Threading on Functions returning values

  • Thread starter Thread starter A.K.Seerajdeen
  • Start date Start date
A

A.K.Seerajdeen

Hi All,

I am a developer in .Net 2005, I am facing a problem in Multithreading
concept. The problem is, I have a function which returns a value of string
type and also carries some parameters(Arguments) and I am calling that
function in a button click. When ever I call the fuction the GUI gets hanged
Up. So, I want to apply threading concept on it since that function parses
number of webpages, it takes lot of time and the GUI gets struck up mean
while, it has become a very big problem.

I hope, have understood the problem, Please anyone help me solving this
problem, any sample code or any explaination regarding this would me a great
help for me.

Thanks In advance to all, I hope this forum would be a great help for me,
since I am new to this forum.


Thanking You,


With Regards,
A.K.Seerajdeen,
Jr. Software Programmer,
Nanna Computers (Vizag),
Tel: +919885444639,
(e-mail address removed).

(This electronic message contains information from Nanna Computers, which
may be privileged or confidential. The information is for the intended
individual(s) or entity named above. If you are not the intended recipient
be aware that any copying, disclosing, distribution or use of the above
email and/or its attachments is prohibited and is illegal. If you have
received this electronic message in error, please notify us by telephone or
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Ivar,

How do You call Control.Invoke on a method that has a return type other than
void?

Best regards,

Benny
 
you must declare delegate before, then you can call delegate.

like:

private delegate OnCompletedOnUIDelegate void (string value)

class xxx .....

// Assume that this is called from not UI thread
private void OnCompleted(string value)
{
this.Invoke(new OnCompletedOnUIDelegate
(this.OnCompletedOnUIThread),new object[]{value});
}

// This is called on UI thread.
private void OnCompletedOnUIThread(string value)
{
}
 
you must declare delegate before, then you can call delegate.

like:

private delegate OnCompletedOnUIDelegate void (string value)
Click to expand...

Except that he specifically asked about calling delegates that have a
return type other than void. So I'm not sure your example is the best
one. :)

As far as the actual answer goes:

Control.Invoke() returns an object. This is the return value of the
delegate being called. If the return value isn't a reference type (ie,
not derived from Object), that's not a problem. The value type is simply
boxed and returned as an Object reference. You can then assign this back
to the expected value type and the return value will be unboxed.

So, it works exactly as you'd expect. Just have your delegate return a
value, and then assign the return value of Control.Invoke() to whatever
you need it to be assigned to (or use it in an expression however you need
it, whatever's appropriate).

Pete
 
Hi Mr.Peter,

Thank you for responding to my query. I could able to understand the =
explaination given below by you. I have tried the way which you have =
explained but I am not able to do the coding has you have mentioned =
since lack of idea in delegates. It will be more helpful if you could =
explain me in terms of coding. Please do not mind and please help me out =
of this problem.

Thanking You,

With Regards,
A.K.Seerajdeen,
Emp ID: NGV33051,
Jr. Software Programmer,
Nanna Computers (Vizag),
Tel: +919885444639,
(e-mail address removed)
 
Hi Mr.Peter,

Thank you for responding to my query. I could able to understand the =
explaination given below by you. I have tried the way which you have =
explained but I am not able to do the coding has you have mentioned =
since lack of idea in delegates. It will be more helpful if you could =
explain me in terms of coding.
Click to expand...

As an example:

delegate string MyDelegate();

void InvokingMethod()
{
string strT;

strT = (string)this.Invoke((MyDelegate)InvokedMethod);
}

string InvokedMethod()
{
return "This is a test string";
}

In other words, it works just like calling a method directly, in that when
the delegate returns a value, so too does the Invoke() method. Just cast
the return value from Invoke() to whatever you need, and as long as the
cast matches the actual return type of the invoked method, it will work
fine.

If the above does not solve the issue, I recommend that you read the MSDN
documentation on delegates as well as the Control.Invoke() method. If you
still have questions, please feel free to post them, but do make sure that
the questions are specific enough to be able to answered in a
straight-forward way. It would be especially useful if you phrase the
question in terms of what in the documentation you are having trouble
understanding.

Pete
 
Hi Mr.Peter,

Thank you for responding to my request of coding. I am very glad and happy
to add in this forum. People like you are very Important for this forum.
From the below code which you have send me I could able to solve my problem,
Thank very much for this code. I hope I could also help others in the same
way like you did.


Thanking You,

With Regards,
A.K.Seerajdeen,
Emp ID: NGV33051,
Jr. Software Programmer,
Nanna Computers (Vizag),
Tel: +919885444639,
(e-mail address removed).

(This electronic message contains information from Nanna Computers, which
may be privileged or confidential. The information is for the intended
individual(s) or entity named above. If you are not the intended recipient
be aware that any copying, disclosing, distribution or use of the above
email and/or its attachments is prohibited and is illegal. If you have
received this electronic message in error, please notify us by telephone or
email (to the numbers or address above) immediately. This e-mail is not
un-solicited e-mail under the relevant regulations.)




As an example:

delegate string MyDelegate();

void InvokingMethod()
{
string strT;

strT = (string)this.Invoke((MyDelegate)InvokedMethod);
}

string InvokedMethod()
{
return "This is a test string";
}

In other words, it works just like calling a method directly, in that when
the delegate returns a value, so too does the Invoke() method. Just cast
the return value from Invoke() to whatever you need, and as long as the
cast matches the actual return type of the invoked method, it will work
fine.

If the above does not solve the issue, I recommend that you read the MSDN
documentation on delegates as well as the Control.Invoke() method. If you
still have questions, please feel free to post them, but do make sure that
the questions are specific enough to be able to answered in a
straight-forward way. It would be especially useful if you phrase the
question in terms of what in the documentation you are having trouble
understanding.

Peter..
 
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