Object reference not set to an instance of an object.

G

Guest

Hi All,

I have a webform with a button to add record into the database. When the
button is being clicked, the program will assign initial value controls in a
detailsview control. When the first time, the button being click, the program
works as expected. However, the next click on the button, the program showed
the following error message:

System.NullReferenceException was unhandled by user code
Message="Object reference not set to an instance of an object."
Source="App_Web_xogepfrv"
StackTrace:
at Inv_Maint.GetDefaultValue(String objMainType) in
C:\Data\OITRS\Inv_Upd.aspx.vb:line 842
at Inv_Maint.btnAddInventory_Click(Object sender, EventArgs e) in
C:\Data\OITRS\Inv_Upd.aspx.vb:line 1132
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String
eventArgument)
at
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler
sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)


Below is the code for the button:

Protected Sub btnAddInventory_Click(ByVal sender As Object, ByVal e As
System.EventArgs) Handles btnAddInventory.Click

HideAll()
btnAddInventory.Visible = False
Select Case UCase(ddlMainType.SelectedItem.Value)
Case "MONITOR"
dvInventory_Monitor.Visible = True
dvInventory_Monitor.ChangeMode(DetailsViewMode.Insert)

Case "COMPUTER"
dvInventory_Computer.Visible = True
dvInventory_Computer.ChangeMode(DetailsViewMode.Insert)
GetDefaultValue("dvInventory_Computer")

.....

Below is the the code for GetDefaultValue :
Private Sub GetDefaultValue(ByVal objMainType As String)
Select Case (objMainType)
Case "dvInventory_Computer"
CType(dvInventory_Computer.FindControl("txtMainType"),
TextBox).Text = ddlMainType.SelectedValue.ToString
CType(dvInventory_Computer.FindControl("ddlSubType"),
DropDownList).SelectedValue = ddlSubType.SelectedValue.ToString
CType(dvInventory_Computer.FindControl("txtUnitPrice"),
TextBox).Text = "0.00"
CType(dvInventory_Computer.FindControl("txtQuantity"),
TextBox).Text = "1"
CType(dvInventory_Computer.FindControl("ddlRAMType"),
DropDownList).SelectedValue = "NONE"

CType(dvInventory_Computer.FindControl("ddlNICManufacturer"),
DropDownList).SelectedValue = "NONE"
CType(dvInventory_Computer.FindControl("ddlOpticalDrive"),
DropDownList).SelectedValue = "NONE"
CType(dvInventory_Computer.FindControl("txtHDDSpace"),
TextBox).Text = Nothing
CType(dvInventory_Computer.FindControl("ddlGCManufacturer"),
DropDownList).SelectedValue = "NONE"

CType(dvInventory_Computer.FindControl("ddlModemManufacturer"),
DropDownList).SelectedValue = "NONE"

....
Please advise

Regards,
SB
 
K

Kevin Spencer

Which one is "line 842"?

--
HTH,

Kevin Spencer
Microsoft MVP
Professional Numbskull

Hard work is a medication for which
there is no placebo.
 
G

Guest

Private Sub ShowError(ByVal strMainType As String, ByVal strField As
String)
Select Case UCase(strMainType)
Case "COMPUTER"
If strField = "Manufacturer" Then

CType(dvInventory_Computer.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Computer.FindControl("lblModel_ErrMsg"), Label).Visible =
True
ElseIf strField = "SubType" Then

CType(dvInventory_Computer.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Computer.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_Computer.Visible = True

Case "NIC"
If strField = "Manufacturer" Then

CType(dvInventory_NIC.FindControl("lblManufacturer_ErrMsg"), Label).Visible =
True
ElseIf strField = "Model" Then
CType(dvInventory_NIC.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then
CType(dvInventory_NIC.FindControl("lblSubType_ErrMsg"),
Label).Visible = True
Else
CType(dvInventory_NIC.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_NIC.Visible = True

Case "OPTICALDRIVE"
If strField = "Manufacturer" Then

CType(dvInventory_ExtOD.FindControl("lblManufacturer_ErrMsg"), Label).Visible
= True
ElseIf strField = "Model" Then
CType(dvInventory_ExtOD.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then

CType(dvInventory_ExtOD.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_ExtOD.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_ExtOD.Visible = True

Case "MONITOR"
If strField = "Manufacturer" Then

CType(dvInventory_Monitor.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Monitor.FindControl("lblModel_ErrMsg"), Label).Visible =
True
ElseIf strField = "SubType" Then

CType(dvInventory_Monitor.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Monitor.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_Monitor.Visible = True

Case "PRINTER/SCANNER"
If strField = "Manufacturer" Then

CType(dvInventory_PrinterScanner.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_PrinterScanner.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then

CType(dvInventory_PrinterScanner.FindControl("lblSubType_ErrMsg"),
Label).Visible = True
Else

CType(dvInventory_PrinterScanner.FindControl("lblKey_ErrMsg"), Label).Visible
= True
End If
dvInventory_PrinterScanner.Visible = True

Case "UPS"
If strField = "Manufacturer" Then

CType(dvInventory_UPS.FindControl("lblManufacturer_ErrMsg"), Label).Visible =
True
ElseIf strField = "Model" Then
CType(dvInventory_UPS.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then
CType(dvInventory_UPS.FindControl("lblSubType_ErrMsg"),
Label).Visible = True
Else
CType(dvInventory_UPS.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_UPS.Visible = True

Case "SOFTWARE"
If strField = "Manufacturer" Then

CType(dvInventory_Software.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Software.FindControl("lblModel_ErrMsg"), Label).Visible =
True
ElseIf strField = "SubType" Then

CType(dvInventory_Software.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Software.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_Software.Visible = True

Case "NETWORKING"
If strField = "Manufacturer" Then

CType(dvInventory_Networking.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Networking.FindControl("lblModel_ErrMsg"), Label).Visible =
True
ElseIf strField = "SubType" Then

CType(dvInventory_Networking.FindControl("lblSubType_ErrMsg"), Label).Visible
= True
Else

CType(dvInventory_Networking.FindControl("lblKey_ErrMsg"), Label).Visible =
True
End If
dvInventory_Networking.Visible = True

Case "MODEM"
If strField = "Manufacturer" Then

CType(dvInventory_Modem.FindControl("lblManufacturer_ErrMsg"), Label).Visible
= True
ElseIf strField = "Model" Then
CType(dvInventory_Modem.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then

CType(dvInventory_Modem.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Modem.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_Modem.Visible = True

Case "ACCESSORIES"
If strField = "Manufacturer" Then

CType(dvInventory_Accessories.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Accessories.FindControl("lblModel_ErrMsg"), Label).Visible
= True
ElseIf strField = "SubType" Then

CType(dvInventory_Accessories.FindControl("lblSubType_ErrMsg"),
Label).Visible = True
Else

CType(dvInventory_Accessories.FindControl("lblKey_ErrMsg"), Label).Visible =
True
End If
dvInventory_Accessories.Visible = True

Case "STORAGE"
If strField = "Manufacturer" Then

CType(dvInventory_Storage.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then

CType(dvInventory_Storage.FindControl("lblModel_ErrMsg"), Label).Visible =
True
ElseIf strField = "SubType" Then

CType(dvInventory_Storage.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Storage.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
dvInventory_Storage.Visible = True

Case "OTHERS"
If strField = "Manufacturer" Then

CType(dvInventory_Others.FindControl("lblManufacturer_ErrMsg"),
Label).Visible = True
ElseIf strField = "Model" Then
CType(dvInventory_Others.FindControl("lblModel_ErrMsg"),
Label).Visible = True
ElseIf strField = "SubType" Then

CType(dvInventory_Others.FindControl("lblSubType_ErrMsg"), Label).Visible =
True
Else
CType(dvInventory_Others.FindControl("lblKey_ErrMsg"),
Label).Visible = True
End If
Line 842: dvInventory_Others.Visible = True

End Select
End Sub
 
K

Kevin Spencer

Interesting. So, you're telling me that *all* of this is "line 842"?

--
HTH,

Kevin Spencer
Microsoft MVP
Professional Numbskull

Hard work is a medication for which
there is no placebo.
 
?

=?ISO-8859-1?Q?G=F6ran_Andersson?=

No, he actually marked the line with "Line 842:". I just saw it by
chance. It's the third line from the end in the large chunk of code.
 
K

Kevin Spencer

Okay. That line reads:

dvInventory_Others.Visible = True

Apparently, dvInventory_Others is null (Nothing).

--
HTH,

Kevin Spencer
Microsoft MVP
Professional Numbskull

Hard work is a medication for which
there is no placebo.
 

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