Connection pool connections consumed when in TransactionScope - sql-server-2008

Question

Can someone explain why we are experiencing a total consumption of the connection pool when performing queries inside TransactionScope resulting in
System.InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
I have reduced our problem to the following:
SomeNonTransactionalCode()
{
// This code will execute with just one connection to the database
// and complete without exception
List<BusinessEntity> beList;
for (int i = 0; i < 101; i++)
{
BusinessEntityRepository beRepo = new BusinessEntityRepository();
beList = beRepo.ReadAll().ToList();
}
}
SomeTransactionalCode()
{
// This code will cause the connections to the database to increment
// with every iteration eventually timing out after 100 connections
using (TransactionScope transactionScope = new TransactionScope())
{
List<BusinessEntity> beList;
for (int i = 0; i < 101; i++)
{
BusinessEntityRepository beRepo = new BusinessEntityRepository();
beList = beRepo.ReadAll().ToList();
}
transactionScope.Complete();
}
}
EDIT
After Omer's answer below I think the problem is explained better like this:
SomeNonTransactionalCode()
{
// This code will execute with just one connection to the database
List<BusinessEntity1> be1List;
BusinessEntity1Repository be1Repo = new BusinessEntity1Repository();
be1List = be1Repo .ReadAll().ToList();
List<BusinessEntity2> be2List;
BusinessEntity2Repository be2Repo = new BusinessEntity2Repository();
be2List = be2Repo .ReadAll().ToList();
List<BusinessEntity3> be3List;
BusinessEntity3Repository be3Repo = new BusinessEntity3Repository();
be3List = be3Repo.ReadAll().ToList();
}
SomeTransactionalCode()
{
// This code will cause three seperate connections to the database
using (TransactionScope transactionScope = new TransactionScope())
{
// note this is simplified - the code below could be in unknown nested
// methods make creating of the repos prior to calling not possible
List<BusinessEntity1> be1List;
BusinessEntity1Repository beRepo1 = new BusinessEntity1Repository();
be1List = be1Repo.ReadAll().ToList();
List<BusinessEntity2> be2List;
BusinessEntity2Repository beRepo2 = new BusinessEntity2Repository();
be2List = be2Repo.ReadAll().ToList();
List<BusinessEntity3> be3List;
BusinessEntity3Repository beRepo3 = new BusinessEntity3Repository();
be3List = be3Repo.ReadAll().ToList();
transactionScope.Complete();
}
}
Surely this is not expected behaviour? I have read nothing that explains why this might be happening. I can only assume it is something to do with how we have implemented our repositories. Hopefully the following will give a good enough description of the implementation.
public class BusinessEntityRepository
{
private BusinessEntityDal Dal { get; set; }
public BusinessEntityRepository()
{
this.Dal = new BusinessEntityDal ();
}
public IQueryable<BusinessEntity> ReadAll()
{
IQueryable<BusinessEntity> query = null;
if (Dal != null)
{
query = Dal.ReadAll();
}
//-Return
return query;
}
}
public class BusinessEntityDal : BaseDal
{
public IQueryable<BusinessEntity> ReadAll()
{
var result = from de in this.DC.BusinessEntityTable
select new BusinessEntity
{
Property1 = Column1,
Property2 = Column2,
// etc...
};
//-Return
return (result);
}
}
public abstract class BaseDal
{
protected OurDataContext DC;
public BaseDal()
{
// create a DataContext
this.DC = new OurDataContext();
}
}
public class OurDataContext : System.Data.Linq.DataContext
{
private static readonly string _cn = // some static connection string taken from web.config
public OurDataContext()
: base(OurDataContext._cn)
{
}
}
Our connection string is fairly conventional and leaves the number of connections in the pool at the default 100 (hence the 101 iterations to test the issue in my code above).

Answer 1

You are creating new DataContext references inside the for loop.
for (int i = 0; i < 101; i++)
{
BusinessEntityRepository beRepo = new BusinessEntityRepository();
beList = beRepo.ReadAll().ToList();
}
It is keeping all those in different transactions. If you just put repo init code outside the for loop and perform all operations in one context, it will be fine.
using (TransactionScope transactionScope = new TransactionScope())
{
List<BusinessEntity> beList;
BusinessEntityRepository beRepo = new BusinessEntityRepository();
for (int i = 0; i < 101; i++)
{
beList = beRepo.ReadAll().ToList();
}
//do some other things with same context
transactionScope.Complete();
}