'Help' The primary key column cannot be generated by the server
<p>My create table code like :</p>

<pre><code>CREATE TABLE [dbo].[DeTai](
[ID] [int] IDENTITY(1,1) NOT NULL,
[MaDeTai]  AS ('DT'+right('000000'+CONVERT([varchar](10),[ID]),(6))) PERSISTED NOT NULL,
[TenDeTai] [nvarchar](255) NOT NULL,
[LinhVuc] [nvarchar](255) NOT NULL,
[Nam] [int] NOT NULL,
[MaGV] [varchar](8) NOT NULL,
)
</code></pre>

<p>When I use linq to sql to insert a values this messages come out </p>

<blockquote>
  <p>The primary key column of type <code>'VarChar(8)'</code> cannot be generated by the server.</p>
</blockquote>

<p>what should i do ?</p>