Using C# to Access a Network Directory

Using C# to Access a Network Directory

The main .NET class for working with network directory services objects is the DirectoryEntry class, found in the System.DirectoryServices namespace. The DirectoryEntry class allows you to bind to a directory object and perform operations to retrieve, add, delete, and modify information about the object.

The DirectoryEntry class has many constructor formats, depending on your requirements within the database.

Anonymous Directory Login

Many network directory services allow either all or some database objects to be read by anyone on the network, regardless of network permissions. This allows network users to look up resources on the network, such as a user phone number and address, without requiring advanced privileges on the directory server.

To create a DirectoryEntry instance to reference a directory object without using privileges, you use the following constructor format:

DirectyoryEntry(string ldappath)

The ldappath parameter is a string value that represents the location of the database object. The object must be referenced using a URI-like syntax, which includes the access method, the network directory service server address, and the distinguished name of the object.

The ADSI library offers various access methods for connecting to different types of network directory services. Each access method is specified in a URI format. Figure lists the access methods available to use.

For AD access, you should use the LDAP access method because it offers the most robust access method, including searching capabilities (described in the “Searching the Network Directory” section).

After the access method, the address of the desired directory server should be specified, along with the full distinguished name of the object to reference. A few examples of proper LDAP paths would be:

LDAP://server1.ispnet1.net/dc=ispnet1, dc=net
LDAP://server1.ispnet1.net/cn=kblum, ou=sales, dc=ispnet1, dc=net
LDAP://192.168.1.100/ou=accounting, dc=ispnet1, dc=net

Listing 15.1 shows the BindObject.cs program, which binds a variable to a directory object and displays the LDAP path associated with the object.

Listing 15.1: The BindObject.cs program

using System;
using System.DirectoryServices;
class BindObject
{
  public static void Main()
  {
   DirectoryEntry de = new DirectoryEntry(
     "LDAP://192.168.1.100/dc=ispnet1, dc=net");
   string ldappath = de.Path;
   Console.WriteLine("The LDAP path is: {0}", ldappath);
   de.Close();
  }
}

While the BindObject program is extremely trivial (seeing as you need to know the LDAP path to bind to the object anyway) it shows the basic steps required to bind a variable to a directory services object. The Path property retrieves the LDAP path of the object as a string value, which can be used in a DirectoryEntry instance to bind to the object. This will be used later in the "Searching the Network Directory" section to iterate through objects in a directory service.

The output from this example is simple. If you were successful in binding to the directory service object, the LDAP path should display on the console. This entry should be the same as what you used to create the DirectoryEntry object. If the program was not able to bind to the directory services object, an Exception will be thrown, stating the reason for the error. One of the most common errors is that the directory services server requires that you authenticate yourself before binding to an object.

Logging In to a Directory

For database actions that require user authentication, two formats can be used. The following constructor allows you to specify a username and password to use to login into the directory service:

DirectoryEntry(string ldappath, string username, string password)

Once the connection is authenticated, you can perform the actions that the username specified is allowed to perform, including adding, deleting, or modifying objects.

The second constructor allows you to specify a specific authentication type used for the login:

DirectoryEntry(string ldappath, string username, string password,
    AuthenticationTypes authtype)

The AuthenticationTypes enumerator specifies the authentication type used for logging into the directory service server.

Figure shows the authentication types that are available.

An example of using authentication to access a directory object is:

DirectoryEntry de = DirectoryEntry("LDAP://192.168.1.100/dc=ispnet1, dc=net",
  "rich", "password", AuthenticationTypes.ServerBind);

This example uses the server username “rich” and the appropriate password to log into the directory services server.