Object reference not set to an instance of an object. .......... Error .... Please Help

[Sean]

Hi,

I am facing a problem, and i don't know why the error is being generated.

I am updating a datagrid with an XML file.

My code is

Protected Sub UpdateCommand(ByVal Sender As Object, ByVal E As DataGridCommandEventArgs)
Try
Dim deletekey As String
dgpayer.EditItemIndex = -1
deletekey = dgpayer.DataKeys(CInt(E.Item.ItemIndex))

' these are the 4 new edited values
Dim newpaymentamount As String = (CType(E.Item.FindControl("txtepaymentamount"), TextBox).Text)
Dim newpaymentreference As String = (CType(E.Item.FindControl("txtepaymentreference"), TextBox).Text)
Dim newcomment As String = (CType(E.Item.FindControl("txtecomment"), TextBox).Text)
Dim newdatetime As String = (CType(E.Item.FindControl("txtedatetime"), TextBox).Text)
' Response.Write(newcomment)
'load the XML
Dim doc As New XmlDocument()
doc.Load("c:\Inetpub\wwwroot\Cashier\cashier.xml")

Dim node As XmlElement = doc.SelectSingleNode("cashier/tag[@section=payer-" & lbunique.Text & "']")

' setting the attributes to the xml node to replace the values with the new ones
node.SetAttribute("payment_amount", newpaymentamount)
node.SetAttribute("payment_reference", newpaymentreference)
node.SetAttribute("comment", newcomment)
node.SetAttribute("datetime", newdatetime)

' save the xml
doc.Save("c:\Inetpub\wwwroot\Cashier\cashier.xml")

'display the datagrid
viewgrid()
Catch Exc As Exception
lbError.Text = "Update DataGrid Error: " & Exc.Message
End Try
End Sub

And my XML file is

<?xml version="1.0" standalone="yes"?>
<cashier>
<tag param1="payer-16" param2="Reeves" param3="1" param4="324" payment_amount="123.00" payment_reference="123" comment="asf" datetime="7/8/2003" />
<tag param1="payer-14" param2="Johnny" param3="3" param4="345" payment_amount="113.00" payment_reference="123" comment="asf" datetime="7/8/2003" />
<tag param1="payer-14" param2="Joahns" param3="2" param4="325" payment_amount="135.00" payment_reference="123" comment="asf" datetime="7/8/2003" />
</cashier>

The error is generated why i set the attributes to replace the old values with the new ones.

The error message is 'Object reference not set to an instance of an object.'

Any help is appreciated.

--
Thank You,
Sean

[Chad Tamplin]

The error is thrown because you are not finding any nodes when you call the
following line..

Dim node As XmlElement = doc.SelectSingleNode("cashier/tag[@section=payer-"
& lbunique.Text & "']")

It looks like your XPath query is not correct. I don't see an attribute
called 'section' in your xml.

Chad

"Sean" <nospam@> wrote in message
news:#A**************@TK2MSFTNGP11.phx.gbl...
Hi,

I am facing a problem, and i don't know why the error is being generated.

I am updating a datagrid with an XML file.

My code is

Protected Sub UpdateCommand(ByVal Sender As Object, ByVal E As
DataGridCommandEventArgs)
Try
Dim deletekey As String
dgpayer.EditItemIndex = -1
deletekey = dgpayer.DataKeys(CInt(E.Item.ItemIndex))

' these are the 4 new edited values
Dim newpaymentamount As String =
(CType(E.Item.FindControl("txtepaymentamount"), TextBox).Text)
Dim newpaymentreference As String =
(CType(E.Item.FindControl("txtepaymentreference"), TextBox).Text)
Dim newcomment As String =
(CType(E.Item.FindControl("txtecomment"), TextBox).Text)
Dim newdatetime As String =
(CType(E.Item.FindControl("txtedatetime"), TextBox).Text)
' Response.Write(newcomment)
'load the XML
Dim doc As New XmlDocument()
doc.Load("c:\Inetpub\wwwroot\Cashier\cashier.xml")

Dim node As XmlElement =
doc.SelectSingleNode("cashier/tag[@section=payer-" & lbunique.Text & "']")

' setting the attributes to the xml node to replace the values
with the new ones
node.SetAttribute("payment_amount", newpaymentamount)
node.SetAttribute("payment_reference", newpaymentreference)
node.SetAttribute("comment", newcomment)
node.SetAttribute("datetime", newdatetime)

' save the xml
doc.Save("c:\Inetpub\wwwroot\Cashier\cashier.xml")

'display the datagrid
viewgrid()
Catch Exc As Exception
lbError.Text = "Update DataGrid Error: " & Exc.Message
End Try
End Sub

And my XML file is

<?xml version="1.0" standalone="yes"?>
<cashier>
<tag param1="payer-16" param2="Reeves" param3="1" param4="324"
payment_amount="123.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
<tag param1="payer-14" param2="Johnny" param3="3" param4="345"
payment_amount="113.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
<tag param1="payer-14" param2="Joahns" param3="2" param4="325"
payment_amount="135.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
</cashier>

The error is generated why i set the attributes to replace the old values
with the new ones.

The error message is 'Object reference not set to an instance of an
object.'

Any help is appreciated.

--
Thank You,
Sean

[Shahram Khosraviani]

Sorry,

i did make a change to the xml file.

the xml file is

<?xml version="1.0" standalone="yes"?>
<cashier>
<tag section="work-14" param2="123" param2="NOTARY" param3="7/9/2003 08:00
AM" param5="PENDING" param6="3" param7="1000341" />
<tag Section="payer-14" param2="New York" param2="1" param3="CHECK/MO"
payment_amount="123.00" payment_reference="12" param4="No" comment="asdf"
datetime="7/9/2003" />
</cashier>

phew, it worked.

now, the problem is that there is no unique key in the xml file, so it
replaces the first occurance of the payer attribute.

Should i change the xml file, in order to generate a unique field to each of
the tags, or should i combine the elements in the SelectSingleNode into
'and' statement ?

Just wondering what is the better approach.
Dim node As XmlElement =
doc.SelectSingleNode("cashier/tag[@Section='payerinformation-" &
lbunique.Text & "']")


"Chad Tamplin" <ch**********@cinfin.com> wrote in message
news:e4**************@tk2msftngp13.phx.gbl...

The error is thrown because you are not finding any nodes when you call the following line..

Dim node As XmlElement = doc.SelectSingleNode("cashier/tag[@section=payer-" & lbunique.Text & "']")

It looks like your XPath query is not correct. I don't see an attribute
called 'section' in your xml.

Chad

"Sean" <nospam@> wrote in message
news:#A**************@TK2MSFTNGP11.phx.gbl...
Hi,

I am facing a problem, and i don't know why the error is being generated.

I am updating a datagrid with an XML file.

My code is

Protected Sub UpdateCommand(ByVal Sender As Object, ByVal E As
DataGridCommandEventArgs)
Try
Dim deletekey As String
dgpayer.EditItemIndex = -1
deletekey = dgpayer.DataKeys(CInt(E.Item.ItemIndex))

' these are the 4 new edited values
Dim newpaymentamount As String =
(CType(E.Item.FindControl("txtepaymentamount"), TextBox).Text)
Dim newpaymentreference As String =
(CType(E.Item.FindControl("txtepaymentreference"), TextBox).Text)
Dim newcomment As String =
(CType(E.Item.FindControl("txtecomment"), TextBox).Text)
Dim newdatetime As String =
(CType(E.Item.FindControl("txtedatetime"), TextBox).Text)
' Response.Write(newcomment)
'load the XML
Dim doc As New XmlDocument()
doc.Load("c:\Inetpub\wwwroot\Cashier\cashier.xml")

Dim node As XmlElement =
doc.SelectSingleNode("cashier/tag[@section=payer-" & lbunique.Text & "']")

' setting the attributes to the xml node to replace the values
with the new ones
node.SetAttribute("payment_amount", newpaymentamount)
node.SetAttribute("payment_reference", newpaymentreference)
node.SetAttribute("comment", newcomment)
node.SetAttribute("datetime", newdatetime)

' save the xml
doc.Save("c:\Inetpub\wwwroot\Cashier\cashier.xml")

'display the datagrid
viewgrid()
Catch Exc As Exception
lbError.Text = "Update DataGrid Error: " & Exc.Message
End Try
End Sub

And my XML file is

<?xml version="1.0" standalone="yes"?>
<cashier>
<tag param1="payer-16" param2="Reeves" param3="1" param4="324"
payment_amount="123.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
<tag param1="payer-14" param2="Johnny" param3="3" param4="345"
payment_amount="113.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
<tag param1="payer-14" param2="Joahns" param3="2" param4="325"
payment_amount="135.00" payment_reference="123" comment="asf"
datetime="7/8/2003" />
</cashier>

The error is generated why i set the attributes to replace the old values
with the new ones.

The error message is 'Object reference not set to an instance of an
object.'

Any help is appreciated.

--
Thank You,
Sean