Database Won't Update Using Savechanges Method on Entity - entity-framework

Question

I am using the Entity Framework in a MVC Web API and I can't figure out why the changes aren't being saved to the database. I am using the following code:
[HttpPost]
public HttpResponseMessage PostPXE(PXE pxe)
{
var pxeRequestID =
from qsp in db.Queue_Server_Provision
.Where(a => a.Server_Name == pxe.Server_Name)
join isni in db.IaaS_Server_NIC_Information
.Where(a => a.MAC == pxe.Mac_Address)
on qsp.IaaS_ID equals isni.IaaS_Server_Information_IaaS_ID
select qsp.Request_ID;
var QSP = db.Queue_Server_Provision.Find(pxeRequestID.FirstOrDefault());
db.Queue_Server_Provision.Attach(QSP);
QSP.Provision_Status_Code = "240.9";
db.Entry(QSP).State = EntityState.Modified;
try
{
db.SaveChanges();
}
catch (DbUpdateConcurrencyException e)
{
return Request.CreateResponse(HttpStatusCode.NotFound, e.Message);
}
catch (Exception e)
{
return Request.CreateResponse(HttpStatusCode.NotFound, "error");
}
return Request.CreateResponse(HttpStatusCode.OK);
}
While debugging everything seems to work fine until I call the SaveChanges() method, at that point the Provision_Status_Code value reverts to what it was before being modified.
The following SQL is generated from the Entity Framework:
exec sp_executesql
N'update [dbo].[Queue_Server_Provision]
set [Server_Name] = #0,
[Environment_List_ID] = #1,
[Operating_System_List_ID] = #2,
[Container_Size_List_ID] = #3,
[Active_Directory_List_ID] = #4
where ([Request_ID] = #5)
select [IaaS_ID],
[Provision_Status_Code],
[Provision_Status_Text],
[Provision_Phase],
[Last_Update_Time],
[Canceled]
from [dbo].[Queue_Server_Provision]
where ##ROWCOUNT > 0 and [Request_ID] = 5',
N'#0 nvarchar(16),
#1 uniqueidentifier,
#2 uniqueidentifier,
#3 uniqueidentifier,
#4 uniqueidentifier,
#5 uniqueidentifier',
#0=N'IaaSTest222',
#1='31097372-E4A6-461D-AFCC-BFAF069A6710',
#2='CF44FE08-56DE-4A7D-813A-08A7AD215E8B',
#3='15AEB74F-E0CB-4219-AC69-8C623DE8DF46',
#4='EA08BB7E-5C1F-4F6B-83D6-4BF9F6C55FF7',
#5='34CA5F9C-2BF8-40E5-8BDD-5DE7364C18C3'

Answer 1

This looks very much like Entity Framework "thinks" that the Provision_Status_Text column is generated in the database - either because it's an identity (unlikely for a string column) or because it's a computed column.
Indication for this is:
The column is not part of the set expression in the update statement although you changed that column. If the column is database generated this is expected.
The column is returned in the sql select expression. For a database generated column this is expected again because EF wants to update the entity on client side with the current computed database values after an insert or update.
The same applies by the way for the other columns that occur in the select statement.
If you are using Code-First workflow check if those properties are annotated with one of the
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
attributes or if
....HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)
....HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed)
is used with Fluent API.
If you are using Database-First or Model-First workflow with EDMX check your EDMX file for StoreGeneratedPattern="Identity" or StoreGeneratedPattern="Computed" attributes. You should find these settings in the designer surface as well.
It does not necessarily mean that the column is really generated in the database. But if one of these settings is in the model metadata EF will assume it is and behave the way you see it. It could mean that database and model are "out of sync" for some reason because some manual changes have been done in the database schema or the model perhaps without updating the other side.