Unknown Error (0x80005000) with LDAPS Connection

I've been stuck for the last couple of hours on an annoying Active Directory bit.

What I'm trying to accomplish is connect to an Active Directory via LDAP over SSL. The authentication type is anonymous. I'm using .NET Framework 4.0, C# and Visual Studio 2010.

The following code should work according to various online resources. But it keeps coming up with the amazing self-explanatory: 'Unknown Error (0x80005000)'.

DirectoryEntry entry = new DirectoryEntry();
entry.Path = "LDAPS://some.ldap.server:636";
entry.AuthenticationType = AuthenticationTypes.SecureSocketsLayer;

DirectorySearcher searcher = new DirectorySearcher();
searcher.searchRoot = entry;
searcher.Filter = "(&(objectCategory=person)(objectClass=user))";

SearchResultCollection results = searcher.FindAll();

I've simplified the actual query I want to perform to the one you find in the code. But even with this generic query (it should return work on every AD?) it returns the error.

Finally!

It seems that an ASP.NET application does not have the rights (or doesn't know how) to examine the trusted certificate store at machine level. Since the certificate was self-signed the ASP.NET application refused to establish a connection.

I fixed the problem using custom certificate validation. The following code did the trick:

LdapConnection con = new LdapConnection(new LdapDirectoryIdentifier("server", port));
con.SessionOptions.SecureSocketLayer = true;
con.SessionOptions.VerifyServerCertificate = new VerifyServerCertificateCallback(ServerCallback);
con.Credential = new NetworkCredential(String.Empty, String.Empty);
con.AuthType = AuthType.Basic;
con.Bind();

Since I am sure the certificate is valid, the ServerCallBack method looks like this:

public static bool ServerCallBack(LdapConnection connection, X509Certificate certificate)
{
    return true;
}

But you can always of course retrieve the certificate from the local machine and validate it.

The namespace used in this example is:

System.DirectoryServices.Protocols;

This is because the namespace:

System.DirectoryServices.DirectoryEntry

does not contain a method for custom certificate validation.

Thank you all for your help and time, and hopefully this will help someone in the future!