Get Name of User from Active Directory

You want name of a user from active directory. Try code like this:

string name ="";
using (var context = new PrincipalContext(ContextType.Domain))
{
    var usr = UserPrincipal.FindByIdentity(context, User.Identity.Name); 
    if (usr != null)
       name = usr.DisplayName;  
}

or this from social.msdn.microsoft.com:

PrincipalContext ctx = new PrincipalContext(ContextType.Domain);
UserPrincipal user = UserPrincipal.Current;
string displayName = user.DisplayName;

or may be it:

System.DirectoryServices.AccountManagement.UserPrincipal.Current.DisplayName;

The System.DirectoryServices.AccountManagement namespace provides uniform access and manipulation of user, computer, and group security principals across the multiple principal stores: Active Directory Domain Services (AD DS), Active Directory Lightweight Directory Services (AD LDS), and Machine SAM (MSAM).

using System.DirectoryServices.AccountManagement;

string fullName = null;
using (PrincipalContext context = new PrincipalContext(ContextType.Domain))
{
    using (UserPrincipal user = UserPrincipal.FindByIdentity(context, User.Identity.Name))
    {
        if (user != null)
        {
            fullName = user.DisplayName;
            lbl_Login.Text = fullName;
        }
    }
}