try
{
    // Bind to the users container.
    DirectoryEntry entry = new DirectoryEntry("LDAP://CN=users,DC=fabrikam,DC=com");
    // 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);
}