Unable to delete row

[travlintom]

Hi. I'm new to VB.net and am used to working with recordsets (much
easier). I have a datagrid that, when the user double clicks on a row,
I am giving them a chance to delete it. I thought this would be simple
but it's taking me forever. I am getting an error when I try to delete
the record. I can't figure out what I'm doing wrong.
The error is "Object reference not set to an instance of an object".
None of the incredibly overpriced books I have seem to be of any help.
Someone's knowledge would be greatly appreciated.
Private Sub dgProjItems_Dou bleClick(ByVal sender As Object, ByVal e As
System.EventArg s) Handles dgProjItems.Dou bleClick
Dim CurItemID As String
CurItemID = dgProjItems.Ite m(dgProjItems.C urrentRowIndex( ), 0)

Dim strConnectionSt ring As String = _
"Provider=Micro soft.Jet.OLEDB. 4.0;" & _
"Data
Source=C:\Datab ases\NewEstimat e.mdb;"
Dim cn As New OleDbConnection (strConnectionS tring)
Dim strSQLl As String = "Select * from ProjectsItems Where
ItemID = '" & CurItemID & "'"
Dim objCommand1 As New OleDbCommand(st rSQLl, cn)
Dim da As New OleDbDataAdapte r(objCommand1)
Dim ds As New DataSet

Try
cn.Open()

Dim cb As New OleDb.OleDbComm andBuilder(da)

ds.Tables("Proj ectItems").Rows (0).Delete() 'error here
da.Update(ds, "ProjectIte ms")

Me.dgProjItems. DataSource = ds.Tables("Proj ectItems")

Catch OleDbExceptionE rr As OleDb.OleDbExce ption
MessageBox.Show (OleDbException Err.Message, "Access SQL")
End Try
End Sub

[Chris]

tr********@yaho o.com wrote:

Hi. I'm new to VB.net and am used to working with recordsets (much
easier). I have a datagrid that, when the user double clicks on a row,
I am giving them a chance to delete it. I thought this would be simple
but it's taking me forever. I am getting an error when I try to delete
the record. I can't figure out what I'm doing wrong.
The error is "Object reference not set to an instance of an object".
None of the incredibly overpriced books I have seem to be of any help.
Someone's knowledge would be greatly appreciated.
Private Sub dgProjItems_Dou bleClick(ByVal sender As Object, ByVal e As
System.EventArg s) Handles dgProjItems.Dou bleClick
Dim CurItemID As String
CurItemID = dgProjItems.Ite m(dgProjItems.C urrentRowIndex( ), 0)

Dim strConnectionSt ring As String = _
"Provider=Micro soft.Jet.OLEDB. 4.0;" & _
"Data
Source=C:\Datab ases\NewEstimat e.mdb;"
Dim cn As New OleDbConnection (strConnectionS tring)
Dim strSQLl As String = "Select * from ProjectsItems Where
ItemID = '" & CurItemID & "'"
Dim objCommand1 As New OleDbCommand(st rSQLl, cn)
Dim da As New OleDbDataAdapte r(objCommand1)
Dim ds As New DataSet

Try
cn.Open()

Dim cb As New OleDb.OleDbComm andBuilder(da)

ds.Tables("Proj ectItems").Rows (0).Delete() 'error here
da.Update(ds, "ProjectIte ms")

Me.dgProjItems. DataSource = ds.Tables("Proj ectItems")

Catch OleDbExceptionE rr As OleDb.OleDbExce ption
MessageBox.Show (OleDbException Err.Message, "Access SQL")
End Try
End Sub

"Object reference not set to an instance of an object"

This error means that an object you are trying to do an operation
against does not exist (is nothing). so figure out which object is empty.

dim DT as datatable = ds.Tables("Proj ectItems")
dim DR as datarow = DT.Rows(0)
DR.Delete()

My guess is that your datatable isn't named ProjectItems so that is
returning nothing.

Chris

[Scott Swigart]

Your code isn't going to work because on one line you create a new empty
dataset:

Dim ds As New DataSet

And then on another line, you are attempting to delete from this empty
dataset:

ds.Tables("Proj ectItems").Rows (0).Delete() 'error here

You're never calling Fill on your OleDbDataAdapte r to fill this dataset so
that you can delete the row.
"tr********@yah oo.com" wrote:

Hi. I'm new to VB.net and am used to working with recordsets (much
easier). I have a datagrid that, when the user double clicks on a row,
I am giving them a chance to delete it. I thought this would be simple
but it's taking me forever. I am getting an error when I try to delete
the record. I can't figure out what I'm doing wrong.
The error is "Object reference not set to an instance of an object".
None of the incredibly overpriced books I have seem to be of any help.
Someone's knowledge would be greatly appreciated.
Private Sub dgProjItems_Dou bleClick(ByVal sender As Object, ByVal e As
System.EventArg s) Handles dgProjItems.Dou bleClick
Dim CurItemID As String
CurItemID = dgProjItems.Ite m(dgProjItems.C urrentRowIndex( ), 0)

Dim strConnectionSt ring As String = _
"Provider=Micro soft.Jet.OLEDB. 4.0;" & _
"Data
Source=C:\Datab ases\NewEstimat e.mdb;"
Dim cn As New OleDbConnection (strConnectionS tring)
Dim strSQLl As String = "Select * from ProjectsItems Where
ItemID = '" & CurItemID & "'"
Dim objCommand1 As New OleDbCommand(st rSQLl, cn)
Dim da As New OleDbDataAdapte r(objCommand1)
Dim ds As New DataSet

Try
cn.Open()

Dim cb As New OleDb.OleDbComm andBuilder(da)

ds.Tables("Proj ectItems").Rows (0).Delete() 'error here
da.Update(ds, "ProjectIte ms")

Me.dgProjItems. DataSource = ds.Tables("Proj ectItems")

Catch OleDbExceptionE rr As OleDb.OleDbExce ption
MessageBox.Show (OleDbException Err.Message, "Access SQL")
End Try
End Sub

[travlintom]

Thank you both for your quick reply.
Scott........I added the fill method and now get the error "An
unhandled exception of type 'System.Data.Ol eDb.OleDbExcept ion' occurred
in system.data.dll "

Here's the revised code:

Dim strSQLl As String = "Select * from ProjectItems Where ItemID = '" &
CurItemID & "'"
Dim objCommand1 As New OleDbCommand(st rSQLl, cn)
Dim da As New OleDbDataAdapte r(objCommand1)
Dim ds As New DataSet
da.Fill(ds, "ProjectIte ms")
Try
cn.Open()

Dim cb As New OleDb.OleDbComm andBuilder(da)

ds.Tables("Proj ectItems").Rows (0).Delete()

da.Update(ds, "ProjectIte ms")

Me.dgProjItems. DataSource = ds.Tables("Proj ectItems")

Catch OleDbExceptionE rr As OleDb.OleDbExce ption
MessageBox.Show (OleDbException Err.Message, "Access SQL")
End Try

Chris........Th e table name is correct. Thanks.

[Chris]

tr********@yaho o.com wrote:

Thank you both for your quick reply.
Scott........I added the fill method and now get the error "An
unhandled exception of type 'System.Data.Ol eDb.OleDbExcept ion' occurred
in system.data.dll "

Here's the revised code:

Dim strSQLl As String = "Select * from ProjectItems Where ItemID = '" &
CurItemID & "'"
Dim objCommand1 As New OleDbCommand(st rSQLl, cn)
Dim da As New OleDbDataAdapte r(objCommand1)
Dim ds As New DataSet
da.Fill(ds, "ProjectIte ms")
Try
cn.Open()

Dim cb As New OleDb.OleDbComm andBuilder(da)

ds.Tables("Proj ectItems").Rows (0).Delete()

da.Update(ds, "ProjectIte ms")

Me.dgProjItems. DataSource = ds.Tables("Proj ectItems")

Catch OleDbExceptionE rr As OleDb.OleDbExce ption
MessageBox.Show (OleDbException Err.Message, "Access SQL")
End Try

Chris........Th e table name is correct. Thanks.

what does oledbexceptione rr.message say? It will give more detail about
what the error is.

Chris

[travlintom]

I ran through all the code. That's the only error I get.

[Cor Ligthert [MVP]]

Travlintom,

At least do you consequently have to close something when you open
something. Closing and opening is in fact not needed for a dataadapter
(however better when you use more tables), because the dataadapter does that
generic for you.

Your block could be this both for the Fill and the Update
Try
open connection
Try
fill or update
Catch error
'do action for the Try or Update
End Try
Catch error
'do action for the Open
Finally
Close connection
End Try

As I wrote, you can not use the open. In Net 2.0 you can than use as well
"using".

I hope this helps,

Cor

[travlintom]

Thanks all. I found the problem. It was actually the SQL statement was
looking for a string when It should have been an integer. I made the
change and it works fine. Thanks for all your help.