Same domain
If both the pages are in same domain, then you can easily communicate from child with parent page by
window.parent
.
You can call a function of parent page by
window.parent.someFunction(argument1, argument2);
.
You can pass any number of arguments according to the function signature in parent page.
So, after the update in
WebForm1.aspx
page, just call the parent function as said above and update the Grid.
Different domain
If both parent and child are in different domain, then you have to use
window.postMessge
technique for communication. For that check my tip -
Communication with Cross Domain IFrame - A Cross Browser Solution[
^].