C# / Winforms multithreading

[Ludwig Wittgenstein]

Hello, all.

I'm developing an application that has a listview of records
(pulled from the database) and a preview pane. Basically, when the
user clicks on a record in the listview the preview pane gets
populated with additional information about the record. Each record
also have a variable number of pictures. What I want to do is have
the application fetch the pictures from the database in a separate
thread. What is the best way to do this? I tried creating a Thread
object every time and invoke a method, however If I scroll really
fast in the listview the application crashes and I cannot debug it. Is
there a specific section that I should lock() when the thread is
started? Also how do i guarantee that the last record selected is that
one that will have the most recent started thread's data?
Thanks,

[=?Utf-8?B?UGV0ZXIgQnJvbWJlcmcgW0MjIE1WUF0=?=]

It sounds to me that most likely your issue revolves around attempting to
update a control on the UI (main) thread from another thread. You need to use
a delegate to do this.

Here is a nice little reusable pattern that you can look at:
delegate void SetValueDelegate(Object obj, Object val, Object[] index);

public void SetControlProperty(Control ctrl, String propName, Object val)
{
PropertyInfo propInfo = ctrl.GetType().GetProperty(propName);
Delegate dgtSetValue = new SetValueDelegate(propInfo.SetValue);
ctrl.Invoke(dgtSetValue, new Object[3] { ctrl, val, /*index*/ null });
}

// Usage: SetControlProperty(label1, "Text", myString);
--
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"Ludwig Wittgenstein" wrote:

Hello, all.

I'm developing an application that has a listview of records
(pulled from the database) and a preview pane. Basically, when the
user clicks on a record in the listview the preview pane gets
populated with additional information about the record. Each record
also have a variable number of pictures. What I want to do is have
the application fetch the pictures from the database in a separate
thread. What is the best way to do this? I tried creating a Thread
object every time and invoke a method, however If I scroll really
fast in the listview the application crashes and I cannot debug it. Is
there a specific section that I should lock() when the thread is
started? Also how do i guarantee that the last record selected is that
one that will have the most recent started thread's data?
Thanks,

[Didier Bolf]

to avoid useless call to the database when scrolling in the ListView,
you should use a Delayed event handling mechanism :
http://www.vbinfozine.com/a_deh.shtml

Didier

"Ludwig Wittgenstein" <se********@hotmail.comwrote in message
news:11**********************@z28g2000prd.googlegr oups.com...

Hello, all.

I'm developing an application that has a listview of records
(pulled from the database) and a preview pane. Basically, when the
user clicks on a record in the listview the preview pane gets
populated with additional information about the record. Each record
also have a variable number of pictures. What I want to do is have
the application fetch the pictures from the database in a separate
thread. What is the best way to do this? I tried creating a Thread
object every time and invoke a method, however If I scroll really
fast in the listview the application crashes and I cannot debug it. Is
there a specific section that I should lock() when the thread is
started? Also how do i guarantee that the last record selected is that
one that will have the most recent started thread's data?
Thanks,

[verbiest]

On 19 jun, 13:44, Peter Bromberg [C# MVP]
<[e-mail]:

It sounds to me that most likely your issue revolves around attempting to
update a control on the UI (main) thread from another thread. You need to use
a delegate to do this.

Here is a nice little reusable pattern that you can look at:

delegate void SetValueDelegate(Object obj, Object val, Object[] index);

public void SetControlProperty(Control ctrl, String propName, Object val)
{
PropertyInfo propInfo = ctrl.GetType().GetProperty(propName);
Delegate dgtSetValue = new SetValueDelegate(propInfo.SetValue);
ctrl.Invoke(dgtSetValue, new Object[3] { ctrl, val, /*index*/ null });

}

// Usage: SetControlProperty(label1, "Text", myString);

--
Site: http://www.eggheadcafe.com
UnBlog: http://petesbloggerama.blogspot.com
Short urls & more: http://ittyurl.net

"Ludwig Wittgenstein" wrote:

Hello, all.

I'm developing an application that has a listview of records
(pulled from the database) and a preview pane. Basically, when the
user clicks on a record in the listview the preview pane gets
populated with additional information about the record. Each record
also have a variable number of pictures. What I want to do is have
the application fetch the pictures from the database in a separate
thread. What is the best way to do this? I tried creating a Thread
object every time andinvokea method, however If I scroll really
fast in the listview the application crashes and I cannot debug it. Is
there a specific section that I should lock() when the thread is
started? Also how do i guarantee that the last record selected is that
one that will have the most recent started thread's data?

Thanks,- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

If you can, it's better to use BeginInvoke() instead of Invoke().
Read more about it (and other threading issues) here:
http://kristofverbiest.blogspot.com/...gininvoke.html