Response object throws exceptions

I'm using the Response object to download a file on the client.  In the debugger watches I have for:
SubStatusCode 'Response.SubStatusCode' threw an exception of type 'System.PlatformNotSupportedException'
 base {"This operation requires IIS integrated pipeline mode."} System.NotSupportedException {System.PlatformNotSupportedException}
Headers 'Response.Headers' threw an exception of type 'System.PlatformNotSupportedException'

The file is actually downloaded.  The problem is getting the exception stops the thread where I want to do some cleanup after.

The code, althought I believe it is a configuration issue because the exceptions exist before the code is executed.

            Response.ClearHeaders();
            Response.ClearContent();
&nbs ...