Start thread with two parameters

Question

I've got a method that gets called on an event, which presents me with two variables varA, varB (both strings). This method gets called with new information quite frequently, thus I have created a separate method that takes in the two parameters. I want to run this method in a thread, however have struck the issue that Thread.Start will not accept parameters.

I've tried a few supposed methods, but have so far had no luck.. I think my best bet is to create a separate class, and handle it there.. However I have a List which I am inserting data into, and hit a dead end when the separate class tried to access that list, since it was in a different class.

Can someone help me out here please?

Answer 1

The start method of thread accepts an object parameter.

If your method accepts multiple parameters, then you can very well pass an object of your class containing the parameters into it. You can then unbox it in your method.

Thread.Start(Object)

http://msdn.microsoft.com/en-us/library/system.threading.thread.start.aspx

Update

In your case, try this,

string varC = varA + "," + varB;
Thread.Start(varC);

and in your method

string args[] = ((string)par).Split(',');

Answer 2

Hello, you can execute method with parameters in another thread in different ways: via Thread class, via System.ComponentModel.BackgroundWorker, via ThreadPool. If method gets called frequently, i think ThreadPool ll fit:

        ThreadPool.QueueUserWorkItem(
        (args)=>
            {
                try
                {
                //args - object, you can put in it string[] or
                // whatever you want

                // do work
                }
                catch(Exception e)
                {
                    // dont throw exceptions in this thread
                    // or application will crashed
                }
            }
        );

You can read about this classes on msdn:

http://msdn.microsoft.com/en-us/library/system.threading.threadpool.aspx

http://msdn.microsoft.com/en-us/library/system.threading.parameterizedthreadstart.aspx

http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx

Answer 3

Instead of using System.Thread, you could use a delegate.

e.g.:

public delegate void RunMyMethod(String a, String b);

RunMyMethod myDelegate = new RunMyMethod(MyMethod);
myDelegate.BeginInvoke(someAFromSomeWhere, someBFromSomeWhere);

Where MyMethod is the method you want to run, and the parameters are pulled from wherever necessary.

Answer 4

A simple solution...
This will print varA, varB to the console.

new RunTask<string, string>("varA", "varB").StartThread();

public class RunTask<TA, TB>
{
    public TA VarA { get; private set; }
    public TB VarB { get; private set; }

    public RunTask(TA varA, TB varB)
    {
        VarA = varA;
        VarB = varB;
    }
    public void StartThread()
    {
        ThreadPool.QueueUserWorkItem(Worker, this);
    }
    public void Worker(object obj)
    {
        var state = obj as RunTask<TA,TB>;
        Console.WriteLine(state.VarA + ", " + state.VarB);
    }
}

Edit:
If you want a solution where you need to update the UI this is probably a better solution.
And it is probably a better solution to put the arguments in a separate class like this.
Insert code to update list after the comment // Update List

public class ListForm : Form
{
    private static readonly object _listResultLock = new object();
    private readonly Action<TaskResult> _listResultHandler;

    public ListForm()
    {
        Load += ListForm_Load;
        _listResultHandler = TaskResultHandler;
    }

    private void ListForm_Load(object sender, EventArgs e)
    {
        new RunTask(new Task("varA", "varB", TaskResultHandler)).StartThread();
    }
    public void TaskResultHandler(TaskResult result)
    {
        if (InvokeRequired)
        {
            Invoke(_listResultHandler, result);
            return;
        }
        lock (_listResultLock)
        {
            // Update List
        }
    }
}

public class Task
{
    public Action<TaskResult> Changed { get; private set; }
    public string VarA { get; private set; }
    public string VarB { get; private set; }

    public Task(string varA, string varB, Action<TaskResult> changed)
    {
        VarA = varA;
        VarB = varB;
        Changed = changed;
    }
}
public class TaskResult
{
    public string VarA { get; private set; }
    public string VarB { get; private set; }

    public TaskResult(string varA, string varB)
    {
        VarA = varA;
        VarB = varB;
    }
}
public class RunTask
{
    private readonly Task _task;

    public RunTask(Task task)
    {
        _task = task;
    }
    public void StartThread()
    {
        ThreadPool.QueueUserWorkItem(Worker, _task);
    }
    public void Worker(object obj)
    {
        var state = obj as Task;
        if (state == null) return;
        if (state.Changed == null) return;
        state.Changed(new TaskResult("this is " + state.VarA, "this is " + state.VarA));
    }
}

Answer 5

If you know what will be supplied to the thread, then you may want to pass objects to it.

Read more here -> http://msdn.microsoft.com/en-us/library/6x4c42hc.aspx

Example:

void someFunction()
{
    Thread t = new Thread(doWork);

Then,

    t.Start(new int[] { 1, 2 }); //two values passed to the thread.

Or,

    t.Start(1); //one value passed to the thread.
}

Now, the method -

void doWork(object data)
{
    System.Collections.IList list = data as System.Collections.IList;
    if (list != null)
    {
        object[] _objArr = data as object[];
        foreach (object io in list)
        {
            System.Diagnostics.Trace.WriteLine(io);
        }
    }
    else
    {
        System.Diagnostics.Trace.WriteLine(data);
    }
}