Cross-thread operation not valid - used timer to do someting, but can't hide the form

Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on.

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using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Timers; 
 
namespace WindowsFormsApplication2

{

    public partial class Form1 : Form

    {

        private static System.Timers.Timer aTimer;
 
        public Form1()

        {

            InitializeComponent();

            aTimer = new System.Timers.Timer();

            aTimer.Elapsed += new ElapsedEventHandler(found_card);

            // Set the Interval to 2 seconds.

            aTimer.Interval = 1000;                     

            aTimer.Enabled = true;          
 
        }
 
        private void found_card(object sender, EventArgs e)

        {

            aTimer.Enabled = false;
 
            // use smart card system to find the card. if found the card, it will open form2 and close form1            
 
            Form form2 = new Form2();

            this.Hide();  // <--- error, please help me to make a solution

            form2.ShowDialog();

            this.Close();                

        }

    }

}

Nov 17 '09 #1

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3895

Plater

7,872

Expert 4TB

That exception only gets thrown in debug mode, to alert you of what you are doing.
In the exception message should be a link to MSDN about ways to solve that issue.
My favorite is using a delegate and invoke.

For instance in my form I have:

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private delegate string ReportInfoCallback(string msg);
 
private string ReportInfo(string msg)

{

  if (this.InvokeRequired)

  {

    ReportInfoCallback d = new ReportInfoCallback(ReportInfo);

    this.Invoke(d, msg);

  }

  else

  {

    tbResults.AppendText(msg);

  }

  return msg;

}

Now from another thread (like a timer) I can call the ReportInfo("Some text"); function and it will handle the cross threading.

You can change up the function and the delegate to match your needs for hiding.

I see that you are also calling this.Close(), once that happens your timer dissapears too

Nov 18 '09 #2

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