C#设置外键

Question

我有一个表单可以将主人和宠物的数据输入数据库。宠物有一个主人id的外键，主人和宠物的数据填在同一个表格里，那么宠物对象中没有设置ownerID怎么设置宠物对象的主人id数据库了吗？或者我必须先在数据库中设置所有者？

Class Owner 属性

private int32 idOwner;
private String name;

Class Pet 属性；

private int32 Pet;
private int32 idOwner;    // foreign key
private String name;

表格

Owner owner = new Owner();
owner.Name = this.ownerNameTxt.Text.Trim();
OwnerService.addOwner(owner); // add owner to database

Pet pet = new Pet();
pet.name = this.petNameTxt.Text.Trim();
pet.idOwner = ????????

Answer 1

所以你有一个标识列 idOwner，它在插入时生成，你想在 Pet 对象中设置该标识。然后，您需要修改 OwnerService.addOwner 方法，以便 select 从数据库中生成 ID 并更新所有者对象。

private void addOwner(owner)
{
    // your current logic here but modify to
    // add  ;SELECT  SCOPE_IDENTITY(); at the end of your insert query.
    // and store it in a local int. eg int ownerID = (int)cmd.ExecuteScalar();

    owner.idOwner = ownerID;
}

然后你的表单代码：

Owner owner = new Owner();
owner.Name = this.ownerNameTxt.Text.Trim();
OwnerService.addOwner(owner); // add owner to database

Pet pet = new Pet();
pet.name = this.petNameTxt.Text.Trim();
pet.idOwner = owner.idOwner;

SCOPE_IDENTITY (Transact-SQL) 的文档：

Returns the last identity value inserted into an identity column in the same scope. A scope is a module: a stored procedure, trigger, function, or batch. Therefore, two statements are in the same scope if they are in the same stored procedure, function, or batch.

C#设置外键

C# setting foreign key

c#

winforms

persistence