if you get the error message
DataPortal.Fetch failed
There is already an open DataReader associated with this Command which must be closed first.
this isn't a Csla problem. It's MARS related.
MARS = Multiple Active Record Sets and means exactly what it says: you can have more than one DataReader on a single connection. MARS isn't supported on every SQL database (for instance SQL2000 doesn't support it) and you must enavle it in the connection string (or equivalent).
I was using
protected void DataPortal_Fetch()
{
using (SqlConnection cn = new SqlConnection(Database.DocStoreConnection))
{
using (SqlCommand cmd = new SqlCommand("GetDocStatusNVL", cn))
{
cmd.CommandType = CommandType.StoredProcedure;
cn.Open();
...
and in order to take advantage of the ConnectionManager feature, changed it to
protected void DataPortal_Fetch()
{
using (var ctx = ConnectionManager<SqlConnection>.GetManagerDatabase.DocStoreConnection, false))
{
using (SqlCommand cmd = new SqlCommand("GetDocClassNVL", ctx.Connection))
{
cmd.CommandType = CommandType.StoredProcedure;
...
The difference is that on the later case, I'm reusing the connection (that's the purpose of ConnectionManager). Another difference is that I got the above error message. 
It looks like I'm in the middle of some other DataPortal operation and didn't close the DataReader. In fact I'm fetching a big read only list and converting the DocClass IDs to DocClass names. This is done on a row by row base. That's not a problem as the NVL is cached and the fecth only hits the database on the first call.
SOLUTION - Go back to the first form.
Copyright (c) Marimer LLC