Put the ComboBox in a <div style='display:none;'>. After the page loads, run some javascript that changes the display style to "block". Now the COmboBox is visible, but the dropdownbutton is very small. Attempt to pop up the list. It appears as a very small underline.
I have a blog post with pictures, details, and a workaround that is truly a hack:
http://weblogs.asp.net/peterblum/archive/2011/09/14/fixing-combobox-from-ajax-control-toolkit.aspx
Recommendation: Provide a Recalculate() client-side method that we can call when our javascript makes it visible.
Please also see this post which becomes relevant once you fix the visibility problem:
http://weblogs.asp.net/peterblum/archive/2011/09/16/more-with-ajax-control-toolkit-s-combobox-and-modalpopupextender.aspx
and the issue raised with the ModalPopupExtender in the first post.
Comments: This issue is fixed with release June 2012.
I have a blog post with pictures, details, and a workaround that is truly a hack:
http://weblogs.asp.net/peterblum/archive/2011/09/14/fixing-combobox-from-ajax-control-toolkit.aspx
Recommendation: Provide a Recalculate() client-side method that we can call when our javascript makes it visible.
Please also see this post which becomes relevant once you fix the visibility problem:
http://weblogs.asp.net/peterblum/archive/2011/09/16/more-with-ajax-control-toolkit-s-combobox-and-modalpopupextender.aspx
and the issue raised with the ModalPopupExtender in the first post.
Comments: This issue is fixed with release June 2012.