c# - Entering form modal message loop without actual form showing -

i have winforms application 1 main form mainform. application has scheduled operation being called in intervals. operation takes lot of time execute launched in background thread. when operation running form progress shown - loaderform. form shown modal via loader.showdialog(mainform); loader starts operation when shown.

this works fine unless operation starts when:

• mainform minimized in taskbar
• mainform hidden tray (not shown in taskbar @ all)

in such cases need not show loaderform unless application activated. problem loaderform shown when mainform not visually visible without proper handling.

what easiest way achieve desired behavior?

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example code

imports system.componentmodel   public class mainform      private sub timer_tick(sender object, e eventargs) handles uitimer.tick         uitimer.enabled = false         using loader = new loaderform()             loader.showdialog(me)         end using     end sub  end class  public class loaderform      private sub loaderform_shown(sender object, e eventargs) handles mybase.shown         worker.runworkerasync()     end sub      private sub worker_runworkercompleted(sender object, e runworkercompletedeventargs) handles worker.runworkercompleted         me.close()     end sub  end class 

we can create new modal message loop without showing modal dialog calling undocumented win32 apis beginmodalmessageloop , endmodalmessageloop.

note: these apis undocumented, not supposed use them. should use these last resort.

    //capture method reference using reflection     _methodbeginloop = findmethod(typeof (application), "beginmodalmessageloop");     _methodendloop = findmethod(typeof (application), "endmodalmessageloop");         private static methodinfo findmethod(type type, string methodname)             {                 const bindingflags binding_flags = bindingflags.static | bindingflags.nonpublic;                  memberinfo[] members = type.findmembers(membertypes.method, binding_flags,                     new methodfilter(methodname).matches, null);                  if (members.length == 1)                     return members[0] methodinfo;                 return null;             } 

for blocking inputs on main form, can use

application.openforms[0].invoke(new action(() =>  {    _methodbeginloop.invoke(null, null);  } 

for unblocking inputs on main form, can use

application.openforms[0].invoke(new action(() =>  {    _methodendloop.invoke(null, null);  }