We are migrating MVC application from Extjs3 to Extjs4
Below are the steps we followed.
1) Added
Ext JS 3 Compatibility Layer
2)Added ext3-compat.js and ext3-core.compat.js files reference
3) Added Extjs4 reference
4) Removed the Extjs3 reference

5)Changed Ext3 grid(with paging toolbar) to Ext4
This results in the below output:

An Empty screen --The UI cannot be seen.
Exceptions thrown are :

1."Ext is not defined" in ext3-compat.js at
if (Ext.toolbar && Ext.toolbar.Toolbar)

2."Ext is not defined" in ext3-core-compat.js at
Ext.Compat = function() in ext3-core-compat.js

Could you please help to resolve this