entity framework 6 can't insert record

Question

if I define a sequence and a table like this:

CREATE SEQUENCE [dbo].[seq-test] 
 AS [bigint]
 START WITH 0
 INCREMENT BY 1
 MINVALUE -9223372036854775808
 MAXVALUE 9223372036854775807
 CACHE 
GO


CREATE TABLE [dbo].[testTab] 
(
    [iden] [bigint] NOT NULL DEFAULT (NEXT VALUE FOR [seq-test]),
    [name1] [nchar](10) NULL,
    [name2] [nchar](10) NULL,
    PRIMARY KEY CLUSTERED 
    (
    [iden] ASC
    )
) ON [PRIMARY]

and then try to insert data using EF 6:

testTab d = new testTab();
d.name1 = "sss";

using (var db = new ABEntities2())
{
    db.testTabs.Add(d);
    db.SaveChanges();
}

and I set StoreGeneratedPattern to Identity for iden column, it doesn't behave as it should, Exception thrown by SaveChanges is DbUpdateConcurrencyException :

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

what am I doing wrong?

generated testTabs:

<EntitySetMapping Name="testTabs">
  <EntityTypeMapping TypeName="ABModel.testTab">
    <MappingFragment StoreEntitySet="testTab">
      <ScalarProperty Name="iden" ColumnName="iden" />
      <ScalarProperty Name="name1" ColumnName="name1" />
      <ScalarProperty Name="name2" ColumnName="name2" />
    </MappingFragment>
  </EntityTypeMapping>
</EntitySetMapping>

Answer 1

I would check these things

1. Make sure the [Key] on the testTabs class is being set

2. Make sure you don't have two different instances of ABEntities2 (DbContext) at the same time

Answer 2

looks like the only problem is usage of sequence , since I changed table definition to

CREATE TABLE [dbo].[testTab]
(
    [iden] [bigint] identity(1,1) NOT NULL ,
    [name1] [nchar](10) NULL,
    [name2] [nchar](10) NULL,
    PRIMARY KEY CLUSTERED 
    (
    [iden] ASC
    )
) ON [PRIMARY]

• so I used identity instead of sequence and recreated model, everything works fine. sequence introduced in sql2012 seems not working with EF6 correctly.