How to succesfully connect with DirectoryEntry in C# to a localhost LDAP domain?

I'm running Ubuntu on Windows via WSL in a CLI, and I've configured LDAP (OpenLDAP: slapd) on Ubuntu as follows:

BASE    dc=example,dc=com
URI     ldap://localhost

When I run on the following command on Ubuntu, it shows me the structure of the Users and Groups I've set on the LDAP server, which indicates that I'm able to connect with the server using my test user:

ldapsearch -D "cn=test,ou=Department,dc=example,dc=com" -w test -b 'dc=example,dc=com' '(objectclass=*)'

On my Windows host machine, I checked the box for Active Directory Lightweight Directory Services in the Turn Windows features on or off window, which enables usage of LDP.exe. In LDP.exe, I'm also able to connect with the LDAP server, by selecting Connection > Bind > filling in "cn=test,ou=Department,dc=example,dc=com" for the User field and "test" for the Password field > and selecting Simple bind before clicking OK:

After clicking OK, LDP.exe provides the following feedback:

I'm also able to retrieve information from the LDAP server in my C# code—for example:

de = new DirectoryEntry("LDAP://localhost:389/ou=Department,dc=example,dc=com");
de.AuthenticationType = AuthenticationTypes.None;
var childNames = new List<string>();
foreach(DirectoryEntry child in de.Children)
{
    childNames.Add(child.Name.ToString());
}

The above gives me the confidence that the LDAP server is configured correctly and that I'm able to access it in my code, but I'm unable to connect via the aforementioned test user when I modify the code as follows:

var de = new DirectoryEntry("LDAP://localhost/OU=Department,DC=example,DC=com", username, password);
var childNames = new List<string>();
foreach(DirectoryEntry child in de.Children)
{
    childNames.Add(child.Name.ToString());
}

When I run the above code, I get an error at the foreach part that says that "the user name or password is incorrect."

I've tried to set the username & password variables to all the ways I could think of or find online, such as setting the password to "test" or its SSHA hash, and setting username to "test", "cn=test", "example.com\\test", or "test@example.com", but I keep getting the message that "the user name or password is incorrect" when I run the code.

I've also tried the username & password combinations with several forms of authentication, as such:

var de = new DirectoryEntry("LDAP://localhost/OU=Department,DC=example,DC=com", username, password, AuthenticationTypes.Secure);

But I've been unable to find the correct configuration. How do I configure the code so that the username and password combination is accepted?

You said:

> I'm running Ubuntu on Windows via WSL in a CLI, and I've configured LDAP (OpenLDAP: slapd) on Ubuntu

And then:

> On my Windows host machine, I checked the box for Active Directory Lightweight Directory Services in the Turn Windows features on or off window

That means you now have two LDAP servers running on the same machine. I'm guessing that the AD LDS instance is taking precedence, and that's the instance that's giving you the "user name or password is incorrect" error.

If you want to connect to your OpenLDAP instance, you'll need to disable Active Directory Lightweight Directory Services. If you want to keep LDP, you can copy the ldp.exe file out of the Windows\System32 folder before you uninstall AD LDS, then copy it back after.

Apparently, the username must contain the full DN. The code below works:

string username = "cn=test,ou=Department,dc=example,dc=com", password = "test";
var de = new DirectoryEntry("LDAP://localhost:389/ou=Department,dc=example,dc=com", username, password, AuthenticationTypes.None);
childNames = new List<string>();
foreach(DirectoryEntry child in de.Children)
{
    childNames.Add(child.Name.ToString());
}

On the Microsoft pages, it's said that AuthenticationTypes.None "equates to zero, which means to use basic authentication (simple bind) in the LDAP provider." I first assumed that AuthenticationTypes.None means that the username and password won't be checked for correctness (as with AuthenticationTypes.Anonymous), but that's not the case.