Error opening site when adding AD users to SharePoint Group

Question

I am working on Sharepoint and I am trying to save all the users from Active Directory into the Sharepoint under same group. If I run my code then I get this error:

The Web application at http://localhost/ could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.

string groupname = txtgroupname.Text;
Uri sitePath = new Uri(@"http://localhost");
List<ADUserDetail> users = new List<ADUserDetail>();
users = BuildList(users, "LDAP://server-abc/dc=abc,dc=bb,dc=ca", groupname);
foreach (var adUser in users)
{
 using (SPSite spSite = new SPSite(sitePath.ToString()))
 {
  using (SPWeb spWeb = spSite.OpenWeb())
  {
    spWeb.AllowUnsafeUpdates = true;
    SPUser spUser = spWeb.EnsureUser(adUser.Samaccountname);
    if (spUser != null)
    {
     SPGroup spGroup = spWeb.SiteGroups[groupname];
     if (spGroup != null)
      spGroup.AddUser(spUser);
    }
   }
  }
 }

Dot Net version 4

Server is 64 bit (Any CPU)

Answer 1

Make sure that you are running your code from the server as an administrator. Also replace Localhost with the actual Web Application URL.