Determine current domain controller programmatically

Question

I need to query current domain controller, probably primary to change user password.

(P)DC name should be fully qualified, i.e. DC=pdc,DC=example,DC=com (how to properly name such notation?)

How can it be done using C#?

Answer 1

To retrieve the information when the DomainController exists in a Domain in which your machine doesn't belong, you need something more.

  DirectoryContext domainContext =  new DirectoryContext(DirectoryContextType.Domain, "targetDomainName", "validUserInDomain", "validUserPassword");

  var domain = System.DirectoryServices.ActiveDirectory.Domain.GetDomain(domainContext);
  var controller = domain.FindDomainController();

Answer 2

We are using something like this for our internal applications.

Should return something like DC=d,DC=r,DC=ABC,DC=com

public static string RetrieveRootDseDefaultNamingContext()
{
    String RootDsePath = "LDAP://RootDSE";
    const string DefaultNamingContextPropertyName = "defaultNamingContext";

    DirectoryEntry rootDse = new DirectoryEntry(RootDsePath)
    {
        AuthenticationType = AuthenticationTypes.Secure;
    };
    object propertyValue = rootDse.Properties[DefaultNamingContextPropertyName].Value;

    return propertyValue != null ? propertyValue.ToString() : null;
}