Question: How can i use the server.mappath method in a C# class library class ,which acts as my BusinessLayer for My ASP.NET WEbsite

Answer: 
You should reference System.Web and call:

```
  HttpContext.Current.Server.MapPath(...)

```
```
HostingEnvironment.MapPath
System.Web.Hosting.HostingEnvironment.MapPath(path);

```