winforms - VB.NET events handling in deep -


anybody know how events works in vb.net doubt happen if event code doesn't finish of handle event , new 1 happen.

i.e.: have doubleclick event , user make repeatedly , insistently double click lot of times fast.

the event code calls sub routines , functions in same form(not multi threading)

the event code restart form top or wait until finish , re enter when code executed?

today catch following 2 errors

error 1:

error al crear identificador de ventana. en system.windows.forms.nativewindow.createhandle(createparams cp) en system.windows.forms.control.createhandle() en system.windows.forms.control.createcontrol(boolean fignorevisible) en system.windows.forms.control.createcontrol() en system.windows.forms.control.controlcollection.add(control value) en system.windows.forms.tabcontrol.controlcollection.add(control value) en system.windows.forms.tabcontrol.tabpagecollection.insert(int32 index, tabpage tabpage) en commands.form1.datagridviewalarms_cellmousedoubleclick(object sender, datagridviewcellmouseeventargs e)

error 2:

error al crear identificador de ventana. en system.windows.forms.nativewindow.createhandle(createparams cp) en system.windows.forms.control.createhandle() en system.windows.forms.control.get_handle() en system.windows.forms.control.creategraphicsinternal() en system.windows.forms.threadexceptiondialog..ctor(exception t) en system.windows.forms.application.threadcontext.onthreadexception(exception t) en system.windows.forms.control.wndprocexception(exception e) en system.windows.forms.control.controlnativewindow.onthreadexception(exception e) en system.windows.forms.nativewindow.callback(intptr hwnd, int32 msg, intptr wparam, intptr lparam) en system.windows.forms.unsafenativemethods.intcreatewindowex(int32 dwexstyle, string lpszclassname, string lpszwindowname, int32 style, int32 x, int32 y, int32 width, int32 height, handleref hwndparent, handleref hmenu, handleref hinst, object pvparam) en system.windows.forms.unsafenativemethods.createwindowex(int32 dwexstyle, string lpszclassname, string lpszwindowname, int32 style, int32 x, int32 y, int32 width, int32 height, handleref hwndparent, handleref hmenu, handleref hinst, object pvparam) en system.windows.forms.nativewindow.createhandle(createparams cp) en system.windows.forms.control.createhandle() en system.windows.forms.tabcontrol.createhandle() en system.windows.forms.control.createcontrol(boolean fignorevisible) en system.windows.forms.control.createcontrol(boolean fignorevisible) en system.windows.forms.control.createcontrol(boolean fignorevisible) en system.windows.forms.control.createcontrol() en system.windows.forms.control.controlcollection.add(control value) en system.windows.forms.tabcontrol.controlcollection.add(control value) en system.windows.forms.tabcontrol.tabpagecollection.insert(int32 index, tabpage tabpage) en commands.form1.datagridviewalarms_cellmousedoubleclick(object sender, datagridviewcellmouseeventargs e)

this errors doesn't happen have 20 machines same program , 1 user have problems , happen when double click repeatedly fast.

i'm removing tappages following code

dim currenttab tabpage = alarmstabcontrol.selectedtab alarmstabcontrol.tabpages.remove(currenttab)

the winform framework single-threaded. such, events processed on single-thread. therefore, when event handler called, no other event handlers called until first 1 has completed. in other words, event handlers called in serial fashion.

the way event handler can interrupted event if actively relinquishes control calling application.doevents. can imagine, calling doevents can cause unexpected behavior. since calling doevents typically leads bugs, discouraged , panned sign of poor design. in such cases, sign using backgroundworker more appropriate.

a little deeper

ui-related events triggered when window messages received operating system. incoming window messages added queue. responsibility of each process read window messages queue , handle them appropriately. typically done in message loop processes each message in queue in order, or idles until new message received. each time message loop finds new message processed, calls window procedure. window procedure typically called windowproc or wndproc. in .net winform projects, message loop initiated calling application.run.


-

Comments

Post a Comment

Popular posts from this blog

html - Sizing a high-res image (~8MB) to display entirely in a small div (circular, diameter 100px) -

first of all, thank being patient know simple question more couple of weeks' experience figure out. i've seen folks persevere , helpful on here , hope you're willing me. here fiddle: http://jsfiddle.net/65uzf/ here 1 of places searched answers on here: ( vertically center image thumbnails fix-sized div ) tried solutions on there , didn't work out me. i've searched ~4 or 5 others, , been unsuccessful those, too. what want take large image (what linked background-image #ysypic , #tabpic divs) , display thumbnail version of image in confines of divs have set it. is, using background properties have laid out in css, portion of image displays inside of circular divs. without these properties, display defaults smaller section of image [presumably pi*(50^2) area in top left] terrible resolution. i not care if entire image doesn't display inside of circles (it won't, given difference in shape), , overflow not being displayed fine. want able see figu
Read more

java - IntelliJ - No such instance method -

using intellij's 12 ultimate, i'm running following code in debugger: java import play.api.libs.json.jsvalue; public class foo { ... public jsvalue tojson() { ... } public class fooexample { ... foo foo = new foo(); system.out.println("...); //<-- breakpoint at breakpoint, right-clicked source code , picked "evaluate expression," typing in: foo.tojson() . but following error showed up: no such instance method: play.api.libs.json.jsvalue$class.com.foo.foo.tojson () am doing wrong? foo#tojson calls scala code, if matters. edit had breakpoint after instantiation of foo. downvoted it, deserved it. edit my answer no longer valid after op modified question (i.e. moved breakpoint actual is).. a breakpoint hit before line executed. in case foo has not yet been declared or instantiated (i.e. foo constructor has not yet been called). you'll need put breakpoint @ next line (or step on current line) if want evaluate foo .
Read more

identifier - Is it possible for an html5 document to have two ids? -

i wondering if html5 element can have 2 ids, this: <button id="thing1" id="thing2" name="button1" onclick="change()">click here</button> or this: <button id="thing1, thing2" name="button1" onclick="change()">click here</button> also, if 1 of ids said 1 thing, , other id said thing, 1 used? tl;dr : no. in versions of html, each element can have 1 id. see the spec : the id attribute specifies element's unique identifier (id). [dom] the value must unique amongst ids in element's home subtree , must contain @ least 1 character. the value must not contain space characters. note: there no other restrictions on form id can take; in particular, ids can consist of digits, start digit, start underscore, consist of punctuation , etc. note: element's unique identifier can used variety of purposes, notably way link specific parts of document usin
Read more