IIS configuration to authenticate using Active Directory

Question

I created a web system using C# and use a routine to authenticate the user by taking the Active Directory user. However my system is not getting the AD user: it is catching the user from pool of the application. When I run the system locally on my machine the routine works perfectly, but when I move the system to the server this problem happens.

The routine I use is this:

// Cria um contexto principal para definir a busca na base do AD.
PrincipalContext principalContext = new PrincipalContext(ContextType.Domain);

// Cria uma query do Active Directory Domain Services.
DirectorySearcher directorySearcher = new DirectorySearcher(principalContext.ConnectedServer);

// Cria um filtro para a busca com o login do usuário da rede.
directorySearcher.Filter = "(sAMAccountName=" + System.Environment.UserName + ")";

/*
* Cria um elemento da hierarquia do Active Directory.
* Este elemento é retornado durante uma busca através de DirectorySearcher.
*/
SearchResult searchResult = directorySearcher.FindOne();

// Cria um objeto encapsulado da hierarquia de diretório serviços do AD.
DirectoryEntry directoryEntry = searchResult.GetDirectoryEntry();

return directoryEntry.Properties["displayName"][0].ToString();

I’m using OSI 7.0.