Enity Framework regular error while command executing - entity-framework

Question

I am developing a WPF Applicaton using Entity Framework for data access. As design pattern i use "MVVM" for tier organization, and "Repository" with "UnitOfWork" for data layer organization.
Generic Repository class:
public class EFRepository : IRepository where T : class
{
public IUnitOfWork UnitOfWork { get; set; }
private IObjectSet _objectset;
private IObjectSet ObjectSet
{
get
{
if (_objectset == null)
{
_objectset = UnitOfWork.Context.CreateObjectSet();
}
return _objectset;
}
}
public virtual IQueryable All()
{
return ObjectSet.AsQueryable();
}
...
Unit of work interface:
public interface IUnitOfWork: IDisposable
{
ObjectContext Context { get; set; }
void Save();
bool LazyLoadingEnabled { get; set; }
bool ProxyCreationEnabled { get; set; }
string ConnectionString { get; set; }
}
I build all L2E queries in model layer, like:
this.repository1.All().First(i => i.Field1 == some_value);
Sometimes here is thrown an EntityCommandExecutionException. It happens sometimes, but not regular. There is no rule to make this exception occur.
Exception Detail:
EntityCommandExecutionException:
{"An error occurred while executing the command definition. See the inner exception for details."}
InnerException:
{"Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding."}
StackTrace:
at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
at System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues)
at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator()
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)
at System.Data.Objects.ELinq.ObjectQueryProvider.b__0[TResult](IEnumerable`1 sequence)
at System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult](IEnumerable`1 query, Expression queryRoot)
at System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute[S](Expression expression)
at System.Linq.Queryable.First[TSource](IQueryable`1 source, Expression`1 predicate)
Please, help me to find out the problem, i really don`t know what to do now =(
p.s.:
I tried to provoke this error building and executing L2E queries in simple Console Application. I tried single L2E queries and through 1000-iterations cycles. But nothing caused this exception.
I can post any additional information if needed.
[23.03.2011]
Additional Info:
Entity Framework 4.0
MSSQL Server 2008
this exception can be thrown any time the query take place. It can be l2e query to small table (<200 rows) or large (>500k rows). Also this exception can be caused by Function Import call
when this exception is thrown,
{"Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding."}
it is thrown immediately, but the connection timeout is set to 30 seconds! (i think that is "key feature")
DB Server is situated in LAN, and there is no heavy traffic on DB.
as i have found out, this exception can occur any time no matter what kind of queries or tables are used.
I dont use transaction. This error occur even if i use only select queries.
I think the problem caused by using WPF with EF, because my "EF part" works fine in Console Application.

Answer 1

The ObjectContext has two timeout parameters:
int x = myObjectContext.Connection.ConnectionTimeout;
and
int? x = myObjectContext.CommandTimeout;
Looking at the exception and callstack I don't think that the ConnectionTimeout is the problem (that's the maximum time to try to establish a connection from the client to SQL Server). You could try to set the CommandTimeout to some high value (that's the timeout for queries and commits with SaveChanges; the value null means that the default of the underlying provider will be taken).