Cross-Thread operation not valid: Control... An error in c#

Hi,


You are getting this error because you are trying to make UI changes on a secondary thread.

Try this link.

http://msdn.microsoft.com/en-us/library/zyzhdc6b.aspx[^]

You will have to do a check.

here are the code required.

class checkLock
    {

        private delegate void ShowHideFormCallback(bool Show); //HERE

        ScreenSaver s = new ScreenSaver();
        public void checkLocks()
        {
            while(true){
            try
            {
               if (DBConnect.isExists("some checking in database..."))
                {
/* show the screensaver when the value in the database changes to open */
                   // s.Show();
                   ShowHideForm(true);//HERE
                }
                else
                {
/* Hide the screensaver when the value in the database changes to open */
                    //s.Hide();
                   ShowHideForm(false);//HERE
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            Thread.Sleep(400);
            }
        }

        //HERE
        private void ShowHideForm(bool Show)
        {
           if (s.InvokeRequired)
           {
              s.Invoke(new ShowHideFormCallback(ShowHideForm),Show);

           }
           else
           {
              if (Show)
              {
                s.Show();
              }
              else
              {
                s.Hide();
              }

           }
           
        }

    }

Regards

Terence

Hi,
Cross-thread operation not valid - it is an error which normally appears when you try to access a control from a thread which did not create the control.
I'm not sure about the controls from your checkLock but it seems that hide/show methods try to modify some internal properties of object s (if you pay attention you can see that s is created in main thread, and then is accessed from the second thread. There are 2 solutions for this problem: 1) you can create your checkLock object in the same thread which calls the checkLocks() method, or 2) I would prefer using BeginInvoke() instead of creating a new thread:

public partial class client : Form
    {
       public static bool locks= false;
       
        public client()
        {
            InitializeComponent();
            checkLock cl = new checkLock();
            BeginInvoke(new Action(()=>
                        {
                             cl.checkLocks();
                        }));
        }     
    }

More about BeginInvoke - http://msdn.microsoft.com/en-us/library/0b1bf3y3.aspx[^]

Regards