vb.net - VB net and postgres : Getting "An operation is already in progress" using npgsql -

i'm using following code retrieve list of objects (products) , list (sizes) inside of them.

dim l new list(of entidades.producto)  dim c new npgsqlcommand("select id, name product", cn) dim r npgsqldatareader = c.executereader  while r.read      dim p new entidades.product     p.id = r.item("id")     p.name = r.item("name")     l.add(p)      >>> had other loop here having same issue tried put     reader outside of loop.  loop  r.close()  each p in l     c = new npgsqlcommand("select t.id id, t.name nombre productsize pt join size t on t.id = pt.sizeid productid = :productid order ord", cn)     c.parameters.addwithvalue("productid", pgsqltypes.npgsqldbtype.integer, p.id)     c.prepare() <---- here error      dim rt npgsqldatareader = c.executereader      while rt.read          dim t new size         t.id = rt.item("id")         t.nombre = rt.item("name")         p.size.add(t)      loop  next   return l 

and i'm getting "an operation in progress" error when execute prepare.

i thought closing reader enough run another.

anyone had same problem?

thanks advance

actually, found problem. second loop not closing reader, , when called function again, exploded.

thanks steve tip.