C# Magento API - Get a list of the child products belonging to a bundled product?

U开发者_如何学运维sing the Magento API is it possible to find what simple products are the child products of a bundled product?

I have tried this but catalogProductLinkList returns 0 results:

MagentoService _magento = new MagentoService();
string sessionId = _magento.login(user, key);
catalogProductLinkEntity[] relatedProducts = _magento.catalogProductLinkList(sessionId, "grouped", "sku_of_bundle", null);
if (relatedProducts != null && relatedProducts.Count() > 0)
{
    // do something
}