Communicate with Active Directory via LDAP

Having written a natty local authentication system for an application I wanted to expand it further by authenticating users against a domain too, as an option. 

I have a test domain controller on another machine, but my development machine is not joined to that domain. 

Reading a few stack overflow posts it seemed the best method of communicating with AD is via System.DirectoryServices.AccountManagement . This under the hood uses the older, domain communicate API but makes it all a little bit more accessible to idiots newbies like me. 

It's relatively simple:

Set-up your context

var ctx = 
new PrincipalContext(ContextType.Domain, "server", "DC=doom,DC=home", 
ContextOptions.SimpleBind, username,password);

I discovered 'ContextOptions' very important in my testing as the default bind option didn't work for me. 

Validate your credentials

var validCredentials = 
ctx.ValidateCredentials(username, password, ContextOptions.SimpleBind);

This is how I determine if the user has passed me valid credentials

Pull out the user details from the AD

var user = UserPrincipal.FindByIdentity(ctx, IdentityType.SamAccountName, username);

However, the above will not work if your development machine is not joined to the domain. The workaround is to open up your network settings and use the domain server as your only DNS server, otherwise your application will not be able to locate the domain and associated services to complete the request. 




Finally, you're really going to want to put all this on a separate thread. LDAP queries take an age!