Authenticating with Active Directory


If you work in a corporate environment, chances are that your Windows machine is connected to a domain based on Active Directory. In today’s article, we’re going to write a very simple program that allows us to verify a user’s credentials for the domain using Active Directory.

In order to try this out, you’re going to need an Active Directory domain. In my case, I installed Windows Server 2008 R2 and followed these instructions to set up a domain, which I called “ranch.local”. You may also be able to connect to your domain at work to save yourself the trouble of setting this up.

Let us now create a new Console Application using either SharpDevelop or Visual Studio. After adding a reference to System.DirectoryServices.AccountManagement, add the following statement near the top of your Program.cs file:

using System.DirectoryServices.AccountManagement;

Next, remove any code in Main() and add a simple prompt for the username and password to authenticate against Active Directory:

// prompt for username
Console.Write("Username: ");
string username = Console.ReadLine();
// prompt for password
Console.Write("Password: ");
string password = Console.ReadLine();

For the authentication part, we can use a simple method described here. After obtaining a reference to the domain using the PrincipalContext class (specifying the domain as a parameter), we simply use the ValidateCredentials() method to perform the authentication. This gives us a boolean value indicating whether the authentication was successful or not.

// authenticate
using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, "RANCH"))
bool authenticated = pc.ValidateCredentials(username, password);
if (authenticated)
Console.WriteLine("Get lost.");

At this point, we need only add a simple statement to wait for user input before letting the application terminate:


Now, we can build our application and test it on the server (or on any machine that is part of the domain). First, let’s try a valid login:

Very good! And now, a user that doesn’t even exist:


Excellent! As you can see, it only takes a couple of lines of code to perform authentication against Active Directory. I hope you found this useful.

Reference: Authenticating with Active Directory from our NCG partner Daniel DAgostino at the Gigi Labs blog.

Daniel D'Agostino

Daniel has been working in software development for several years in different areas including taxation, email, finance, and online betting. He has also been writing for the web since 2002, and nowadays writes mainly about the latest .NET technologies.

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