我有以下实体框架代码第一代码。创建表并插入数据。但是 Club 表中有重复的记录。
我的操作是:-
使用俱乐部创建应用程序创建俱乐部
使用人员应用程序创建人员
如何避免重复录入?
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();
}
}
Domain
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; }
}
问题是你创建了更多的上下文。
首先,您创建俱乐部。没关系。但是当你创建人员时,你可以通过以下方式获取俱乐部GetClubs
,但是对于每个俱乐部,您都会配置实际的实体框架上下文,因此最终会得到分离的实体。在InsertPersons
您将独立的俱乐部实体添加到新人员中,因此实际上下文会认为这些俱乐部是新俱乐部。
因此,当您向某人添加俱乐部时,您实际上创建了新俱乐部。
这是因为实体框架跟踪更改并管理每个上下文的实体。如果您将一个实体添加到尚未包含该实体的上下文中,那么它将被视为一个新实体。
实际上,你应该这样做(未经测试):
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,您应该重构此代码的结构,但请注意,我的操作仅使用一个 EF 上下文。
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