTable("t_expert_content"); this.HasKey(x => x.ID); this.Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None); this.Property(x => x.ID).HasMaxLength(36); //this.Property(x => x.TypeID).IsRequired().HasMaxLength(36); this.Property(x => x.Name).IsRequired().HasMaxLength(500); this.Property(x => x.Publisher).IsOptional().HasMaxLength(150); this.Property(x => x.Count).IsOptional(); this.Property(x => x.IsCheck).IsRequired(); this.Property(x => x.PublishDate).IsRequired(); this.Property(x => x.Content).IsOptional().HasColumnType("text"); this.Property(x => x.Order).IsOptional(); this.HasRequired(x => x.ExpertType) .WithMany() .HasForeignKey(x => x.TypeID) .WillCascadeOnDelete(false); } }
需要说明的是,上面代码中的:
this.Property(x => x.TypeID).IsRequired().HasMaxLength(36);
可以选择注释,也可以选择不注释。