Questions about "RasterSupport.Unlock" function

I'm using the LeadTools Eval V17. When I follow the tutorials from the documents installed by the software, I find the following funtions:

RasterSupport.Unlock(RasterSupportType.Dicom, " Your Dicom Key");
RasterSupport.Unlock(RasterSupportType.Medical, "Your Medical Key");
RasterSupport.Unlock(RasterSupportType.Medical3d, "Your Medical 3D Key");

What do these mean? If I don't buy a key number, I can't use some functions? But it can work when I follow the tutorials even now I haven't bought a key number.

Since you are using the free evaluation version, you don't need any unlock keys. This means there is no need to use the RasterSupport.Unlock() method, because all LEADTOOLS features are unlocked in the evaluation version. You need to use the unlock keys only when using the full product version of LEADTOOLS SDK.
For more information, please see this page:
http://www.leadtools.com/Help/LEADTOOLS/v17/DH/to/leadtools.topics~leadtools.topics.unlockingspecialleadfeatures.html

Thanks,
Maen Badwan
LEADTOOLS Technical Support

So I can use all the functions provided by LeadTools during the evaluation period. But after that period, many functions can not be used any more and I have to buy the product. Is that right?

Yes, this is correct. When you purchase LEADTOOLS SDK, you might need to unlock some LEADTOOLS features to use LEADTOOLS document, medical or vector functions.
For more information, please contact our sales department at sales@leadtools.com.

Thanks,
Maen Badwan
LEADTOOLS Technical Support