c# - Cross-thread operation not valid when using Invoke -

i've made chat system , got error:

cross-thread operation not valid: 'messagebox' etc.

what have done: i've added invoke. here code:

invoke(new action(() => messagebox.items.add(usersname.text + ": " + receivedmessage))); 

the problem is, sends message other user blank. because i'm connected chat locally. here picture:

receiving messages:

private void messagecallback(iasyncresult aresult) {     try     {         byte[] receiveddata = new byte[1500];         receiveddata = (byte[])aresult.asyncstate;         asciiencoding aencoding = new asciiencoding();         string receivedmessage = aencoding.getstring(receiveddata);         invoke(new action(() => messagebox.items.add(usersname.text + ": " + receivedmessage)));         buffer = new byte[1500];         socket.beginreceivefrom(buffer, 0, buffer.length, socketflags.none, ref theirip, new asynccallback(messagecallback), buffer);     }     catch (exception ex)     {         messagebox.show(ex.message);     } } 

sending messages:

private void sendbtn_click(object sender, eventargs e) {     try     {         if (messagetb.text == "")         {             return;         }         else         {             asciiencoding eencoding = new asciiencoding();             byte[] msg = new byte[1500];             msg = eencoding.getbytes(messagetb.text);             socket.send(msg);             messagebox.items.add(yourname.text + ": " + messagetb.text);             messagetb.clear();         }     }     catch (exception ex)     {         messagebox.show(ex.message);     }     this.activecontrol = messagetb; } 

this exception occurs whenever trying access control in different thread other form's main thread.

i use bellow simple log mechanism, suitable simple application.

    private delegate void logdelegate(listbox messagebox, string data);      private logdelegate _logdelegate;     private void log(listbox messagebox, string data)     {         if (messagebox.invokerequired)         {             logdelegate logdelegate = log;             invoke(logdelegate, messagebox, data);         }         else         {             messagebox.items.add(data);         }     }      public form1()     {         initializecomponent();         //don't forget, initialize delegate         _logdelegate = log;     }      private void btn_start_click(object sender, eventargs e)     {            log("anything log");     }     private void messagecallback(iasyncresult aresult)     {         try         {             //instead of invoke use              //invoke(new action(() => messagebox.items.add(usersname.text + ": " + receivedmessage)));             log("anything log");          }         catch (exception ex)         {             messagebox.show(ex.message);         }     } 

as said, code can used anywhere , simple. more complex logging mechanism , better performing use log4net or nlog.