.NET 4.0 Entity framework Error on Insert?

I don't know why it's is error on SaveChanges(), i search in google, some body say using EF, the database's table such have primary key, i have this, but still error. The error messa开发者_如何学JAVAge is not enough clear,it just throws System.Data.UpdateException. The Code:

public static void AddAccount(int _acc_id,string _name)
{
    dataEntities de = new dataEntities(GetEntityConn());
    account acc = new account
    {
        account_id = _acc_id,
        name =  _name
    };
    de.AddObject("account", acc);
    de.SaveChanges();
}

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Solved : I found the solution, see this thread : http://social.msdn.microsoft.com/Forums/en-US/sqlce/thread/48984bd4-0921-4637-bd8f-8aa1ae9514ab For short, don't use int as datatype , use uniqueidentifier type.This problem will not happen on SQL Server, it only occur when using SQLCE.

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My psychic powers tell me that the account_id field has a unique constraint on it and that the value of _acc_id is already in the table.

If my mighty psychic powers are wrong, then more information is required. 8 )

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Guessing that the EntitySetName isn't called account, but that's hard to tell without more information.

What I would do is something like:

public static void AddAccount(int _acc_id,string _name)
{
    dataEntities de = new dataEntities(GetEntityConn());
    account acc = new account
    {
        account_id = _acc_id,
        name =  _name
    };
    de.Accounts.Add(acc);
    de.SaveChanges();
}

This gets rid of the string value, so it should also help refactoring

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Update: I have tried create a same table on SQL Server 2008, generate edmx file from that, and use same code for insertion,it works! So i believe it all about EF 4.0 with SQLCE.... I upload a test project in window form , with a SQLCE database , and with one button event, you can download on

http://www.netfrd.com/testproject.zip

The code is very simple ,but it really not work.