常见问题
出现错误提示: Specified key was too long;max key length is 767 bytes
1)查看实体的字符串类型属性是否设置了长度
2)MyContext 类中是否声明为生成为mysql 数据类型的 [DbConfigurationType(typeof(MySqlEFConfiguration))]
出现错误提示: Model compatibility cannot be checked because the database does not contain model metadata
删除已生成的数据库后重新运行程序
出现错误提示:序列不包含任何匹配元素
检查一下:
例如:1.
public class Employee { [Key] public int EmployeeId { get; set; } public string Name { get; set; } [ForeignKey("ManagerId")] public Employee Manager { get; set; } public int ManagerId { get; set; } } [ForeignKey("ManagerId")] public Employee Manager { get; set; } public int ManagerId { get; set; } 这个外键设置。 |
2.
[Column(TypeName="VARCHAR(254)")] public string ColumnName { get; set; } 这样的定义,改成: [MaxLength(254)] [Column(TypeName="VARCHAR")] public string ColumnName { get; set; } |
3.(以下代码未测试,因为我不是这样用的,在下篇文章中将进行测试)
modelBuilder.Entity<Category>() .HasKey(c => c.IdCategory ) .HasOptional(p => p.Children) .WithMany() .HasForeignKey(c => c.ChildrenId); 改成: modelBuilder.Entity<Category>() .HasKey(c => c.IdCategory ) .HasMany(p => p.Children) .WithOptional() .HasForeignKey(c => c.ChildrenId); .WithMany()换成.WithOptional() |