Delete all files from folder or Directory in ASP.Net C#

Sir,

I want delete all the datas in server side folder 'documents' when the page load.

I am using following code

string filePath = Server.MapPath("documents");                        System.IO.File.Delete(filePath);  

when i run the following error occur.

Access to the path 'D:\Library\documents' is denied.

How to delete server side folder either it has data or not?