The best approach to a new dojo.require("esri.dijit.Legend");! Help!

Hello,

What is the best approach to a new dojo.require(""); ? I need to ensure that the module has been loaded. I tried to use the "dojo.addOnLoad" but it did not work. I tried to include the "index.html" and also does not work. How can I ensure this in the code? The current code:

dojo.require("esri.dijit.Legend");

dojo.declare("Edit.UI.Web.CarteInteractive.SimpleLayerLegendListView", geocortex.framework.ui.ViewBase, {

...

}

Thanks!