Data access with thread

[Edwin]

I want to make a program that retreive data from sql server. Currently, i'm
using sqlDataReader, dataTable and dataGrind. I try to use thread so the
program is not locked during the search task and the user have a control
to stop the search task. In this thread, sqlDataReader search the data from
sql server and pass it to dataTable. The problem came when i try to bind
this dataTable to dataGrid. If I bind the datagrid in new() constructor,
or in form1_load method, i got an error in Form1 (main form) when i execute
the search task. I also try to make an event in thread, so that when the
thread has been finished searching data or search is cancelled, then it raise
an event that pass the dataTable. But when i want to bind this dataTable
to dataGrid, i got an error which tell me that i can't bind my datagrid
with an object from different thread. What is i have to do so that i can
run data access with thread? Is there any other way to get data from server
while still having a control to cancel it? Thanks.

[Phil Weber]

> when I want to bind this dataTable to dataGrid, I got an
> error which tell me that I can't bind my datagrid with an
> object from different thread.

Edwin: See the thread titled, "Threading and the .NET Datagrid" in this
discussion group:
http://news.devx.com/cgi-bin/dnewswe...nical&xrelated
=7680&cmd_related.x=1
---
Phil Weber

[Edwin]

"Phil Weber" <pweber@nospam.fawcette.com> wrote:
> > when I want to bind this dataTable to dataGrid, I got an
> > error which tell me that I can't bind my datagrid with an
> > object from different thread.
>
>Edwin: See the thread titled, "Threading and the .NET Datagrid" in this
>discussion group:
>http://news.devx.com/cgi-bin/dnewswe...nical&xrelated
>=7680&cmd_related.x=1
>---
>Phil Weber
>
>


>Windows forms controls are NOT threadsafe. You'll have to marshall
>calls from a different thread back to the thread that created the
>control. See:

>http://samples.gotdotnet.com/QuickSt.../default.aspx?
>url=/quickstart/howto/doc/WinForms/WinFormsThreadMarshalling.aspx

Thanks. Marshall calls has been solve my problem to bind data from other
thread. But now the thread act just like there is no thread at all. My program
still lock during the search task (but now i can update my datagrid in this
thread). Did I miss something about marshall calls to make it act just like
ordinary thread (release the resource)? I try to make the thread sleep in
search loops, but it still didn't release the resource. I just want to make
user have a control to stop the search task. How suppose i do this task?

[Edwin]

"Edwin" <edwin.arif@chek.com> wrote:
>
>"Phil Weber" <pweber@nospam.fawcette.com> wrote:
>> > when I want to bind this dataTable to dataGrid, I got an
>> > error which tell me that I can't bind my datagrid with an
>> > object from different thread.
>>
>>Edwin: See the thread titled, "Threading and the .NET Datagrid" in this
>>discussion group:
>>http://news.devx.com/cgi-bin/dnewswe...nical&xrelated
>>=7680&cmd_related.x=1
>>---
>>Phil Weber
>>
>>
>
>
>>Windows forms controls are NOT threadsafe. You'll have to marshall
>>calls from a different thread back to the thread that created the
>>control. See:
>
>>http://samples.gotdotnet.com/QuickSt.../default.aspx?
>>url=/quickstart/howto/doc/WinForms/WinFormsThreadMarshalling.aspx
>
>Thanks. Marshall calls has been solve my problem to bind data from other
>thread. But now the thread act just like there is no thread at all. My >program
still lock during the search task (but now i can update my >datagrid in this
thread). Did I miss something about marshall calls to >make it act just like
ordinary thread (release the resource)? I try to >make the thread sleep in
search loops, but it still didn't release the >resource. I just want to make
user have a control to stop the search >task. How suppose i do this task?

I'm looking at microsoft product service control just like phil told. Maybe
there is an answer for me about my problem. I'm a newbie in threading, i
just hope this thread doesn't kill me. Arrggghh... I hate threading.

[Edwin]

"Edwin" <edwin.arif@chek.com> wrote:
>
>"Edwin" <edwin.arif@chek.com> wrote:
>>
>>"Phil Weber" <pweber@nospam.fawcette.com> wrote:
>>> > when I want to bind this dataTable to dataGrid, I got an
>>> > error which tell me that I can't bind my datagrid with an
>>> > object from different thread.
>>>
>>>Edwin: See the thread titled, "Threading and the .NET Datagrid" in this
>>>discussion group:
>>>http://news.devx.com/cgi-bin/dnewswe...nical&xrelated
>>>=7680&cmd_related.x=1
>>>---
>>>Phil Weber
>>>
>>>
>>
>>
>>>Windows forms controls are NOT threadsafe. You'll have to marshall
>>>calls from a different thread back to the thread that created the
>>>control. See:
>>
>>>http://samples.gotdotnet.com/QuickSt.../default.aspx?
>>>url=/quickstart/howto/doc/WinForms/WinFormsThreadMarshalling.aspx
>>
>>Thanks. Marshall calls has been solve my problem to bind data from other
>>thread. But now the thread act just like there is no thread at all. My
>program
>still lock during the search task (but now i can update my >datagrid in
this
>thread). Did I miss something about marshall calls to >make it act just
like
>ordinary thread (release the resource)? I try to >make the thread sleep
in
>search loops, but it still didn't release the >resource. I just want to
make
>user have a control to stop the search >task. How suppose i do this task?
>
>I'm looking at microsoft product service control just like phil told. Maybe
>there is an answer for me about my problem. I'm a newbie in threading, i
>just hope this thread doesn't kill me. Arrggghh... I hate threading.


Thanks again... that article is really helping me with threading. But now
new problem is coming. I already try to search it from framework sdk quickstart
and documentation, but i still can't find any reference how i can solve this
problem. Just like i said before, i want to make a program that search database
while user still have a control to cancel the operation. The problem is I
can't just stop closing my dataReader, looks like it always read through
the database in server until it finished searching. This is the code looks
like :

....
dim myDataTable as DataTable
dim myDataReader as DataReader
dim isCancelled as boolean
Dim CallDataBindToDataGrid As New MethodInvoker(AddressOf _ Me.DataBindToDataGrid)

public sub QueryDataBase(){
.....
dim strsql as string = "SELECT * FROM Table"
Dim cmd As New SqlCommand(strSQL, myConnection)
myDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)
While isCancelled = False AndAlso myDataReader.Read = True
'fill myDataTable
......
end while
Me.BeginInvoke(CallDataBindToDataGrid)
}

Public Sub DataBindToDataGrid()
DataGrid1.DataSource = myDataTable
DataGrid1.Update()
myDataReader.Close() 'This is where the problem happened
myDataReader = Nothing
myDataTable = Nothing
End Sub

....

If user click button btnCancel, then isCancelled = true (out of loop). But
when the program reach code "myDataReader.close()", it just like we still
have to wait until the search is completed. Of course with a lot of data
in database, it really consume a lot of time. If i didn't use myDataReader.close(),
the program runs just like i want it to. But i only can search one time,
because when i want to search again, i got an error that tell me dataReader
is open. How can i use this dataReader the way i want it to? Or maybe there
is another way to retreive data from database and we can just cancel the
operation if we want it to? Thanks...