Hi i am a beginner in C sharp and trying to develop a wince 5.0 device application using C sharp.
i am using a thread in the Form1 Load method which is continously running a method named main_program
the problem is when i try to display any text on the textbox it shows the
exception message as follows. Control.Invoke must be used to interact with controls created on a seperate
thread.
as shown in the code below..
Please tell me how to resolve this problem...!!! CODE: - namespace biometric_device_app
-
{
-
public partial class Form1 : Form
-
{
-
public AsyncCallback pfnWorkerCallBack;
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public Socket m_socListener;
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public Socket m_socWorker;
-
-
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public Form1()
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{
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InitializeComponent();
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}
-
-
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Thread MainProgramThread;
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String entry = "";
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int toggle = 0;
-
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private void flashing(object sender, EventArgs e)
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{
-
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if (toggle == 0)
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{
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lbl_login.Text = "PRESS FINGER TO LOGIN";
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toggle = 1;
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}
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else
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{
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lbl_login.Text = "";
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toggle = 0;
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}
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}
-
-
-
-
-
private void main_program()
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{
-
-
-
while (true)
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{
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Thread.Sleep(500);
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switch (current_operation)
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{
-
-
-
case 0: // for finger print recognition
-
-
try
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{
-
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txt_show.Text = "hello";
-
-
if (!serialPort1.IsOpen)
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serialPort1.Open();
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serialPort1.ReadTimeout = 10000;
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int flag_0 = 0;
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int flag_no_match_0 = 1;
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byte[] value_search = new byte[28];
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byte[] info_0 = { 0x02, 0x00, 0x08, 0x32, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0xff, 0xc6, 0x03 };
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byte[] device_getnumb_0 = { 2, 0, 8, 0, 50, 77, 66, 73, 68 };
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byte[] no_match_0 = { 2, 0, 6, 57, 50 };
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again: serialPort1.Write(info_0, 0, 13);
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//Thread.Sleep(200); // 100 ms Delay after sending command
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serialPort1.Read(value_search, 0, 1);
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Thread.Sleep(5);
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serialPort1.Read(value_search, 1, 12);
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for (int b = 0; b < 9; b++)
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{
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if (!(value_search[b] == device_getnumb_0[b]))
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{
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flag_0 = 1;
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break;
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}
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else
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flag_0 = 0;
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}
-
-
if (flag_0 == 1)
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{
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for (int b = 0; b < 5; b++)
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{
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if (!(value_search[b] == no_match_0[b]))
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{
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flag_no_match_0 = 1;
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break;
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}
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else
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flag_no_match_0 = 0;
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}
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}
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/*
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while (flag == 1)
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{
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Thread.Sleep(200);
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goto again;
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}
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*/
-
-
-
-
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if (flag_0 == 0)
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{
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int num = value_search[9] * 256 + value_search[10];
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txt_show.Text = "EMPLOYEE NUMBER " + num + " LOGED IN";
-
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if (rad_btn_in.Checked)
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{
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entry = "IN";
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rad_btn_in.Checked = true;
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}
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else if (rad_btn_out.Checked)
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{
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entry = "OUT";
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rad_btn_out.Checked = true;
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}
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else ;
-
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/*
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while (!((rad_btn_in.Checked) || (rad_btn_out.Checked)))
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Thread.Sleep(100);
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*/
-
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StreamWriter rd = new StreamWriter(@"My Documents\Attendence.att", true);
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rd.WriteLine("LOGIN-----------" + "#" + "Employee Number: " + num + "#" + entry + "#" + DateTime.Now.ToString());
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rd.Close();
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}
-
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else if (flag_no_match_0 == 0)
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txt_show.Text = "NO MATCH FOUND";
-
-
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value_search = null;
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serialPort1.Close();
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flag_no_match_0 = 1;
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timer1.Enabled = true;
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}
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catch (Exception ex)
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{
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MessageBox.Show(ex.Message);
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}
-
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Thread.Sleep(1000);
-
-
-
break;
-
-
-
-
-
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case 1: // for enroll
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current_operation = 0;
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break;
-
-
case 2: // for lan recv
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current_operation = 0;
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break;
-
-
-
}
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}
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}
-
-
-
-
-
private void Form1_Load(object sender, EventArgs e)
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{
-
-
MainProgramThread = new Thread(new ThreadStart(main_program));
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MainProgramThread.Start();
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}
4  2807  TIP: When you are writing your question, there is a button on the tool bar that wraps the [code] tags around your copy/pasted code. It helps a bunch. Its the button with a '#' on it. More on tags. They're cool. Check'em out.
So often error messages are nearly worthless. How often have we seen messages that say something silly like "The unknown program has stopped for unknown reasons"?
But in this case your error message pretty well spells it out. Control.Invoke must be used to interact with controls created on a seperate thread. MSDN on control.invoke
Personally, I'm a fan of using anonymous methods for such things where possible. - void DoSomethingMethod()
-
{
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Invoke((MethodInvoker)delegate
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{
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// actually do the "something"
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});
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}
Hmmm, that error message seems pretty descriptive. You're trying to access members of Form1 from a separate thread. I think what you need to do is set up some form of communication from your thread running main_program, to the thread running Form1.
Can you use some kind of call back or event? I have not done much work with threads, but can you pass a parameter to the thread running main_program that tells it how to get back to Form1?
Don't take these as solutions, I'm just brainstorming out loud :)
I believe (since you really only get that exception in debugging) it also provides you with a direct link to MSDN about making threadsafe callbacks to the gui thread
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