Passing in a string to a thread I am about to start? [C# 2002]

[Shaitan00]

I am trying to accomplish something like this:

{
   string sType ="Update";
   Thread th1 = new Thread (new ThreadStart(Operation1(sType)));
   th1.Start();
}

private void Operaton1(string sType)
{
   if (sType == "Update")
   {
   }
   else
   {
   }
}

Obviouslly this doesn't work and returns and error message as follows:
Method name expected

It works fine if my "Operation1" has no parameters but I somehow need to pass the information from "sType" into the Thread itself...
How could I accomplish passing a STRING into a THREAD I am about to start?

Any help would be greatly appreciated.
Thanks,

[nmadd]

Hi there,
I'm certainly no expert in threading, but I read up a little bit and using your version of the framework you can consider storing your variable in an instance of a class. So perhaps something like this:

// My form.
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        // New instance of my other class.
        private void button1_Click(object sender, EventArgs e)
        {
            string str = "Update";
            MyOperations op = new MyOperations(str);
            new Thread(new ThreadStart(op.Operation1)).Start();
        }
    }
 
    // My other class.
    public class MyOperations
    {
        string _str;
 
        public MyOperations (string str)
        {
            this._str = str;
        }
 
        public void Operation1()
        {
            if (_str == "Update")
            {
                MessageBox.Show("Update.");
            }
            else
            {
                MessageBox.Show("No update.");
            }
        }
    }

I did find many sites that spoke about this topic in my search with much more information. Give Google a go and I'm sure you'll find plenty. I hope this little gets you started.

[Shaitan00]

Thats a great idea - and while trying to implement it I ran into a single roadblock - Operation1 uses functions part of the class that is spawning the thread - if I pass in a class.function as opposed to a local function I loose scope of these functions and can no longer launch them (from what I can see). For example ... using your code ...

// My form.
public partial class Form1 : Form
{
	public Form1()
	{
		InitializeComponent();
	}
	
	// New instance of my other class.
	private void button1_Click(object sender, EventArgs e)
	{
		string str = "Update";
		MyOperations op = new MyOperations(str);
		new Thread(new ThreadStart(op.Operation1)).Start();
	}

	private delegate void DoTheWorkDelegate
	private void DoTheWork(string sStuff)
	{
		// DoTheWork stuff
		// This can be called by a thread using “DoTheWorkDelegate”
	}
}

// My other class.
public class MyOperations
{
	string _str;
	public MyOperations (string str)
	{
		this._str = str;
	}
	
	public void Operation1()
	{
		if (_str == "Update")
		{
			DoTheWork(“update”);
		}
		else
		{
			DoTheWork(“not update”);
		}
	}
}

So doing it that way I get errors because "DoTheWork" is not defined in the new class "MyOperations" - any clue how to solve this aside from passing the "this" into the "MyOperations" class also and doing something like this.DoTheWork? (as I am not sure how threadsafe that kind of request would be).

Thanks,

[Atheist]

Heres a simple example of passing a string to a thread:

private void Form1_Load(object sender, EventArgs e)
        {
            System.Threading.Thread thr1 = new System.Threading.Thread(DoWork);
            thr1.Start("Hello");
 
        }
 
        private void DoWork(object obj)
        {
            string Message = Convert.ToString(obj);
            MessageBox.Show(Message);
        }

[nmadd]

Heres a simple example of passing a string to a thread:

private void Form1_Load(object sender, EventArgs e)
        {
            System.Threading.Thread thr1 = new System.Threading.Thread(DoWork);
            thr1.Start("Hello");
 
        }
 
        private void DoWork(object obj)
        {
            string Message = Convert.ToString(obj);
            MessageBox.Show(Message);
        }

Wow, that was quite easy. I can't believe that in all of sites that I looked on regarding passing a parameter to a new thread, that I didn't see that. All of them mentioned something with a class.

Is this also available in 1.1? I'm not sure how the documentation on MSDN is exactly for 1.1, but they don't show an Overload for this method.

[jmcilhinney]

If you want to be able to execute a method of an object you have no reference to then you need to pass a delegate. The very reason that delegates exist is to enable executing methods without references to their owners. Create a DoTheWorkDelegate instance and pass it to your MyOperations object, from which it can be invoked.

[Shaitan00]

jmcilhinney: How do you pass in a delegate to a thread?

As it stands the solution I found was to pass in the "this" pointer to the thread so that I can access all the required functions - and in the spawning class I created delegates for each function based on the Invoke requirements. I did a quick test and it looks like, when in my thread, if I do something like fMain.DoSomething the thread will go to the calling class and be Invoked and then run the function.

Is this also a correct and threadsafe way to do it?