Using LDAP in WPF to find specific user in an Active Directory

Question

In WPF and therefore in the C# programming language, I am trying to use LDAP to find a specific user within an Active Directory. I was able to check if a specific user exists in an Active Directory but I was not able to retrieve that user from the directory in order to gain access to their properties.

I am using the System.DirectoryServices namespace.

Is there a way to do what I seek to achieve, is there a way to retrieve a specific user from the AD using LDAP in order to check their properties?

EDIT: code I used to check if user is in AD. Returns true if user is in AD, false if user is not found. I wonder thought if there is a limit to the number of users it will search.

bool ContainsUser(string domain, string userName)
        {
            string ldapBase = string.Format("LDAP://{0}", domain);

            using (var entry = new DirectoryEntry(ldapBase))
            {
                using (var searcher = new DirectorySearcher(entry))
                {
                    searcher.Filter = string.Format("(sAMAccountName={0})", userName);
                    return searcher.FindOne() != null;
                }
            }
        }

Answer 1

You should investigate using UserPrincipal.FindByIdentity

for example:

    public static string GetEmailAddressFromActiveDirectoryUserName(string adUserName)
    {
        string email = string.Empty;
        if (!string.IsNullOrEmpty(adUserName))
        {
            using (var pctx = new PrincipalContext(ContextType.Domain))
            {
                using (UserPrincipal up = UserPrincipal.FindByIdentity(pctx, adUserName))
                {
                    return !string.IsNullOrEmpty(up?.EmailAddress) ? up.EmailAddress : string.Empty;
                }
            }
        }
        return email;
    }

See:

https://docs.microsoft.com/en-us/dotnet/api/system.directoryservices.accountmanagement.userprincipal.findbyidentity?view=netframework-4.8

Answer 2

The code you use to check that the user exists in AD or not already loads user properties: searcher.FindOne()?.Properties .

public class User
{
    public string UserPrincipalName { get; set; }
    public string Name { get; set; }
}

User GetAdUser(string domain, string userName)
{
    string ldapBase = string.Format("LDAP://{0}", domain);

    using (var entry = new DirectoryEntry(ldapBase))
    {
        using (var searcher = new DirectorySearcher(entry))
        {
            searcher.Filter = string.Format("(sAMAccountName={0})", userName);
            var result = searcher.FindOne();
            User user = null;
            if (result != null)
            {
                // result.Properties - list of loaded user properties
                // result.Properties.PropertyNames - list of user property names                
                user = new User
                {
                    UserPrincipalName = result.Properties["userprincipalname"].Cast<string>().FirstOrDefault();
                    Name = result.Properties["name"].Cast<string>().FirstOrDefault();
                }
            }

            return user;
        }
    }
}