Question

How would you send/pass instance references to a new task?

Let’s say I’ve got this:

    public BlockingCollection<string> blockingCollection = new BlockingCollection<string>();
    textBox_txt.Text = "Result: ";
    public Task t = Task.Factory.StartNew(() =>
    {
        foreach (string value in *???1*.blockingCollection.GetConsumingEnumerable())
        {
            *???1*.blockingCollection.Take() 
            [...bla...]
            *???2*.Invoke(new updateTextBox_txtCallback(*???2*.updatetextBox_txt)
                          , new object[] { "THE RESULT!\r\n" });
        }                
    });

I’m guessing that somewhere in here StartNew(() => I have to pass the references to the blockingContent and to the textBox. I’ve looked around but couldn’t figure out the syntax. (it’s quite hairy)

Help, please.

[Edit] So, if I call a static object from withing the Task, it obviously works; but I need the task to work with instances; namely the blockingCollection and the updateTextBox_txtCallback Invoke.

Answer 1

I reproduced your problem, with a workaround below. The problem is that you are using the Task as a field in your class so it can only refer to static members, as the instance hasn’t been constructed until the constructor is run (the field initializers are called before the class is initialized).
From the C# specification (10.5.5.2):

A variable initializer for an instance
field cannot reference the instance
being created. Thus, it is a
compile-time error to reference this
in a variable initializer, as it is a
compile-time error for a variable
initializer to reference any instance
member through a simple-name. In the
example class A { int x = 1; int y =
x + 1; // Error, reference to
instance member of this } the variable
initializer for y results in a
compile-time error because it
references a member of the instance
being created.

Basically you have two options:

1. Initialize your Task variable in the
   constructor
2. Use a method instead for retrieval

Example:

public class Foo
{
    public string myProperty = "foobar";
    public Task t;

    public Foo()
    {
        t = Task.Factory.StartNew(() =>
        {
            myProperty = "test";

        });
    }

    //THIS won't compile
    //public Task t = Task.Factory.StartNew(() =>
    //{
    //    myProperty = "test";

    //});

    public Task GetTask()
    {
        Task t = Task.Factory.StartNew(() =>
        {
            myProperty = "test";

        });
        return t;
    }
}