See the code below. If I initialize more than one entity context, then I get the following exception on the 2nd set of code only. If I comment out the second set it works.
{"The underlying provider failed on Open."}
Inner: {"Communication with the underlying transaction manager has failed."}
Inner: {"Error HRESULT E_FAIL has been returned from a call to a COM component."}
Note that this is a sample app and I know it doesn't make sense to create 2 contexts in a row. However, the production code does have reason to create multiple contexts in the same TransactionScope, and this cannot be changed.
Edit
Here is a previous question of me trying to set up MS-DTC. It seems to be enabled on both the server and the client. I'm not sure if it is set up correctly. Also note that one of the reasons I am trying to do this, is that existing code within the TransactionScope uses ADO.NET and Linq 2 Sql... I would like those to use the same transaction also. (That probably sounds crazy, but I need to make it work if possible).
http://stackoverflow.com/questions/794364/how-do-i-use-transactionscope-in-c
Solution
Windows Firewall was blocking the connections to MS-DTC.
using(TransactionScope ts = new System.Transactions.TransactionScope())
{
using (DatabaseEntityModel o = new DatabaseEntityModel())
{
var v = (from s in o.Advertiser select s).First();
v.AcceptableLength = 1;
o.SaveChanges();
}
//-> By commenting out this section, it works
using (DatabaseEntityModel o = new DatabaseEntityModel())
{
//Exception on this next line
var v = (from s1 in o.Advertiser select s1).First(); v.AcceptableLength = 1;
o.SaveChanges();
}
//->
ts.Complete();
}