我有一个Auto-identity (int)
列的实体。作为数据种子的一部分,我想在系统中使用“标准数据”的特定标识符值,之后我想让数据库对id值进行排序。
到目前为止,我已经能够将IDENTITY_INSERT
设置为On作为插入批处理的一部分,但实体框架不会生成包含Id
的插入语句。这是有道理的,因为模型认为数据库应该提供值,但在这种情况下,我想提供值。
模型(伪代码):
public class ReferenceThing
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id{get;set;}
public string Name{get;set;}
}
public class Seeder
{
public void Seed (DbContext context)
{
var myThing = new ReferenceThing
{
Id = 1,
Name = "Thing with Id 1"
};
context.Set<ReferenceThing>.Add(myThing);
context.Database.Connection.Open();
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing ON")
context.SaveChanges(); // <-- generates SQL INSERT statement
// but without Id column value
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing OFF")
}
}
任何人都可以提供任何见解或建议吗?
答案 0 :(得分:10)
所以我可能通过生成我自己的包含Id列的SQL插入语句来解决这个问题。这感觉就像一个可怕的黑客,但它确实有效: - /
public class Seeder
{
public void Seed (DbContext context)
{
var myThing = new ReferenceThing
{
Id = 1,
Name = "Thing with Id 1"
};
context.Set<ReferenceThing>.Add(myThing);
context.Database.Connection.Open();
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing ON")
// manually generate SQL & execute
context.Database.ExecuteSqlCommand("INSERT ReferenceThing (Id, Name) " +
"VALUES (@0, @1)",
myThing.Id, myThing.Name);
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing OFF")
}
}
答案 1 :(得分:7)
我为DbContext
创建了一个替代构造函数,它使用了一个bool allowIdentityInserts
。我将该bool设置为DbContext
上的同名私有字段。
如果我在“模式”中创建上下文,则我的OnModelCreating
然后“取消指定”身份规范
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
if(allowIdentityInsert)
{
modelBuilder.Entity<ChargeType>()
.Property(x => x.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
这允许我插入Ids而不更改我的实际数据库标识规范。我仍然需要使用你所做的身份插入开/关技巧,但至少EF会发送Id值。
答案 2 :(得分:4)
如果您使用数据库优先模型,则应将ID列的 StoreGeneratedPattern 属性从Identity更改为无。
之后,当我回复here时,这应该会有所帮助:
using (var transaction = context.Database.BeginTransaction())
{
var myThing = new ReferenceThing
{
Id = 1,
Name = "Thing with Id 1"
};
context.Set<ReferenceThing>.Add(myThing);
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing ON");
context.SaveChanges();
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT ReferenceThing OFF");
transaction.Commit();
}
答案 3 :(得分:2)
如果没有第二个EF级别模型,则无法完成 - 复制种子的类。
正如您所说 - 您的元数据表明数据库提供的值是播种期间不存在的值。
答案 4 :(得分:2)
根据之前的Question,您需要开始上下文的交易。保存更改后,您还必须重新标识“身份插入”列,最后必须提交事务。
using (var transaction = context.Database.BeginTransaction())
{
var item = new ReferenceThing{Id = 418, Name = "Abrahadabra" };
context.IdentityItems.Add(item);
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT Test.Items ON;");
context.SaveChanges();
context.Database.ExecuteSqlCommand("SET IDENTITY_INSERT [dbo].[User] OFF");
transaction.Commit();
}
答案 5 :(得分:1)
在尝试了本网站上的几个选项后,以下代码对我有用( EF 6 )。请注意,如果项目已存在,它首先尝试正常更新。如果没有,则尝试正常插入,如果错误是由IDENTITY_INSERT引起的,则尝试解决方法。另请注意,db.SaveChanges将失败,因此db.Database.Connection.Open()语句和可选的验证步骤。请注意,这不是更新上下文,但在我的情况下,没有必要。希望这有帮助!
public static bool UpdateLeadTime(int ltId, int ltDays)
{
try
{
using (var db = new LeadTimeContext())
{
var result = db.LeadTimes.SingleOrDefault(l => l.LeadTimeId == ltId);
if (result != null)
{
result.LeadTimeDays = ltDays;
db.SaveChanges();
logger.Info("Updated ltId: {0} with ltDays: {1}.", ltId, ltDays);
}
else
{
LeadTime leadtime = new LeadTime();
leadtime.LeadTimeId = ltId;
leadtime.LeadTimeDays = ltDays;
try
{
db.LeadTimes.Add(leadtime);
db.SaveChanges();
logger.Info("Inserted ltId: {0} with ltDays: {1}.", ltId, ltDays);
}
catch (Exception ex)
{
logger.Warn("Error captured in UpdateLeadTime({0},{1}) was caught: {2}.", ltId, ltDays, ex.Message);
logger.Warn("Inner exception message: {0}", ex.InnerException.InnerException.Message);
if (ex.InnerException.InnerException.Message.Contains("IDENTITY_INSERT"))
{
logger.Warn("Attempting workaround...");
try
{
db.Database.Connection.Open(); // required to update database without db.SaveChanges()
db.Database.ExecuteSqlCommand("SET IDENTITY_INSERT[dbo].[LeadTime] ON");
db.Database.ExecuteSqlCommand(
String.Format("INSERT INTO[dbo].[LeadTime]([LeadTimeId],[LeadTimeDays]) VALUES({0},{1})", ltId, ltDays)
);
db.Database.ExecuteSqlCommand("SET IDENTITY_INSERT[dbo].[LeadTime] OFF");
logger.Info("Inserted ltId: {0} with ltDays: {1}.", ltId, ltDays);
// No need to save changes, the database has been updated.
//db.SaveChanges(); <-- causes error
}
catch (Exception ex1)
{
logger.Warn("Error captured in UpdateLeadTime({0},{1}) was caught: {2}.", ltId, ltDays, ex1.Message);
logger.Warn("Inner exception message: {0}", ex1.InnerException.InnerException.Message);
}
finally
{
db.Database.Connection.Close();
//Verification
if (ReadLeadTime(ltId) == ltDays)
{
logger.Info("Insertion verified. Workaround succeeded.");
}
else
{
logger.Info("Error!: Insert not verified. Workaround failed.");
}
}
}
}
}
}
}
catch (Exception ex)
{
logger.Warn("Error in UpdateLeadTime({0},{1}) was caught: {2}.", ltId.ToString(), ltDays.ToString(), ex.Message);
logger.Warn("Inner exception message: {0}", ex.InnerException.InnerException.Message);
Console.WriteLine(ex.Message);
return false;
}
return true;
}
答案 6 :(得分:1)
尝试将此代码添加到您的数据库上下文&#34;以保持其清洁&#34;可以这么说:
用法场景示例(将ID 0默认记录添加到实体类型ABCStatus:
protected override void Seed(DBContextIMD context)
{
bool HasDefaultRecord;
HasDefaultRecord = false;
DBContext.ABCStatusList.Where(DBEntity => DBEntity.ID == 0).ToList().ForEach(DBEntity =>
{
DBEntity.ABCStatusCode = @"Default";
HasDefaultRecord = true;
});
if (HasDefaultRecord) { DBContext.SaveChanges(); }
else {
using (var dbContextTransaction = DBContext.Database.BeginTransaction()) {
try
{
DBContext.IdentityInsert<ABCStatus>(true);
DBContext.ABCStatusList.Add(new ABCStatus() { ID = 0, ABCStatusCode = @"Default" });
DBContext.SaveChanges();
DBContext.IdentityInsert<ABCStatus>(false);
dbContextTransaction.Commit();
}
catch (Exception ex)
{
// Log Exception using whatever framework
Debug.WriteLine(@"Insert default record for ABCStatus failed");
Debug.WriteLine(ex.ToString());
dbContextTransaction.Rollback();
DBContext.RollBack();
}
}
}
}
为获取表名扩展方法
添加此帮助程序类public static class ContextExtensions
{
public static string GetTableName<T>(this DbContext context) where T : class
{
ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;
return objectContext.GetTableName<T>();
}
public static string GetTableName<T>(this ObjectContext context) where T : class
{
string sql = context.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex(@"FROM\s+(?<table>.+)\s+AS");
Match match = regex.Match(sql);
string table = match.Groups["table"].Value;
return table;
}
}
要添加到DBContext的代码:
public MyDBContext(bool _EnableIdentityInsert)
: base("name=ConnectionString")
{
EnableIdentityInsert = _EnableIdentityInsert;
}
private bool EnableIdentityInsert = false;
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
Database.SetInitializer(new MigrateDatabaseToLatestVersion<DBContextIMD, Configuration>());
//modelBuilder.Entity<SomeEntity>()
// .Property(e => e.SomeProperty)
// .IsUnicode(false);
// Etc... Configure your model
// Then add the following bit
if (EnableIdentityInsert)
{
modelBuilder.Entity<SomeEntity>()
.Property(x => x.ID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
modelBuilder.Entity<AnotherEntity>()
.Property(x => x.ID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
//Add this for Identity Insert
/// <summary>
/// Enable Identity insert for specified entity type.
/// Note you should wrap the identity insert on, the insert and the identity insert off in a transaction
/// </summary>
/// <typeparam name="T">Entity Type</typeparam>
/// <param name="On">If true sets identity insert on else set identity insert off</param>
public void IdentityInsert<T>(bool On)
where T: class
{
if (!EnableIdentityInsert)
{
throw new NotSupportedException(string.Concat(@"Cannot Enable entity insert on ", typeof(T).FullName, @" when _EnableIdentityInsert Parameter is not enabled in constructor"));
}
if (On)
{
Database.ExecuteSqlCommand(string.Concat(@"SET IDENTITY_INSERT ", this.GetTableName<T>(), @" ON"));
}
else
{
Database.ExecuteSqlCommand(string.Concat(@"SET IDENTITY_INSERT ", this.GetTableName<T>(), @" OFF"));
}
}
//Add this for Rollback changes
/// <summary>
/// Rolls back pending changes in all changed entities within the DB Context
/// </summary>
public void RollBack()
{
var changedEntries = ChangeTracker.Entries()
.Where(x => x.State != EntityState.Unchanged).ToList();
foreach (var entry in changedEntries)
{
switch (entry.State)
{
case EntityState.Modified:
entry.CurrentValues.SetValues(entry.OriginalValues);
entry.State = EntityState.Unchanged;
break;
case EntityState.Added:
entry.State = EntityState.Detached;
break;
case EntityState.Deleted:
entry.State = EntityState.Unchanged;
break;
}
}
}
答案 7 :(得分:1)
对于将来的Google员工,我发现了答案,表明OnModelCreating()
中的某些条件逻辑对我不起作用。
此方法的主要问题是EF缓存模型,因此无法在同一应用程序域中打开或关闭身份。
我们采用的解决方案是创建第二个派生的DbContext
,它允许标识插入。这样,两个模型都可以缓存,并且在特殊(希望是)极少数情况下,当您需要插入标识值时,可以使用派生的DbContext
。
从@RikRak的问题中得出以下几点:
public class ReferenceThing
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Name { get; set; }
}
public class MyDbContext : DbContext
{
public DbSet<ReferenceThing> ReferenceThing { get; set; }
}
我们添加了此派生的DbContext
:
public class MyDbContextWhichAllowsIdentityInsert : MyDbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<ReferenceThing>()
.Property(x => x.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
然后将其与Seeder
一起使用,如下所示:
var specialDbContext = new MyDbContextWhichAllowsIdentityInsert();
Seeder.Seed(specialDbContext);
答案 8 :(得分:1)
假设您有一个名为 Branch 的表,该表具有一个名为 BranchId 的整数类型的列。 按照与SQL Server的约定,EF将假定类型为integer的列为Identity列。
因此它将自动将列的 身份规范 设置为:
如果您要为具有指定ID值的实体播种,请按以下方式使用DatabaseGeneratedOption:
public class Branch
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int BranchId { get; set; }
public string Description { get; set; }
}
然后,您可以播种数据并将所需的任何值分配给 BranchId 。