trying to understand classes and threads using the progress bar in c# - C# Discussion Boards

trying to understand classes and threads using the progress bar in c#

3-Feb-10 7:37

This has been stated quite a few times, format your code (using the pre tags) or it will just get ignored.

I know the language. I've read a book. - _Madmatt

tonyonlinux3-Feb-10 6:15

tonyonlinux

3-Feb-10 6:15

I'm trying to make a class that will simply put the progress bar in a loop (just to see how it works for learning purposes). I keep getting the following error though and I don't understand why.

error

Cross-thread operation not valid: Control 'progressBar1' accessed from a thread other than the thread it was created on.

here is the class code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms; // remove after testing used to show message boxes
using System.Threading;

namespace WindowsFormsApplication1
{



    public partial class thread
    {
        //Properties
        private thread trd;
        private ProgressBar _threadProgressBar;

        public ProgressBar ThreadProgressBar
        {
            set { _threadProgressBar = value; }
            get { return _threadProgressBar; }
        }
        public void startthread()
        {
            
            
            Thread trd = new Thread(new ThreadStart(this.ThreadTask));
            trd.IsBackground = true;
            trd.Start();
        }



        private void ThreadTask()
        {

            int stp;
            int newval;
            Random rnd = new Random();

            while (true)
            {
                stp = ThreadProgressBar.Step * rnd.Next(-1, 2);
                newval = ThreadProgressBar.Value + stp;

                if (newval > ThreadProgressBar.Maximum)
                    newval = ThreadProgressBar.Maximum;
                else if (newval < ThreadProgressBar.Minimum)
                    newval = ThreadProgressBar.Minimum;

                ThreadProgressBar.Value = newval;

                Thread.Sleep(100);
            }
        }
    }
}

i'm calling it inside a windows form
with

public void callthread()
        {
            thread mythread = new thread();
            mythread.ThreadProgressBar = progressBar1;
            mythread.startthread();
        }

thanks

Re: trying to understand classes and threads using the progress bar in c#

Luc Pattyn3-Feb-10 6:28

Re: trying to understand classes and threads using the progress bar in c#

3-Feb-10 6:28

Seems I wrote this[^] especially for you. Laugh | :laugh:

BTW: entering the error message in the Google search box usually leads to the solution right away.

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

Not Active3-Feb-10 6:33

Re: trying to understand classes and threads using the progress bar in c#

3-Feb-10 6:33

Just for him? Do you take requests Poke tongue | ;-P

I know the language. I've read a book. - _Madmatt

Luc Pattyn3-Feb-10 6:42

Re: trying to understand classes and threads using the progress bar in c#

3-Feb-10 6:42

Mark Nischalke wrote:
Do you take requests

Not normally. I do take hints though.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

tonyonlinux3-Feb-10 10:18

tonyonlinux

3-Feb-10 10:18

haha thanks for taking the time and writing that article just for me. I feel special Smile | :)

Anyway, thanks again.

How to bind control’s properties to variables in C#?

PomaPomaPoma3-Feb-10 5:48

Re: How to bind control’s properties to variables in C#?

3-Feb-10 5:48

I have form with lot's of TextBoxes and also there is a lot of threads in my program that need to read content's of those TextBoxes (settings). Since I can't access controls from other threads, I decided to make special class that will hold all the settings, and if user changes some, control will invoke OnTextChanged event and change corresponding value in class. But if I use that approach there will be a lot of similar handlers tike this

private void txtCrap1_TextChanged(object sender, EventArgs e) 
{ 
    Settings.Crap1 = txtCrap1.Text; 
}

What I want is to do something like this

private void SetUpControlBindings() 
{ 
    AddBinding(txtCrap1, Settings.Crap1); 
    AddBinding(txtCrap2, Settings.Crap2); 
} 
private void AddBinding(object control, object value) 
{ 
    //Add entry to some kind of dictionary 
} 
private void UpdateValue(object sender, EventArgs e) 
{ 
    if (sender is TextBox) 
    { 
    //Search it in dictionary and change appropriate value 
    } 
}

But I can't find any pointers to variables in C# Any ideas how to do this?
Actually my program is a bit more complicated. I have not only textboxes, but CheckBoxes, NumericUpDowns etc. also I want my Settings class to hold some additional objects like Lists.

P.S. I can't use reflection since my code will be obfuscated after compilation

Luc Pattyn3-Feb-10 9:23

Re: How to bind control’s properties to variables in C#?

3-Feb-10 9:23

Hi,

it is pretty easy to create a method that returns the Text (or any other property) of a Control, even from an unrelated thread. Look for "Retrieving information from a Control" in this article[^].

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

PomaPomaPoma3-Feb-10 9:52

Re: How to bind control’s properties to variables in C#?

3-Feb-10 9:52

I can't do it because threads will read settings in a loop, much more often than settings will change. So if I'll use Invoke it will cause big performance problems.

Luc Pattyn3-Feb-10 9:59

Re: How to bind control’s properties to variables in C#?

3-Feb-10 9:59

then make a local copy before entering the loop, and possibly update every so often.

most of the time, my apps have several controls and a "start" button, control values only get read when "start" is clicked, i.e. the job definition is static. When it has to be dynamic, I always consider using a Forms.Timer to update a set of variables periodically, i.e. I don't invest in data bindings if I can avoid them easily.

However, if you want it truly event-driven and are willing to databind everything, that is just fine.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

PomaPomaPoma3-Feb-10 11:12

Re: How to bind control’s properties to variables in C#?

3-Feb-10 11:12

Yeah, that's a good idea. I think i'll do like you saying Smile | :)

Not Active3-Feb-10 9:32

Re: How to bind control’s properties to variables in C#?

3-Feb-10 9:32

Why do you need to create several OnTextChange even handlers? One is all you need.

private void TextChanged(object sender, EventArgs e) 
{ 
    TextBoxctrl = sender as TextBox;
    Settings[ctrl.Tag] = ctrl.Text;
} 

private Dictionary<string, string> Settings{get; set;}

Add the tag to each textbox that will correspond the to dictionary key.

I know the language. I've read a book. - _Madmatt

PomaPomaPoma3-Feb-10 10:09

Re: How to bind control’s properties to variables in C#?

3-Feb-10 10:09

To use dictionary for settings is a good idea, but I need to stote not only TextBox.Text but also Checkbox.Checked, NumericUpDown.Value, TextBox.Lines etc. So if I'll use dictionary it will result in lot's of type casts. Maybe you can modify your method to take this into account?

Not Active3-Feb-10 10:17

C# code clean up and improvement

3-Feb-10 10:17

PomaPomaPoma wrote:
Maybe you can modify your method to take this into account?

No, it's your project. If you want me to do your work email and we'll discuss rates.

I know the language. I've read a book. - _Madmatt

eeffoc423-Feb-10 5:20

eeffoc42

3-Feb-10 5:20

Hi All,

I’m teaching myself C# and I’ve written a small application that that I use to retrieve some computer information using WMI.

The application is working and returns the information I want. My question is, because I am just learning, would someone be willing to look at my code and suggest areas where I could improve what I have written?

I’m fairly sure that there are probably better more efficient ways to do what I’ve written.

Thanks
Rob

Re: C# code clean up and improvement

Luc Pattyn3-Feb-10 5:26

Re: C# code clean up and improvement [modified]

3-Feb-10 5:26

If you were to show say 20 to 40 lines of it (inside PRE tags!), you likely get feedback right here.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.
[The QA section does it automatically now, I hope we soon get it on regular forums as well]

eeffoc423-Feb-10 5:50

eeffoc42

3-Feb-10 5:50

Here is some of the code I used to get some BIOS info and display it.

//Perform the search for WMI Info
private void SearchWMI_Data(string hostName)
{
    this.listBox1.Items.Clear();
    this.queueStack.Clear();

    string myString = "";
    string target = hostName;
    long ramSize = 0;
    IPAddress[] myIP = Dns.GetHostAddresses(target);

    try
    {
        if (!this.ValidateHostInput(hostName)) return;
        {
            ManagementScope scope = new ManagementScope("\\\\" + target + "\\root\\cimv2");
            ManagementPath pathBios = new ManagementPath("Win32_Bios");
            ManagementPath pathSystem = new ManagementPath("Win32_ComputerSystem");
            ObjectGetOptions obj = new ObjectGetOptions(null);

            ManagementClass wmiBios = new ManagementClass(scope, pathBios, obj);
            ManagementClass wmiSystem = new ManagementClass(scope, pathSystem, obj);

            foreach (IPAddress theIP in myIP)
            {
                queueStack.Enqueue("IP Address: " + theIP.ToString());
            }

            foreach (ManagementObject bios in wmiBios.GetInstances())
            {
                //Add info to a Queue stack
                queueStack.Enqueue("");
                queueStack.Enqueue("=== BIOS Info ===");
                try
                {
                    queueStack.Enqueue("Manufacturer: " + bios.Properties["Manufacturer"].Value.ToString().Trim());
                }
                catch
                {
                    queueStack.Enqueue("Manufacturer: Error reading status");
                }
                try
                {
                    queueStack.Enqueue("SN: " + bios.Properties["Serialnumber"].Value.ToString().Trim());
                }
                catch
                {
                    queueStack.Enqueue("SN: Error reading status");
                }
            }

            //Get data from the Queue stack
            while (this.queueStack.Count > 0)
            {
                this.listBox1.Items.Add(this.queueStack.Dequeue());
            }
        }
        txtBoxHostName.Focus();
    }
    catch
    {
        this.listBox1.Items.Add("Unable to find the specified computer: " + hostName.ToUpper());
        txtBoxHostName.Focus();
    }
}

modified on Wednesday, February 3, 2010 12:27 PM

Re: C# code clean up and improvement

Luc Pattyn3-Feb-10 6:26