It depends Current Url of your
IFrame
is of the same Domain or not.
If the set Url is of the same Domain then you may try below code to get it.
var currentUrl = document.getElementById("MyIframeId").contentWindow.location.href;
But in case if it is set to some other Domain Url, For Example - "http://www.codeProject.com", then I doubt you will be able to get it.