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System.NullReferenceException: Object reference not set to an inst

P: n/a
I'm loading an Array below but getting the error "Object reference not set to
an instance saying 'ItemNumber = CType(Args.Item.FindControl("ItemNumber"),
TextBox).Text' is the error line.
I DON'T KNOW WHAT I'M DOING WRONG I USED ASP.NETWebMatrix and its working
well!!
Any help!!
I have declared ItemNumber as u can see below
" :-

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
' Load array ItemNumberList with item numbers
'Dim ItemNumberList = New ArrayList
Dim ItemNumberList = New ArrayList
DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT ItemNumber FROM products1 ORDER BY ItemNumber"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
While DBReader.Read()
ItemNumberList.Add(DBReader("ItemNumber"))
End While
DBReader.Close()
DBConnection.Close()
ItemNumberList.TrimToSize()
End Sub

Dim ItemNumber As String
ItemNumber = CType(Args.Item.FindControl("ItemNumber"), TextBox).Text

Nov 18 '05 #1
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3 Replies


P: n/a
Hi,

The code in Page_Load() has nothing to do with these two lines:

Dim ItemNumber As String
ItemNumber = CType(Args.Item.FindControl("ItemNumber"), TextBox).Text

What is Args? It looks like you already know the control name. Why not?:

ItemNumber = ItemNumber.Text

That should work fine. Are the two lines of code above in another
subroutine? The code you posted doesn't seem relevant in any way to each
other. Please post a better sample of what you are trying to do. Thanks
and Good luck! Ken.

--
Ken Dopierala Jr.
For great ASP.Net web hosting try:
http://www.webhost4life.com/default.asp?refid=Spinlight
If you sign up under me and need help, email me.

"Patrick.O.Ige" <Pa*********@discussions.microsoft.com> wrote in message
news:F8**********************************@microsof t.com...
I'm loading an Array below but getting the error "Object reference not set to an instance saying 'ItemNumber = CType(Args.Item.FindControl("ItemNumber"), TextBox).Text' is the error line.
I DON'T KNOW WHAT I'M DOING WRONG I USED ASP.NETWebMatrix and its working
well!!
Any help!!
I have declared ItemNumber as u can see below
" :-

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
' Load array ItemNumberList with item numbers
'Dim ItemNumberList = New ArrayList
Dim ItemNumberList = New ArrayList
DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;") DBConnection.Open()
SQLString = "SELECT ItemNumber FROM products1 ORDER BY ItemNumber"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
While DBReader.Read()
ItemNumberList.Add(DBReader("ItemNumber"))
End While
DBReader.Close()
DBConnection.Close()
ItemNumberList.TrimToSize()
End Sub

Dim ItemNumber As String
ItemNumber = CType(Args.Item.FindControl("ItemNumber"), TextBox).Text

Nov 18 '05 #2

P: n/a
Hi Ken and thanks for the reply! (My Code below!!!)
What i'm trying to do is a datagrid that has Add,Update,Delete commands.My
Add command is working but my Delete and Update command is giving error :-
System.NullReferenceException: Object reference not set to an instance of an
object.
Refering to the line code:- ItemNumber =
CType(Args.Item.FindControl("ItemNumber"), TextBox).Text
Don't know whats wrong IT WORKS WITH ASP.NETWEBMATRIX!!
But VS.Net give such errors!
Any help Thanks!!

'Option Explicit On
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.UI.WebControls

Public Class datagrid_edit_delete
Inherits System.Web.UI.Page

'Dim ItemTypes As New ArrayList
Protected ItemTypes As New ArrayList
'Protected WithEvents ItemType As System.Web.UI.WebControls.DropDownList
Protected WithEvents Button As System.Web.UI.WebControls.Button
Protected WithEvents PageButtons As System.Web.UI.WebControls.PlaceHolder
Protected WithEvents UpdateMessage As System.Web.UI.WebControls.Label
Protected WithEvents DataGridDisplay As System.Web.UI.WebControls.DataGrid
Protected WithEvents TextBox1 As System.Web.UI.WebControls.TextBox
'Dim ItemNumberList As New ArrayList

'Protected WithEvents ItemTypes As System.Web.UI.WebControls.DropDownList


#Region " Web Form Designer Generated Code "

'This call is required by the Web Form Designer.
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()

End Sub

'NOTE: The following placeholder declaration is required by the Web Form
Designer.
'Do not delete or move it.
Private designerPlaceholderDeclaration As System.Object

Private Sub Page_Init(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Init
'CODEGEN: This method call is required by the Web Form Designer
'Do not modify it using the code editor.
InitializeComponent()
End Sub

#End Region
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
'Put user code to initialize the page here

Dim DBConnection As SqlConnection
Dim DBCommand As SqlCommand
Dim DBReader As SqlDataReader
Dim SQLString As String
Dim PageSize As Integer = 6

'-- Load array ItemNumberList with item numbers
'Dim ItemNumberList = New ArrayList
Dim ItemNumberList = New ArrayList
DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT ItemNumber FROM products1 ORDER BY ItemNumber"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
While DBReader.Read()
ItemNumberList.Add(DBReader("ItemNumber"))
End While
DBReader.Close()
DBConnection.Close()
ItemNumberList.TrimToSize()

'-- Create Paging Buttons
Dim StartIndex = 0
Dim EndIndex As Integer
Dim StartKey As String
Dim EndKey As String
Dim i As Integer

PageButtons.Controls.Clear()
For i = 1 To Math.Ceiling(ItemNumberList.Count / PageSize)

EndIndex = StartIndex + PageSize - 1
If EndIndex > ItemNumberList.Count - 1 Then
EndIndex = ItemNumberList.Count - 1
End If

StartKey = ItemNumberList(StartIndex)
EndKey = ItemNumberList(EndIndex)

Dim PageButton As Button
PageButton = New Button
PageButton.Text = i
PageButton.ID = "P" & i
PageButton.CommandName = StartKey & "|" & EndKey
PageButton.Style("width") = "20px"
PageButton.Style("background-color") = "#F0F0F0"
AddHandler PageButton.Command, AddressOf GetPage
PageButtons.Controls.Add(PageButton)

StartIndex += PageSize

Next

'== CREATE ARRAYLIST FOR BINDING ITEM TYPES

ItemTypes = New ArrayList
DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT DISTINCT ItemType FROM products1 ORDER BY
ItemType"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
While DBReader.Read()
ItemTypes.Add(DBReader("ItemType"))
End While
DBReader.Close()
DBConnection.Close()

If Not Page.IsPostBack Or ViewState("Updated") = True Then

DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT TOP " & PageSize & " * FROM products1 ORDER
BY ItemNumber"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
DataGridDisplay.DataSource = DBReader
DataGridDisplay.DataBind()
DBReader.Close()
DBConnection.Close()

Dim FirstButton As Button
FirstButton = CType(PageButtons.FindControl("P1"), Button)
FirstButton.Style("background-color") = "#990000"
FirstButton.Style("color") = "#FFFFFF"

ViewState("Updated") = False

End If

End Sub

Sub GetPage(ByVal Src As Object, ByVal Args As CommandEventArgs)

Dim DBConnection As SqlConnection
Dim DBCommand As SqlCommand
Dim DBReader As SqlDataReader
Dim SQLString As String

Dim Keys() As String
Keys = Split(Args.CommandName, "|")

DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT * FROM products1 WHERE " & _
"ItemNumber >= '" & Keys(0) & "' AND " & _
"ItemNumber <= '" & Keys(1) & "' " & _
"ORDER BY ItemNumber"
DBCommand = New SqlCommand(SQLString, DBConnection)
DBReader = DBCommand.ExecuteReader()
DataGridDisplay.DataSource = DBReader
DataGridDisplay.DataBind()
DBReader.Close()
DBConnection.Close()

'-- Highlight clicked button
Dim Item As Button
Dim ThisButton As Button
For Each Item In PageButtons.Controls
ThisButton = CType(Item, Button)
ThisButton.Style("background-color") = "#F0F0F0"
ThisButton.Style("color") = "#000000"
Next
ThisButton = CType(PageButtons.FindControl(Src.id), Button)
ThisButton.Style("background-color") = "#990000"
ThisButton.Style("color") = "#FFFFFF"

End Sub
Function SetIndex(ByVal TheItem As String)
Dim i As Integer
For i = 0 To ItemTypes.Count - 1
If TheItem = ItemTypes(i) Then
Return i
End If
Next
End Function

Sub EditRecord(ByVal Src As Object, ByVal Args As
DataGridCommandEventArgs)
Dim Command As String
Dim ItemNumber As String
Dim ItemType As String
Dim ItemSupplier As String
Dim ItemName As String
Dim ItemDescription As String
Dim ItemPrice As String
Dim ItemQuantity As String
Dim DBConnection As SqlConnection
Dim DBCommand As SqlCommand
Dim DBReader As SqlDataReader
Dim SQLString As String
Command = Args.CommandSource.Text

ItemNumber = CType(Args.Item.FindControl("ItemNumber"), TextBox).Text
ItemType = CType(Args.Item.FindControl("ItemType"),
DropDownList).SelectedItem.Text
ItemSupplier = CType(Args.Item.FindControl("ItemSupplier"),
TextBox).Text
ItemName = CType(Args.Item.FindControl("ItemName"), TextBox).Text
ItemDescription = CType(Args.Item.FindControl("ItemDescription"),
TextBox).Text
ItemPrice = CType(Args.Item.FindControl("ItemPrice"), TextBox).Text
ItemQuantity = CType(Args.Item.FindControl("ItemQuantity"),
TextBox).Text

UpdateMessage.Text = " "

Dim ValidRecord As Boolean = True

If Command = "Add" Or Command = "Update" Then

'-- CHECK FOR VALID RECORD ---

'-- Check for valid ItemNumber
If Len(ItemNumber) <> 6 Then
UpdateMessage.Text &= "- Invalid Item Number length "
ValidRecord = False
ElseIf Not IsNumeric(Right(ItemNumber, 4)) Then
UpdateMessage.Text &= "- Invalid Item Number format "
ValidRecord = False
Else
ItemNumber = UCase(ItemNumber)
End If

'-- Check for missing Item Supplier
If ItemSupplier = "" Then
UpdateMessage.Text &= "- Missing Supplier "
ValidRecord = False
End If

'-- Check for missing Item Name
If ItemName = "" Then
UpdateMessage.Text &= "- Missing Name "
ValidRecord = False
End If

'-- Check for missing Item Description
If ItemDescription = "" Then
UpdateMessage.Text &= "- Missing Description "
ValidRecord = False
End If

'-- Check for valid Item Price
If Not IsNumeric(ItemPrice) Then
UpdateMessage.Text &= "- Invalid Price format "
ValidRecord = False
End If

'-- Check for valid Item Quantity
If Not IsNumeric(ItemQuantity) Then
UpdateMessage.Text &= "- Invalid Quantity format "
ValidRecord = False
End If

If ValidRecord = True And Command = "Add" Then

'--- CHECK FOR DUPLICATE RECORD ---
DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
SQLString = "SELECT Count(*) FROM products1 WHERE ItemNumber
= '" & ItemNumber & "'"
DBCommand = New SqlCommand(SQLString, DBConnection)
If DBCommand.ExecuteScalar() <> 0 Then
UpdateMessage.Text = "- Duplicate Item Number. Record
not added."
ValidRecord = False
End If
DBConnection.Close()

End If

End If

If ValidRecord = True Then

Select Case Command

Case "Add"
SQLString = "INSERT INTO products1 " & _
"(ItemNumber, ItemType, ItemSupplier, ItemName, " & _
"ItemDescription, ItemPrice, ItemQuantity) VALUES(" & _
"'" & ItemNumber & "', " & _
"'" & ItemType & "', " & _
"'" & Replace(ItemSupplier, "'", "''") & "', " & _
"'" & Replace(ItemName, "'", "''") & "', " & _
"'" & Replace(ItemDescription, "'", "''") & "', " & _
ItemPrice & ", " & _
ItemQuantity & ")"
UpdateMessage.Text = "- Record " & ItemNumber & " added"

Case "Update"
SQLString = "UPDATE products1 SET " & _
"ItemType = '" & ItemType & "', " & _
"ItemSupplier = '" & Replace(ItemSupplier, "'", "''")
& "', " & _
"ItemName = '" & Replace(ItemName, "'", "''") & "', "
& _
"ItemDescription = '" & Replace(ItemDescription, "'",
"''") & "', " & _
"ItemPrice = " & ItemPrice & ", " & _
"ItemQuantity = " & ItemQuantity & " " & _
"WHERE ItemNumber = '" & ItemNumber & "'"
UpdateMessage.Text = "- Record " & ItemNumber & " updated"

Case "Delete"
SQLString = "DELETE FROM products1 WHERE ItemNumber = '"
& ItemNumber & "'"
UpdateMessage.Text = "- Record " & ItemNumber & " deleted"

End Select

DBConnection = New
SqlConnection("server=(local);database=Northwind;i ntegrated security=true;")
DBConnection.Open()
DBCommand = New SqlCommand(SQLString, DBConnection)
DBCommand.ExecuteNonQuery()
DBConnection.Close()

If Command = "Add" Or Command = "Delete" Then

ViewState("Updated") = True
Page_Load(Me, EventArgs.Empty)
'Page_Load(ByRef sender As System.Object, ByRef e As
System.EventArgs)
End If

End If

End Sub

End Class

Nov 18 '05 #3

P: n/a
Hi,

The datagrid.... The datagrid isn't my thing. I used it a couple times,
got frustrated, and wrote my own. Hopefully someone in the group can point
you in the right direction. I looked through the help file that comes with
VS.Net, in VS.Net they reference .controls(0) to CType() the control:

Sub MyDataGrid_Update(sender As Object, e As DataGridCommandEventArgs)
' For bound columns the edited value is stored in a Textbox.
' The TextBox is the 0th element in the column's cell.
Dim qtyText As TextBox = CType(e.Item.Cells(2).Controls(0), TextBox)
Dim priceText As TextBox = CType(e.Item.Cells(3).Controls(0),
TextBox)

Dim item As String = e.Item.Cells(1).Text
Dim qty As String = qtyText.Text
Dim price As String = priceText.Text

Here is the link to the full source:
"ms-help://MS.VSCC/MS.MSDNVS/cpref/html/frlrfSystemWebUIWebControlsDataGridC
ommandEventArgsClassTopic.htm"

Open up the help and paste that in the address bar.

I would try that. I don't know why WebMatrix would work and VS.Net
wouldn't. Good luck! Ken.

--
Ken Dopierala Jr.
For great ASP.Net web hosting try:
http://www.webhost4life.com/default.asp?refid=Spinlight
If you sign up under me and need help, email me.
Nov 18 '05 #4

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