Windows Forms Designer, AutoToolboxPopulate Property Performance
When the Windows Forms Designer, AutoToolboxPopulate = True for solutions with multiple projects having many user controls, reports and datasets causes huge performance degradation when the toolbox is first opened.
bohuang [MSFT] commented
We made a lot of toolbox performance improvement in VS2012. Give it a try and let me know if it fixes your issue.
You can get more details from this blog: http://blogs.msdn.com/b/visualstudio/archive/2012/07/16/improved-toolbox-performance-delivers-highly-responsive-visual-studio-2012.aspx
I have the same problem and you can't turn AutoToolboxPopulate off because then it takes even longer to add a user control to a form.
I'd like an option to ignore datasets when populating the toolbox since as well as taking ages it clutters up the toolbox.