Whats the error:- System.NullRefe renceException:

[Patrick.O.Ige]

What could cause the error:-
System.NullRefe renceException: Object reference not set to an instance of an
object.
Any ideas?

[Chris Austin]

Your code is attempting reference an object that is currently equal to Null
(or, Nothing if you are using VB).

-Chris
~
http://weblogs.austinspad.com/caustin

"Patrick.O. Ige" <Pa*********@di scussions.micro soft.com> wrote in message
news:EE******** *************** ***********@mic rosoft.com...

What could cause the error:-
System.NullRefe renceException: Object reference not set to an instance of
an
object.
Any ideas?

[Karl Seguin]

If you showed us some code, we'd probably be more likely to point out the
exact error..especial ly if you could provide a line #

Karl

--
MY ASP.Net tutorials
http://www.openmymind.net/
"Patrick.O. Ige" <Pa*********@di scussions.micro soft.com> wrote in message
news:EE******** *************** ***********@mic rosoft.com...

What could cause the error:-
System.NullRefe renceException: Object reference not set to an instance of an object.
Any ideas?

[Patrick.O.Ige]

Well what i have is a Datagrid that ,Updates,Adds and Delete.
When i add i have no error but when i click Update and Delete commands it
fires an error..
The Error line is at :-

"ItemNumber = CType(Args.Item .FindControl("I temNumber"), TextBox).Text"

Any ideas?

My code is below(its my EditRecord Sub porgram):-
Sub EditRecord(ByVa l Src As Object, ByVal Args As DataGridCommand EventArgs)
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.CommandSou rce.Text

ItemNumber = CType(Args.Item .FindControl("I temNumber"), TextBox).Text
ItemType = CType(Args.Item .FindControl("I temType"),
DropDownList).S electedItem.Tex t
ItemSupplier = CType(Args.Item .FindControl("I temSupplier"),
TextBox).Text
ItemName = CType(Args.Item .FindControl("I temName"), TextBox).Text
ItemDescription = CType(Args.Item .FindControl("I temDescription" ),
TextBox).Text
ItemPrice = CType(Args.Item .FindControl("I temPrice"), TextBox).Text
ItemQuantity = CType(Args.Item .FindControl("I temQuantity"),
TextBox).Text

UpdateMessage.T ext = " "

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.T ext &= "- Invalid Item Number length "
ValidRecord = False
ElseIf Not IsNumeric(Right (ItemNumber, 4)) Then
UpdateMessage.T ext &= "- Invalid Item Number format "
ValidRecord = False
Else
ItemNumber = UCase(ItemNumbe r)
End If

'-- Check for missing Item Supplier
If ItemSupplier = "" Then
UpdateMessage.T ext &= "- Missing Supplier "
ValidRecord = False
End If

'-- Check for missing Item Name
If ItemName = "" Then
UpdateMessage.T ext &= "- Missing Name "
ValidRecord = False
End If

'-- Check for missing Item Description
If ItemDescription = "" Then
UpdateMessage.T ext &= "- Missing Description "
ValidRecord = False
End If

'-- Check for valid Item Price
If Not IsNumeric(ItemP rice) Then
UpdateMessage.T ext &= "- Invalid Price format "
ValidRecord = False
End If

'-- Check for valid Item Quantity
If Not IsNumeric(ItemQ uantity) Then
UpdateMessage.T ext &= "- Invalid Quantity format "
ValidRecord = False
End If

If ValidRecord = True And Command = "Add" Then

'--- CHECK FOR DUPLICATE RECORD ---
DBConnection = New
SqlConnection(" server=(local); database=Northw ind;integrated security=true;" )
DBConnection.Op en()
SQLString = "SELECT Count(*) FROM products1 WHERE ItemNumber
= '" & ItemNumber & "'"
DBCommand = New SqlCommand(SQLS tring, DBConnection)
If DBCommand.Execu teScalar() <> 0 Then
UpdateMessage.T ext = "- Duplicate Item Number. Record
not added."
ValidRecord = False
End If
DBConnection.Cl ose()

End If

End If

If ValidRecord = True Then

Select Case Command

Case "Add"
SQLString = "INSERT INTO products1 " & _
"(ItemNumbe r, ItemType, ItemSupplier, ItemName, " & _
"ItemDescriptio n, ItemPrice, ItemQuantity) VALUES(" & _
"'" & ItemNumber & "', " & _
"'" & ItemType & "', " & _
"'" & Replace(ItemSup plier, "'", "''") & "', " & _
"'" & Replace(ItemNam e, "'", "''") & "', " & _
"'" & Replace(ItemDes cription, "'", "''") & "', " & _
ItemPrice & ", " & _
ItemQuantity & ")"
UpdateMessage.T ext = "- Record " & ItemNumber & " added"

Case "Update"
SQLString = "UPDATE products1 SET " & _
"ItemType = '" & ItemType & "', " & _
"ItemSuppli er = '" & Replace(ItemSup plier, "'", "''")
& "', " & _
"ItemName = '" & Replace(ItemNam e, "'", "''") & "', "
& _
"ItemDescriptio n = '" & Replace(ItemDes cription, "'",
"''") & "', " & _
"ItemPrice = " & ItemPrice & ", " & _
"ItemQuanti ty = " & ItemQuantity & " " & _
"WHERE ItemNumber = '" & ItemNumber & "'"
UpdateMessage.T ext = "- Record " & ItemNumber & " updated"

Case "Delete"
SQLString = "DELETE FROM products1 WHERE ItemNumber = '"
& ItemNumber & "'"
UpdateMessage.T ext = "- Record " & ItemNumber & " deleted"

End Select

DBConnection = New
SqlConnection(" server=(local); database=Northw ind;integrated security=true;" )
DBConnection.Op en()
DBCommand = New SqlCommand(SQLS tring, DBConnection)
DBCommand.Execu teNonQuery()
DBConnection.Cl ose()

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

ViewState("Upda ted") = True
Page_Load(Me, EventArgs.Empty )
'Page_Load(ByRe f sender As System.Object, ByRef e As
System.EventArg s)
End If

End If

End Sub
"Karl Seguin" wrote:

If you showed us some code, we'd probably be more likely to point out the
exact error..especial ly if you could provide a line #

Karl

--
MY ASP.Net tutorials
http://www.openmymind.net/
"Patrick.O. Ige" <Pa*********@di scussions.micro soft.com> wrote in message
news:EE******** *************** ***********@mic rosoft.com...

What could cause the error:-
System.NullRefe renceException: Object reference not set to an instance of

an

object.
Any ideas?

[Jarmo Muukka]

Hello,

You het the error because Args.Item.FindC ontrol("ItemNum ber") does not find
the control and returns Nothing and/or the found control is not TextBox. You
cast the control to TextBox and if it is not a TextBox, it returns Nothing.
I assume that VB .NET works similarry than "control as TextBox" which
returns null, if the control is null or is not a TextBox. Then you try to
use its property.

It's basically the same if you do this:

Control control = null;
TextBox textBox = control as TextBox;
string text = textBox.Text; // exception happens in here

or this:

Label label = new Label();
TextBox textBox = label as TextBox;
string text = textBox.Text; // exception happens in here

JMu

"Patrick.O. Ige" <Pa*********@di scussions.micro soft.com> wrote in message
news:FA******** *************** ***********@mic rosoft.com...

Well what i have is a Datagrid that ,Updates,Adds and Delete.
When i add i have no error but when i click Update and Delete commands it
fires an error..
The Error line is at :-

"ItemNumber = CType(Args.Item .FindControl("I temNumber"), TextBox).Text"

Any ideas?

[Patrick.O.Ige]

Thx Jarmo the reply.
But my html looks like the following below and ItemNumber is TEXTBOX!
I don't know why its returning Null then!
Its works with ASP.NET WebMatrix but gives the error with VStudio .Net!!!

<asp:DataGrid id="DataGridDis play" Width="560px" runat="server"
OnItemCommand=" EditRecord"
AutoGenerateCol umns="False"
BackColor="#F9F 9F9"
HeaderStyle-BackColor="#990 000"
HeaderStyle-ForeColor="#FFF FFF"
HeaderStyle-Font-Bold="True"
HeaderStyle-HorizontalAlign ="Center"
HeaderStyle-VerticalAlign=" Top"
ItemStyle-VerticalAlign=" Top"
ItemStyle-HorizontalAlign ="Center">

<Columns>

<asp:TemplateCo lumn>
<HeaderTemplate >
No<br>
<asp:TextBox id="ItemNumber " runat="server"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemNumber " runat="server"
Text='<%# Container.DataI tem("ItemNumber ") %>'
ReadOnly="True"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Type<br>
<asp:DropDownLi st id="ItemType" runat="server"
DataSource='<%# ItemTypes %>'/>
</HeaderTemplate>
<ItemTemplate >
<asp:DropDownLi st id="ItemType" runat="server"
DataSource='<%# ItemTypes %>'
SelectedIndex=' <%# SetIndex(Contai ner.DataItem("I temType")) %>'/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Supplier<br>
<asp:TextBox id="ItemSupplie r" runat="server"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemSupplie r" runat="server"
Text='<%# Container.DataI tem("ItemSuppli er") %>'/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Name<br>
<asp:TextBox id="ItemName" runat="server"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemName" runat="server"
Text='<%# Container.DataI tem("ItemName") %>'/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Description<br>
<asp:TextBox id="ItemDescrip tion" runat="server"
TextMode="Multi Line"
Cols="25"
Rows="2"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemDescrip tion" runat="server"
Text='<%# Container.DataI tem("ItemDescri ption") %>'
TextMode="Multi Line"
Cols="25"
Rows="2"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Price<br>
<asp:TextBox id="ItemPrice" runat="server"
Text="0.00"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemPrice" runat="server"
Text='<%# FormatNumber(Co ntainer.DataIte m("ItemPrice"), 2) %>'/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
Qty<br>
<asp:TextBox id="ItemQuantit y" runat="server"
Text="0"/>
</HeaderTemplate>
<ItemTemplate >
<asp:TextBox id="ItemQuantit y" runat="server"
Text='<%# Container.DataI tem("ItemQuanti ty") %>'/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
<br>
<asp:Button Text="Add" runat="server"/>
</HeaderTemplate>
<ItemTemplate >
<asp:Button Text="Update" runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn>
<HeaderTemplate >
<br>
</HeaderTemplate>
<ItemTemplate >
<asp:Button Text="Delete" runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

</Columns>

</asp:DataGrid>
"Jarmo Muukka" wrote:

Hello,

You het the error because Args.Item.FindC ontrol("ItemNum ber") does not find
the control and returns Nothing and/or the found control is not TextBox. You
cast the control to TextBox and if it is not a TextBox, it returns Nothing.
I assume that VB .NET works similarry than "control as TextBox" which
returns null, if the control is null or is not a TextBox. Then you try to
use its property.

It's basically the same if you do this:

Control control = null;
TextBox textBox = control as TextBox;
string text = textBox.Text; // exception happens in here

or this:

Label label = new Label();
TextBox textBox = label as TextBox;
string text = textBox.Text; // exception happens in here

JMu

"Patrick.O. Ige" <Pa*********@di scussions.micro soft.com> wrote in message
news:FA******** *************** ***********@mic rosoft.com...

Well what i have is a Datagrid that ,Updates,Adds and Delete.
When i add i have no error but when i click Update and Delete commands it
fires an error..
The Error line is at :-

"ItemNumber = CType(Args.Item .FindControl("I temNumber"), TextBox).Text"

Any ideas?