FIX | db_id returns null on Azure SQL Database. (#1294)

* db_id() issue.

* closed reader.

* commit

* review comments

Co-authored-by: David Engel <dengel1012@gmail.com>

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlDependencyListener.cs

@@ -106,6 +106,7 @@ internal SqlConnectionContainer(SqlConnectionContainerHashHelper hashHelper, str
                 _con.Open();
 
                 _cachedServer = _con.DataSource;
+                bool? dbId = null;
 
 #if NETFRAMEWORK
                 if (hashHelper.Identity != null)
@@ -125,7 +126,16 @@ internal SqlConnectionContainer(SqlConnectionContainerHashHelper hashHelper, str
                     CommandText = "select is_broker_enabled from sys.databases where database_id=db_id()"
                 };
 
-                if (!(bool)_com.ExecuteScalar())
+                // db_id() returns the database ID of the current database hence it will always be one line result
+                using (SqlDataReader reader = _com.ExecuteReader(CommandBehavior.SingleRow))
+                {
+                    if (reader.Read() && reader[0] is not null)
+                    {
+                        dbId = reader.GetBoolean(0);
+                    }
+                }
+
+                if (dbId is null || !dbId.Value)
                 {
                     throw SQL.SqlDependencyDatabaseBrokerDisabled();
                 }