"Позвоните" USE SomeOtherDB "(например, Master), чтобы закрыть собственное соединение, или один из"
//on master ... CREATE
using (var cnn = new SqlConnection(MASTER))
{
cnn.Open();
var createDbCmd = new SqlCommand(string.Format("create database [{0}]", db), cnn).ExecuteNonQuery();
cnn.Close();
}
using (var cnn = new SqlConnection(tempDB))
{
cnn.Open();
var createTbl = new SqlCommand(string.Format("create table t (t int )"), cnn).ExecuteNonQuery();
var dropTbl = new SqlCommand(string.Format("drop table t"), cnn).ExecuteNonQuery();
//Do additional stuf
var userMaster = new SqlCommand(string.Format("use master"), cnn).ExecuteNonQuery();
cnn.Close();
}
//on master ... CREATE
using (var cnn = new SqlConnection(MASTER))
{
cnn.Open();
var dropDbCmd = new SqlCommand(string.Format("drop database [{0}]", db), cnn).ExecuteNonQuery();
cnn.Close();
}