Issue with Model dialogue window in IE 11

Hello all,

browser : IE 11.
application developed in .Net

issue : In my application I have a model dialogue window which is window.showModalDialog(which is coming as iframe in DOM). I have created recorded a script in chrome and executing it on IE and Chrome(as there is existing issue with script record on IE, recorded in chrome and running it on both browser)

the same script is working fine on Chrome, but gives error with IE.

Error : iframe can not be identified.

can some one help to handle the case with IE.