Event Handler
in [CSharp]
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From: Anders Eriksson on 18 Nov 2009 04:52 Hello, I use an COM server that creates a number of events. I have created a class that controls the COM server and that receives the events, it's called LaserCtrl. This works! I have a form that uses LaserCtrl and I want to update a textbox in the form from LaserCtrl. The constructor of LaserCtrl looks like this private TextBox msg; public LaserCtrl(TextBox m) { msg = m; } From a normal method in LaserCtrl this works perfectly msg.Text = "my nice message"; BUT from the EventHandler method nothing happens! I'm guessing that this is because the eventhandler method is in another thread? How do I solve this? // Anders -- English is not my first language, so any insults or strangeness is due to the translation! -- -- Anders Eriksson DC Lasersystem Software Engineer 073 029 45 74 anders(a)dclasersystem.com
From: Alberto Poblacion on 18 Nov 2009 05:17 "Anders Eriksson" <andis.eriksson(a)gmail.com> wrote in message news:31C7C55D-E3E9-430F-983B-A65509CD949E(a)microsoft.com... > From a normal method in LaserCtrl this works perfectly > msg.Text = "my nice message"; > > BUT from the EventHandler method nothing happens! I'm guessing that this > is because the eventhandler method is in another thread? Yes, if the event handler is running in another thread, you have to marshall execution into the thread that created the control before you can change it. One way to do this is by means of its Invoke method: msg.Invoke(new MethodInvoker(WriteMyText)); .... private void WriteMyText() { msg.Text = "my nice message"; }
From: Anders Eriksson on 18 Nov 2009 05:28 Hello Alberto, > Yes, if the event handler is running in another thread, you have to > marshall execution into the thread that created the control before you can > change it. One way to do this is by means of its Invoke method: > > msg.Invoke(new MethodInvoker(WriteMyText)); > ... Two questions. 1. The msg.Invoke should I call it from my eventhandler? 2. How would I do this if I need to have two parameters? E.g WriteMyText(String msg, Boolean clr) // Anders
From: Alberto Poblacion on 18 Nov 2009 06:04 "Anders Eriksson" <andis.eriksson(a)gmail.com> wrote in message news:eR$IZnDaKHA.2160(a)TK2MSFTNGP02.phx.gbl... > Two questions. > 1. The msg.Invoke should I call it from my eventhandler? > 2. How would I do this if I need to have two parameters? E.g > WriteMyText(String msg, Boolean clr) 1. Yes, you call theControl.Invoke from the code that is running in the other thread, in this case your eventhandler. 2. Invoke takes actually a System.Delegate parameter, so you can use any delegate instead of MethodInvoker. I am showing below some code that works with any version of C# including 1.0, but if you have a newer version you can simplify the code by means of anonymous delegates or lambdas. delegate void MyInvoker(String msg, Boolean clr); .... msg.Invoke(new MyInvoker(MyRoutine), new object[]{valueformsg, valueforclr}); .... private void MyRoutine(String msg, Boolean clr) { ... }
From: Anders Eriksson on 18 Nov 2009 07:15 Hello Alberto, Thank you very much! Everything works! // Anders --
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