See if user is part of Active Directory group in C# + Asp.net

Question

I need a way to see if a user is part of an active directory group from my .Net 3.5 asp.net c# application.

I am using the standard ldap authentication example off o

Answer 1

How to check user is in AD member and specific AD group member

//This Reference and DLL must be attach in your project         
//using System.DirectoryServices.AccountManagement;        


         public bool IsAuthenticated(string username, string pwd)
        {

            using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, "xxx.com"))   // Your Domain Name
            {
                if (pc.ValidateCredentials(username, password))  //User and Password is OK for Active Directory 
                {
                    UserPrincipal user = UserPrincipal.FindByIdentity(pc, username);  //Get User Active Directory Information Details
                    if (user != null)
                    {

                        var groups = user.GetAuthorizationGroups();   // Get User Authorized Active Directory Groups
                        foreach (GroupPrincipal group in groups)
                        {
                            if (group.Name.Equals("SpecificActiveDirectoryGroupName"))  //Check if user specific group members
                            { 
                                return true;
                            }

                        }
                    }
                }
            }
            return false;
        }