How to identify the protected wmv/asf file?

How to identify the protected wmv/asf file ?

IWMReader ->Open( File)

if the wmv or asf file is not able to open the file,
it will returns error code as license required.
After this one, we can use the IWMDRMReader to query the license details.

Sample program available in Windows media Format SDK samples :

DRMShow.exe - i "DRMShow.wmv" // DRMShow.wmv is available in directX media dir path