How do you put an object in another thread?

is there any way in c# to put objects in another thread? All I found is how to actually execute some methods in another thread. What I actually开发者_C百科 want to do is to instanciate an object in a new thread for later use of the methods it provides.

Hope you can help me, Russo

Objects do not really belong to a thread. If you have a reference to an object, you can access it from many threads.

This can give problems with object that are not designed to be accessed from many threads, like (almost all) System.Windows.Forms classes, and access to COM objects.

If you only want to access an object from the same thread, store a reference to the thread in the object (or a wrapping object), and execute the methods via that thread.

There seems to be some confusion about how threads work here, so this is a primer (very short too, so you should find more material before venturing further into multi-threaded programming.)

Objects and memory are inherently multi-thread in the sense that all threads in a process can access them as they choose.

So objects do not have anything to do with threads.

However, code executes in a thread, and it is the thread the code executes in that you're probably after.

Unfortunately there is no way to just "put an object into a different thread" as you put it, you need to specifically start a thread and specify what code to execute in that thread. Objects used by that code can thus be "said" to belong to that thread, though that is an artificial limit you impose yourself.

So there is no way to do this:

SomeObject obj = new SomeObject();
obj.PutInThread(thatOtherThread);
obj.Method(); // this now executes in that other thread

In fact, a common trap many new multi-thread programmers fall into is that if they create an object in one thread, and call methods on it from another thread, all those methods execute in the thread that created the object. This is incorrect, methods always executes in the thread that called them.

So the following is also incorrect:

Thread 1:
    SomeObject obj = new SomeObject();

Thread 2:
    obj.Method(); // executes in Thread 1

The method here will execute in Thread 2. The only way to get the method to execute in the original thread is to cooperate with the original thread and "ask it" to execute that method. How you do that depends on the situation and there's many many ways to do this.

So to summarize what you want: You want to create a new thread, and execute code in that thread.

To do that, look at the Thread class of .NET.

But be warned: Multi-threaded applications are exceedingly hard to get correct, I would not add multi-threaded capabilities to a program unless:

1. That is the only way to get more performance out of it
2. And, you know what you're doing

All threads of a process share the same data (ignoring thread local storage) so there is no need to explicitly migrate objects between threads.

internal sealed class Foo
{
    private Object bar = null;

    private void CreateBarOnNewThread()
    {
        var thread = new Thread(this.CreateBar);

        thread.Start();

        // Do other stuff while the new thread
        // creates our bar.
        Console.WriteLine("Doing crazy stuff.");

        // Wait for the other thread to finish.
        thread.Join();

        // Use this.bar here...
    }

    private void CreateBar()
    {
        // Creating a bar takes a long time.
        Thread.Sleep(1000);            

        this.bar = new Object();
    }
}

All threads can see the stack heap, so if the thread has a reference to the objects you need (passed in through a method, for example) then the thread can use those objects. This is why you have to be very careful accessing objects when multi-threading, as two threads might try and change the object at the same time.

There is a ThreadLocal<T> class in .NET that you can use to restrict variables to a specific thread: see http://msdn.microsoft.com/en-us/library/dd642243.aspx and http://www.c-sharpcorner.com/UploadFile/ddoedens/UseThreadLocals11212005053901AM/UseThreadLocals.aspx

Use ParameterizedThreadStart to pass an object to your thread.

"for later use of the methods it provides."

Using a class that contains method to execute on new thread and other data and methods, you can gain access from your thread to Data and methods from the new thread.

But ... if your execute a method from the class, you are executing on current thread.

To execute the method on the new thread needs some Thread syncronization.

System.Windows.Forms.Control.BeginInvoke do it, the Control thread is waiting until a request arrives.

WaitHandle class can help you.

There's a lot of jargon around threading, But it boils down something pretty simple.

For a simple program, you have one point of execution flowing from point a to b, one line at a time. Programming 101, right?

Ok, for multithreading, You now have more then one point of execution in your program. So, point 1 can be in one part of your program, and point 2 can be someplace else.

It's all the same memory, data and code, but you have more then one thing happening at a time. So, you can think, what happens of both points enter a loop at the same time, what do you think would happen? So techniques were created to keep that kind of issue either from happening, or to speed up some kind of process. (counting a value vs. say, networking.)

That's all it really is. It can be tricky to manage, and and it's easy to get lost in the jargon and theory, but keep this in mind and it will be much simpler.

There are other exceptions to the rule as always, but this is the basics of it.

If the method that you run in a thread resides in a custom class you can have members of this class to hold the parameters.

public class Foo
{
   object parameter1;
   object parameter2;

   public void ThreadMethod()
   {
       ...
   }
}

Sorry to duplicate some previous work, but the OP said

What I actually want to do is to instanciate an object in a new thread for later use of the methods it provides.

Let me interpret that as:

What I actually want to do is have a new thread instantiate an object so that later I can use that object's methods.

Pray correct me if I've missed the mark. Here's the example:

namespace  silly
{
    public static class Program
    {
        //declared volatile to make sure the object is in a consistent state
        //between thread usages -- For thread safety.
        public static volatile Object_w_Methods _method_provider = null;
        static void Main(string[] args)
        {
            //right now, _method_provider is null.
            System.Threading.Thread _creator_thread = new System.Threading.Thread(
                new System.Threading.ThreadStart(Create_Object));
            _creator_thread.Name = "Thread for creation of object";
            _creator_thread.Start();

            //here I can do other work while _method_provider is created.
            System.Threading.Thread.Sleep(256);

            _creator_thread.Join();

            //by now, the other thread has created the _method_provider
            //so we can use his methods in this thread, and any other thread!

            System.Console.WriteLine("I got the name!!  It is: `" + 
                _method_provider.Get_Name(1) + "'");

            System.Console.WriteLine("Press any key to exit...");
            System.Console.ReadKey(true);

        }
        static void Create_Object()
        {
            System.Threading.Thread.Sleep(512);
            _method_provider = new Object_w_Methods();
        }
    }
    public class Object_w_Methods
    {
        //Synchronize because it will probably be used by multiple threads,
        //even though the current implementation is thread safe.
        [System.Runtime.CompilerServices.MethodImpl( 
            System.Runtime.CompilerServices.MethodImplOptions.Synchronized)]
        public string Get_Name(int id)
        {
            switch (id)
            {
                case 1:
                    return "one is the name";
                case 2:
                    return "two is the one you want";
                default:
                    return "supply the correct ID.";
}}}}

Just like to elaborate on a previous answer. To get back to the problem, objects and memory space are shared by all threads. So they are always shared, but I am assuming you want to do so safely and work with results created by another thread.

Firstly try one of the trusted C# patterns. Async Patterns There are set patterns to work with, that do transmit basic messages and data between threads. Usually the one threat completes after it computes the results!

Life threats: Nothing is fool proof when going asynchronous and sharing data on life threats. So basically keep it as simple as possible if you do need to go this route and try follow known patterns.

So now I just like to elaborate why some of the known patters have a certain structure:

Eventargs: where you create a deepcopy of the objects before passing it. (It is not foolproof because certain references might still be shared . ) Passing results with basic types like int floats, etc, These can be created on a constructor and made immutable.

Atomic key words one these types, or create monitors etc.. Stick to one thread reads the other writes.

Assuming you have complex data you like to work with on two threads simultaneously a completely different ways to solve this , which I have not yet tested: You could store results in database and let the other executable read it. ( There locks occur on a row level but you can try again or change the SQL code and at least you will get reported deadlocks that can be solved with good design, not just hanging software!!) I would only do this if it actually makes sense to store the data in a database for other reasons.

Another way that helps is to program F# . There objects and all types are immutable by default/ So your objects you want to share should have a constructor and no methods allow the object to get changed or basic types to get incremented. So you create them and then they don't change! So they are non mutable after that. Makes locking them and working with them in parallel so much easier. Don't go crazy with this in C# classes because others might follow this "convention' and most things like Lists were just not designed to be immutable in C# ( readonly is not the same as immutable, const is but it is very limiting). Immutable versus readonly