Events & postbacks

[=?Utf-8?B?QW50?=]

Hi,

I am using a sqlCommand object to run a SP. The SP returns an output
parameter that I retrieve the value of, & display.
I want to use the StatementComple ted event of the command obj. to handle
this output param through the sender object after the command completes.

When I try to access this sender object (cast to a command object) & then
reference the output parm, I get an error:
"Object reference not set to an object"
indicating that the command object has probably lost its reference in the
post back.

How can I handle an event over a Postback?

Many thanks for any help on this. I'm really stuck
Ant

[Michael Nemtsev [MVP]]

Re: Events & postbacks

Hello Ant,

Could your show the short but working code demonstrating the problem?

---
WBR,
Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour

"The greatest danger for most of us is not that our aim is too high and we
miss it, but that it is too low and we reach it" (c) Michelangelo


AHi,
A>
AI am using a sqlCommand object to run a SP. The SP returns an output
Aparameter that I retrieve the value of, & display. I want to use the
AStatementCompl eted event of the command obj. to handle this output
Aparam through the sender object after the command completes.
A>
AWhen I try to access this sender object (cast to a command object) &
Athen
Areference the output parm, I get an error:
A"Object reference not set to an object"
Aindicating that the command object has probably lost its reference in
Athe
Apost back.
AHow can I handle an event over a Postback?
A>
AMany thanks for any help on this. I'm really stuck Ant
A>

[=?Utf-8?B?QW50?=]

Re: Events & postbacks

Hi Michael,
I haven't included the command object set up but I have given it an OP param
& tested it by not using a statement complete event & it returns a value fine
after ExecuteNonQuery . It's only when I try to retrieve it in the event
handler via the event object (as below) that I get the error.

Thanks very much for helping out here

Ant

try
{
connection.Open ();

// execute the SP
commandBackup.E xecuteNonQuery( );

}
catch (Exception ex)
{ // exception handling here }

finally
{ connection.Clos e(); }


void commandBackup_S tatementComplet ed(object sender,
StatementComple tedEventArgs e)
{
// retrieving the command object fromn the sender param of the event
SqlCommand commandResult = ((SqlCommand)se nder);

// !! GET ERROR HERE when trying to access the param value

// retrieve the value of the output parm
string resultString =
commandResult.P arameters["@ResultStr ing"].Value.ToString ();

textboxComplete d.Text = resultString;
}




"Michael Nemtsev [MVP]" wrote:

Hello Ant,
>
Could your show the short but working code demonstrating the problem?
>
---
WBR,
Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour
>
"The greatest danger for most of us is not that our aim is too high and we
miss it, but that it is too low and we reach it" (c) Michelangelo
>
>
AHi,
A>
AI am using a sqlCommand object to run a SP. The SP returns an output
Aparameter that I retrieve the value of, & display. I want to use the
AStatementCompl eted event of the command obj. to handle this output
Aparam through the sender object after the command completes.
A>
AWhen I try to access this sender object (cast to a command object) &
Athen
Areference the output parm, I get an error:
A"Object reference not set to an object"
Aindicating that the command object has probably lost its reference in
Athe
Apost back.
AHow can I handle an event over a Postback?
A>
AMany thanks for any help on this. I'm really stuck Ant
A>
>
>
>

[bruce barker]

Re: Events & postbacks

if you want to use asynchronous events on a web page, the request has to
wait for the events to finish beofre t can send back the response.
otherwise when the event completes there is no request object.

to handle this asynchronous tasks where added to the page. the page will
wait (but free the thread) for the async tasks to complete before doing
prerender.

-- bruce (sqlwork.com)

Ant wrote:

Hi Michael,
I haven't included the command object set up but I have given it an OP param
& tested it by not using a statement complete event & it returns a value fine
after ExecuteNonQuery . It's only when I try to retrieve it in the event
handler via the event object (as below) that I get the error.
>
Thanks very much for helping out here
>
Ant
>
try
{
connection.Open ();
>
// execute the SP
commandBackup.E xecuteNonQuery( );
>
}
catch (Exception ex)
{ // exception handling here }
>
finally
{ connection.Clos e(); }
>
>
void commandBackup_S tatementComplet ed(object sender,
StatementComple tedEventArgs e)
{
// retrieving the command object fromn the sender param of the event
SqlCommand commandResult = ((SqlCommand)se nder);
>
// !! GET ERROR HERE when trying to access the param value
>
// retrieve the value of the output parm
string resultString =
commandResult.P arameters["@ResultStr ing"].Value.ToString ();
>
textboxComplete d.Text = resultString;
}
>
>
>
>
"Michael Nemtsev [MVP]" wrote:
>

>Hello Ant,
>>
>Could your show the short but working code demonstrating the problem?
>>
>---
>WBR,
>Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour
>>
>"The greatest danger for most of us is not that our aim is too high and we
>miss it, but that it is too low and we reach it" (c) Michelangelo
>>
>>
>AHi,
>A>
>AI am using a sqlCommand object to run a SP. The SP returns an output
>Aparameter that I retrieve the value of, & display. I want to use the
>AStatementComp leted event of the command obj. to handle this output
>Aparam through the sender object after the command completes.
>A>
>AWhen I try to access this sender object (cast to a command object) &
>Athen
>Areference the output parm, I get an error:
>A"Object reference not set to an object"
>Aindicating that the command object has probably lost its reference in
>Athe
>Apost back.
>AHow can I handle an event over a Postback?
>A>
>AMany thanks for any help on this. I'm really stuck Ant
>A>
>>
>>
>>

[=?Utf-8?B?QW50?=]

Re: Events & postbacks

Hi Bruce,

Thanks very much for clarifying that for me. Is this something that is not
normally done in ASP.NET? (The use of ADO related events)

If it is, how could this be done

Many thanks

Ant

"bruce barker" wrote:

if you want to use asynchronous events on a web page, the request has to
wait for the events to finish beofre t can send back the response.
otherwise when the event completes there is no request object.
>
to handle this asynchronous tasks where added to the page. the page will
wait (but free the thread) for the async tasks to complete before doing
prerender.
>
-- bruce (sqlwork.com)
>
Ant wrote:

Hi Michael,
I haven't included the command object set up but I have given it an OP param
& tested it by not using a statement complete event & it returns a value fine
after ExecuteNonQuery . It's only when I try to retrieve it in the event
handler via the event object (as below) that I get the error.

Thanks very much for helping out here

Ant

try
{
connection.Open ();

// execute the SP
commandBackup.E xecuteNonQuery( );

}
catch (Exception ex)
{ // exception handling here }

finally
{ connection.Clos e(); }


void commandBackup_S tatementComplet ed(object sender,
StatementComple tedEventArgs e)
{
// retrieving the command object fromn the sender param of the event
SqlCommand commandResult = ((SqlCommand)se nder);

// !! GET ERROR HERE when trying to access the param value

// retrieve the value of the output parm
string resultString =
commandResult.P arameters["@ResultStr ing"].Value.ToString ();

textboxComplete d.Text = resultString;
}




"Michael Nemtsev [MVP]" wrote:

Hello Ant,
>
Could your show the short but working code demonstrating the problem?
>
---
WBR,
Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour
>
"The greatest danger for most of us is not that our aim is too high and we
miss it, but that it is too low and we reach it" (c) Michelangelo
>
>
AHi,
A>
AI am using a sqlCommand object to run a SP. The SP returns an output
Aparameter that I retrieve the value of, & display. I want to use the
AStatementCompl eted event of the command obj. to handle this output
Aparam through the sender object after the command completes.
A>
AWhen I try to access this sender object (cast to a command object) &
Athen
Areference the output parm, I get an error:
A"Object reference not set to an object"
Aindicating that the command object has probably lost its reference in
Athe
Apost back.
AHow can I handle an event over a Postback?
A>
AMany thanks for any help on this. I'm really stuck Ant
A>
>
>
>

>

[Michael Nemtsev [MVP]]

Re: Events & postbacks

Hello Ant,

Keep your results in session or cache
There is no standard way to inform asp.net from the changes on server except
the polling server

---
WBR,
Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour

"The greatest danger for most of us is not that our aim is too high and we
miss it, but that it is too low and we reach it" (c) Michelangelo


AHi Bruce,
A>
AThanks very much for clarifying that for me. Is this something that
Ais not normally done in ASP.NET? (The use of ADO related events)
A>
AIf it is, how could this be done
A>
AMany thanks
A>
AAnt
A>
A"bruce barker" wrote:
A>

>if you want to use asynchronous events on a web page, the request has
>to wait for the events to finish beofre t can send back the response.
>otherwise when the event completes there is no request object.
>>
>to handle this asynchronous tasks where added to the page. the page
>will wait (but free the thread) for the async tasks to complete
>before doing prerender.
>>
>-- bruce (sqlwork.com)
>>
>Ant wrote:
>>

>>Hi Michael,
>>I haven't included the command object set up but I have given it an
>>OP param
>>& tested it by not using a statement complete event & it returns a
>>value fine
>>after ExecuteNonQuery . It's only when I try to retrieve it in the
>>event
>>handler via the event object (as below) that I get the error.
>>Thanks very much for helping out here
>>>
>>Ant
>>>
>>try
>>{
>>connection.Op en();
>>// execute the SP
>>commandBackup .ExecuteNonQuer y();
>>}
>>catch (Exception ex)
>>{ // exception handling here }
>>finally
>>{ connection.Clos e(); }
>>void commandBackup_S tatementComplet ed(object sender,
>>StatementComp letedEventArgs e)
>>{
>>// retrieving the command object fromn the sender param of the event
>>SqlCommand commandResult = ((SqlCommand)se nder);
>>// !! GET ERROR HERE when trying to access the param value
>>>
>>// retrieve the value of the output parm
>>string resultString =
>>commandResult .Parameters["@ResultStr ing"].Value.ToString ();
>>textboxComple ted.Text = resultString;
>>}
>>"Michael Nemtsev [MVP]" wrote:
>>>
>>>Hello Ant,
>>>>
>>>Could your show the short but working code demonstrating the
>>>problem?
>>>>
>>>---
>>>WBR,
>>>Michael Nemtsev [.NET/C# MVP] :: blog:
>>>http://spaces.live.com/laflour
>>>"The greatest danger for most of us is not that our aim is too high
>>>and we miss it, but that it is too low and we reach it" (c)
>>>Michelange lo
>>>>
>>>AHi,
>>>A>
>>>AI am using a sqlCommand object to run a SP. The SP returns an
>>>output
>>>Aparameter that I retrieve the value of, & display. I want to use
>>>the
>>>AStatementCo mpleted event of the command obj. to handle this
>>>output
>>>Aparam through the sender object after the command completes.
>>>A>
>>>AWhen I try to access this sender object (cast to a command
>>>object) &
>>>Athen
>>>Areference the output parm, I get an error:
>>>A"Object reference not set to an object"
>>>Aindicatin g that the command object has probably lost its
>>>reference in
>>>Athe
>>>Apost back.
>>>AHow can I handle an event over a Postback?
>>>A>
>>>AMany thanks for any help on this. I'm really stuck Ant
>>>A>