callback / delegate? - windows

Question

i have a doubt..
i would like to create a function and it will look like this...
public class A //this is just a class file
{
function dowork()
{
//work 1
INPUT = here in this line it should call a delegate function or raise event etc...
//work 2 using INPUT
}
}
public class B
{
function myfn()
{
A objA = new A();
objA.dowork();
}
}
In the "Class A" we will raise event or so & it will display a windows form to user and then user will input some value & we need to return that value to Class A -> dowork method.... then only we should continue "work 2"
this should also support multi threading... anyone have idea how we can implement this??
thanks :)

Answer 1

You can use ManulResetEvent for this purpose: You run your input form and when it done that form set the event so you can catch it from A.dowork method. While the input in action you run the infinite loop, check event state and process application event to make you app responsible in this time:
public class A //this is just a class file
{
private ManualResetEvent _event;
public void dowork()
{
//work 1
_event = new ManualResetEvent(false);
//INPUT = here in this ...
Worker worker = new Worker();
worker.DoInput(_event);
while(true)
{
if(_event.WaitOne())
break;
Application.DoEvents();
}
//work 2 using INPUT
}
}
class Worker
{
private ManualResetEvent _event;
public void DoInput(ManualResetEvent #event)
{
_event = #event;
// Show input form here.
// When it done, you call: _event.Set();
}
}
Also, I suggest you (if you can) use Async library (it is available as a standalone setup). There you can implement it in much more straightforward way:
public class A //this is just a class file
{
public async void dowork()
{
//work 1
//INPUT = here in this ...
Worker worker = new Worker();
wait worker.DoInput();
//work 2 using INPUT
}
}
class Worker
{
public async void DoInput()
{
InputForm form = new InputForm();
wait form.ShowInput();
}
}
public class B
{
async void myfn()
{
A objA = new A();
wait objA.dowork();
}
}
As you see you just wait while other piece of code get executed without any UI locking and events.
I can provide deeper explanation of how async/wait works here if you need.