参照完整性违规

Question

I´m getting the next error message:

System.Data.Entity.Infrastructure.DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'

Basically I have two classes, Type and Device.

public class Device
{
    [Key]
    public int DeviceID { get; set; }
    public string Name { get; set; }
    public virtual Type DeviceType { get; set; 
}

and:

public class Type
{
    [Key]
    public string TypeName { get; set; }
}

How can I delete a Type in my programm without having problems with the databases?

Answer 1

您必须先删除使用该类型的所有设备...或先禁用外键

Answer 2

You have a foreign key between Device and Type . Depending on how you have set it up, a device may or may not have a type, but once a device has a type, your database will not allow you to delete that type , because what would the type of that device be then?

Your options are:

• Do not delete types. Just add a boolean field to note whether the type is active or not.

• Delete types only after you updates all devices with what you want (set them to no type? Delete them too?)