sql server 2005 - SqlDependency throwing Invalid Operation exception -

In our project, we are invalidating the cache based on the change in query output. This change is implemented using notifications.

In the file block in Global.asax we also have SqlDependency.Start (has been added) ConnectionStr) . However, the following invalid operation is throwing exceptions:

Message "When using SqlDependency without providing an option value, SqlDependency.Start () is said to be executed before the execution of an order SqlDependency Frequency. "String

What could be the possible cause of this problem?