.net - MessageBox inside paint event high CPU -

i have custom listview, , wanted debug inside ondrawsubitem function displayng messagebox. expected gui freezing trying repaint item. weird thing cpu goes 100% when click subitem (after messagebox). can explain in loop has fallen this?

class listviewex : listview {     public listviewex()     {         this.setstyle(controlstyles.allpaintinginwmpaint | controlstyles.optimizeddoublebuffer | controlstyles.resizeredraw, true);     }     protected override void ondrawcolumnheader(drawlistviewcolumnheadereventargs e)     {         e.drawdefault = true;     }     protected override void ondrawsubitem(drawlistviewsubitemeventargs e)     {         messagebox.show("test");         e.drawdefault = true;     } } 

edit

if same paint event of button have not high cpu (just repeated messagebox)

    private void btntest_paint(object sender, painteventargs e)     {         messagebox.show("test");     } 

i know it's not right display mbox inside paint events. i'm curious different behaviour in 2 examples.

like alex's comment suggests, should never use message boxes debugging aid when you're working ui code. cause kinds of problems , mask behavior you're trying debug.

a better solution involves either 1 or combination of following:

• breakpoints in strategic locations
• debug.assert test assumptions
• debug.writeline print diagnostics output/immedate window