Problems with threads and setting parents

Question

Hi! I have a threading problem. I have an MDI application with a main window and multiple child windows. My problem is as follows: I am using 2 child windows one for calculating stuff and writing the result to a file and another that plots the data from the calculated file. I have the main window running in one thread and the calculation running on another thread. What I want after the calculation is to open a plot window automatically and set its parent to be the main window. Now I get the error: Additional information: Controls created on one thread cannot be parented to a control on a different thread. The calculation thread is trying to open a child window and to set the parent to be the main window on another thread. I want the main window thread to open the child window. How can I do that from the calculation thread? Can I use events somehow? -Atle

shimtanny · Answer

Hi Controls provides therefore an mechanism with delegates. You have to use the Control.Invoke(..) method of the mdi parent form. Consider this small example: // Declare delegate who is able to invoke the mdi child. private delegate void CreateMdiChildDelegate(); private void MdiParent_Load(object sender System.EventArgs e) { // Create and start thread. Thread thread = new Thread(new ThreadStart(this.ThreadMethod)); thread.Start(); } private void ThreadMethod() { // Create delegate and assign method. CreateMdiChildDelegate createMdiChildDelegate = new CreateMdiChildDelegate(this.CreateMdiChild); this.Invoke(createMdiChildDelegate); } // Create and show mdi child invoked by the mdi parent. private void CreateMdiChild() { MdiChild child = new MdiChild(); child.MdiParent = this; child.Show(); } Hope i helped you. Cheers Simon