connect anonymous to ldap server in .net

"The following code examples show how to search for all users in a domain. It contains some basic required tasks such as using a C# try-catch or Visual Basic .NET try-catch-finally statement to catch errors and error handling for all the errors that can be thrown by the DirectorySearcher object."

http://msdn.microsoft.com/en-us/library/ms180885(v=vs.80).aspx[^]

try
{
    string username =@"your username"
    string password =@"your password"
    // Bind to the users container.
    DirectoryEntry entry = new DirectoryEntry("LDAP://CN=users,DC=fabrikam,DC=com",username,password);
    // Create a DirectorySearcher object.
    DirectorySearcher mySearcher = new DirectorySearcher(entry);
    // Create a SearchResultCollection object to hold a collection of SearchResults
    // returned by the FindAll method.
    SearchResultCollection result = mySearcher.FindAll();
    // Get search results. For more information, see Getting Search Results.
    // ...
    // This sample uses Try...Catch to catch errors.
    // Create an Exception object. For more information, see System.Exception.
}
catch (System.Runtime.InteropServices.COMException)
{
    System.Runtime.InteropServices.COMException exception = new System.Runtime.InteropServices.COMException();
    Console.WriteLine(exception);
}
catch (InvalidOperationException)
{
    InvalidOperationException InvOpEx = new InvalidOperationException();
    Console.WriteLine(InvOpEx.Message);
}
catch (NotSupportedException)
{
    NotSupportedException NotSuppEx = new NotSupportedException();
    Console.WriteLine(NotSuppEx.Message);
}