我有以下实体框架代码第一个代码.创建表并插入数据.但是俱乐部表中有重复的记录.
我的业务是：
>使用俱乐部创建应用程序创建俱乐部
>使用人物应用程序创建人物
如何避免重复输入？
static void Main(string[] args)
{
Database.SetInitializer<NerdDinners>(new MyInitializer());
CreateClubs();
InsertPersons();
}
public static void CreateClubs()
{
string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
using (var db = new NerdDinners(connectionstring))
{
Club club1 = new Club();
club1.ClubName = "club1";
Club club2 = new Club();
club2.ClubName = "club2";
Club club3 = new Club();
club3.ClubName = "club3";
db.Clubs.Add(club1);
db.Clubs.Add(club2);
db.Clubs.Add(club3);
int recordsAffected = db.SaveChanges();
}
}
public static Club GetClubs(string clubName)
{
string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
using (var db = new NerdDinners(connectionstring))
{
//var query = db.Clubs.Where(p => p.ClubName == clubName);
var query = db.Clubs.SingleOrDefault(p => p.ClubName == clubName);
return query;
}
}
public static void InsertPersons()
{
string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
using (var db = new NerdDinners(connectionstring))
{
Club club1 = GetClubs("club1");
Club club2 = GetClubs("club2");
Club club3 = GetClubs("club3");
Person p1 = new Person();
p1.PersonName = "Person1";
Person p2 = new Person();
p2.PersonName = "Person2";
List<Club> clubsForPerson1 = new List<Club>();
clubsForPerson1.Add(club1);
clubsForPerson1.Add(club3);
List<Club> clubsForPerson2 = new List<Club>();
clubsForPerson2.Add(club2);
clubsForPerson2.Add(club3);
p1.Clubs = clubsForPerson1;
p2.Clubs = clubsForPerson2;
db.Persons.Add(p1);
db.Persons.Add(p2);
int recordsAffected = db.SaveChanges();
}
}
域
public class Person
{
public int PersonId { get; set; }
public string PersonName { get; set; }
public virtual ICollection<Club> Clubs { get; set; }
}
public class Club
{
public int ClubId { get; set; }
public string ClubName { get; set; }
public virtual ICollection<Person> Members { get; set; }
}
//System.Data.Entity.DbContext is from EntityFramework.dll
public class NerdDinners : System.Data.Entity.DbContext
{
public NerdDinners(string connString): base(connString)
{
}
protected override void OnModelCreating(DbModelBuilder modelbuilder)
{
//Fluent API - Plural Removal
modelbuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
public DbSet<Person> Persons { get; set; }
public DbSet<Club> Clubs { get; set; }
}
解决方法
问题是您创建更多的上下文.
首先你创建俱乐部.没关系.但是,当您创建人员时,您可以通过GetClubs获取俱乐部,但是对于每个俱乐部,您将处理实际的实体框架上下文,以便最终分离实体.在InsertPersons,你添加了离散的俱乐部实体给新的人,所以实际上下文会认为俱乐部是新的俱乐部.
所以当你为一个人添加一个俱乐部,你实际上创建了新的俱乐部.
这是因为实体框架跟踪更改并管理每个上下文的实体.如果您将实体添加到不包含它的上下文中,那么它将像新实体一样对待.
其实你应该这样做(未测试)：
static void Main(string[] args)
{
Database.SetInitializer<NerdDinners>(new MyInitializer());
string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
using (var db = new NerdDinners(connectionstring))
{
CreateClubs(db);
InsertPersons(db);
}
}
public static void CreateClubs(NerdDinners db)
{
Club club1 = new Club();
club1.ClubName = "club1";
Club club2 = new Club();
club2.ClubName = "club2";
Club club3 = new Club();
club3.ClubName = "club3";
db.Clubs.Add(club1);
db.Clubs.Add(club2);
db.Clubs.Add(club3);
int recordsAffected = db.SaveChanges();
}
public static Club GetClubs(string clubName,NerdDinners db)
{
//var query = db.Clubs.Where(p => p.ClubName == clubName);
var query = db.Clubs.SingleOrDefault(p => p.ClubName == clubName);
return query;
}
public static void InsertPersons(NerdDinners db)
{
Club club1 = GetClubs("club1",db);
Club club2 = GetClubs("club2",db);
Club club3 = GetClubs("club3",db);
Person p1 = new Person();
p1.PersonName = "Person1";
Person p2 = new Person();
p2.PersonName = "Person2";
List<Club> clubsForPerson1 = new List<Club>();
clubsForPerson1.Add(club1);
clubsForPerson1.Add(club3);
List<Club> clubsForPerson2 = new List<Club>();
clubsForPerson2.Add(club2);
clubsForPerson2.Add(club3);
p1.Clubs = clubsForPerson1;
p2.Clubs = clubsForPerson2;
db.Persons.Add(p1);
db.Persons.Add(p2);
int recordsAffected = db.SaveChanges();
}
当然,你应该重构这个代码的结构,但请注意,我的操作只使用一个EF上下文.
