multithreading - How to reset a textbox in WPF in a button handler before doing something else? -

i have simple wpf button , textbox in wpf application(not using mvc or binding @ all). able following upon clicking button:

1) clear textbox

2) create result

3) assign result textbox

i used textbox.clear, textbox.text= string.empty, delegates , dispatcher approach like

private void button_click(object sender, routedeventargs e)     {         application.current.dispatcher.begininvoke(new action (clearreporttxtbox), dispatcherpriority.send);         system.threading.thread.sleep(5000);         runtest();     }   private void clearreporttxtbox()     {         report_textbox.text = string.empty;     } 

none of them working correctly me. dispatcher method somehow working not wish. seems clear task queued , when actions in button click handler finished, come play , delete textbox, causes generated report , assigned textbox (created runtest in code above) deleted well. hence late delete action , eliminate whole result.

currently seems me clicking on button uithread blocks , takes control. dispatcher queue delete action next action after finishing button click.

is possible force delete @ beginning , rest? reach pause button activity , delete @ first action , continue rest of actions in button handler.

am doing wrong?

thank in advance.

the "dispatcher.begininvoke" kinda weird want do

all ui update has done on main thread. since "button_click" event executing on main thread, delegate push dispatcher can executed after button_click handle completed. that's why execution sequence becomes 1. gui freeze because thread.sleep 2. runtest 3. clearreporttextbox

guess can try sth following instead.

    private void buttonbase_onclick(object sender, routedeventargs e)     {                     clearreporttxtbox();          task.factory.startnew(runtest);     }      private void clearreporttxtbox()     {         mytextbox.text = string.empty;     }      private void runtest()     {         system.threading.thread.sleep(5000);          if (dispatcher != null && !dispatcher.checkaccess())         {             dispatcher.invoke(priority, ()=> mytextbox.text = "123");         }         else         {             mytextbox.text = "123";         }                     }