Please Please Please help

I am trying to populate a second dropdownlist from the first.  both dropdownlists are displayed inside the datagrid.  I can populate the first one easily but my onselectedindexchanged event states:

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:

Line 195:
Line 196:
Line 197: if lstCPUMan.Selectedvalue = "Dell" then
Line 198: lstCPUMod.items.Add("Optiplex GX110")
Line 199: lstCPUMod.items.Add("Optiplex GX260")

Source File: C:\Inetpub\wwwroot\LocSearch.aspx Line: 197
Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
ASP.LocSearch_aspx.lstCPUMan_selectedindexchanged(Object sender, EventArgs e) in C:\Inetpub\wwwroot\LocSearch.aspx:197
System.Web.UI.WebControls.ListControl.OnSelectedIndexChanged(EventArgs e) +108
System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent() +26
System.Web.UI.Page.RaiseChangedEvents() +115
System.Web.UI.Page.ProcessRequestMain() +1081

Version Information: Microsoft .NET Framework Version:1.1.4322.573; ASP.NET Version:1.1.4322.573
here is the code:

Function CPUSearch(ByVal Location As String, byval strsortfield as string) As System.Data.DataSet
Dim connectionString As String = "server='snake'; user id='sa'; password='<Secret>'; Database='PayPal_Inventory'"& _
Dim sqlConnection As System.Data.SqlClient.SqlConnection = New System.Data.SqlClient.SqlConnection(connectionString)
Dim queryString As String = "SELECT [CPU].* FROM [CPU] WHERE ([CPU].[Location] = @Location) Order by " & strsortfield
Dim sqlCommand As System.Data.SqlClient.SqlCommand = New System.Data.SqlClient.SqlCommand(queryString, sqlConnection)
sqlCommand.Parameters.Add("@Location", System.Data.SqlDbType.VarChar).Value = location
Dim dataAdapter As System.Data.SqlClient.SqlDataAdapter = New System.Data.SqlClient.SqlDataAdapter(sqlCommand)
Dim dataSet As System.Data.DataSet = New System.Data.DataSet
dgrdCPU.datasource = dataset
Return dataSet
End Function

Function CPUUpdate(ByVal ID As String, ByVal cPUPPID As String, ByVal cPUMan As String, ByVal cPUMod As String, ByVal cPUSN As String) As Integer
Dim connectionString As String = "server='snake'; user id='sa'; password='v!k!ng57373'; Database='PayPal_Inventory'"& _
Dim sqlConnection As System.Data.SqlClient.SqlConnection = New System.Data.SqlClient.SqlConnection(connectionString)
Dim queryString As String = "UPDATE [CPU] SET [PayPal_ID]=@CPUPPID, [Manufacturer]=@CPUMan, [Model]=@CPUMod, ["& _
"SN#]=@CPUSN WHERE ([CPU].[ID] = @ID)"
Dim sqlCommand As System.Data.SqlClient.SqlCommand = New System.Data.SqlClient.SqlCommand(queryString, sqlConnection)
sqlCommand.Parameters.Add("@ID", System.Data.SqlDbType.VarChar).Value = ID
sqlCommand.Parameters.Add("@CPUPPID", System.Data.SqlDbType.VarChar).Value = cPUPPID
sqlCommand.Parameters.Add("@CPUMan", System.Data.SqlDbType.VarChar).Value = cPUMan
sqlCommand.Parameters.Add("@CPUMod", System.Data.SqlDbType.VarChar).Value = cPUMod
sqlCommand.Parameters.Add("@CPUSN", System.Data.SqlDbType.VarChar).Value = cPUSN
Dim rowsAffected As Integer = 0
rowsAffected = sqlCommand.ExecuteNonQuery
End Try
Return rowsAffected
End Function
sub dgrdCPU_sort(server as object, e as datagridsortcommandeventargs)
CPUSearch(txtlocation.text, e.sortexpression)
end sub
sub dgrdCPU_Edit(server as object, e as datagridcommandeventargs)
dgrdCPU.edititemindex = ctype(e.item.itemindex, Integer)
dgrdCPU.datasource = CPUsearch(txtLocation.text, "PayPal_ID")
end sub
sub dgrdCPU_Cancel(Server as object, e as datagridcommandeventargs)
dgrdCPU.edititemindex = -1
dgrdCPU.datasource = CPUsearch(txtLocation.text, "PayPal_ID")
end sub
sub dgrdCPU_Update(server as object, e as datagridcommandeventargs)

dim ID as integer = e.item.cells(0).text
dim CPUPPID_Value as textbox = e.item.cells(2).controls(0)
dim CPUMan_Value as string = ctype(e.item.findcontrol("lstCPUMan"), dropdownlist).selecteditem.value

dim CPUMod_Value as string = ctype(e.item.findcontrol("lstCPUMod"), dropdownlist).selecteditem.value
dim CPUSN_Value as textbox = e.item.cells(5).controls(0)
CPUUpdate(ID, CPUPPID_Value.text, CPUMan_Value, CPUMod_Value, CPUSN_Value.text)
dgrdCPU.editItemIndex = -1
dgrdCPU.datasource = CPUSearch(txtLocation.text, "PayPal_ID")
end sub
sub dgrdCPU_itemdatabound(sender as object, e as datagriditemeventargs)
dim itemtype as listitemtype = e.item.itemtype
if(itemtype = listitemtype.edititem) then
dim lstCPUMan as dropdownlist= ctype(e.item.findcontrol("lstCPUMan"), dropdownlist)
dim myrow as datarowview = ctype(e.item.dataitem, datarowview)
dim myrole as string = myrow("Manufacturer").tostring()
lstCPUMan.datatextfield = "Manufacturer"
lstCPUMan.datavaluefield = "Manufacturer"
dgrdCPU.datasource = CPUSearch(txtlocation.text, "PayPal_ID")
lstCPUMan.items.findbytext(myrole).selected = true
end if
end sub
sub lstCPUMan_selectedindexchanged(sender As Object, e As EventArgs)

if lstCPUMan.Selectedvalue = "Dell" then
lstCPUMod.items.Add("Optiplex GX110")
lstCPUMod.items.Add("Optiplex GX260")
lstCPUMod.items.Add("Optiplex GX270")
else if lstCPUMan.Selectedvalue = "Hewlet Packard" then
lstCPUMod.items.Add("Vectra VL400 MT")
lstCPUMod.items.Add("Vectra VL420 MT")
lstCPUMod.items.Add("Brio SA 410")
lstCPUMod.items.add("Xeon X4000")
else if lstCPUMan.Selectedvalue = "IBM" then
lstCPUMod.items.Add("Netvista 8307-25U")
end if
end sub
here is the html:
<asp:DataGrid id="dgrdCPU" runat="server" Width="511px" onupdatecommand="dgrdCPU_Update" AllowSorting="True" BorderStyle="Solid" BorderColor="Navy" BorderWidth="2px" onsortcommand="dgrdCPU_sort" AutoGenerateColumns="False" oneditcommand="dgrdCPU_edit" oncancelcommand="dgrdCPU_cancel" onload="page_Load" autopostback="true">
<HeaderStyle font-underline="True" font-bold="True" forecolor="#000040" borderstyle="Solid" bordercolor="Navy" backcolor="Teal"></HeaderStyle>
<AlternatingItemStyle borderwidth="3px" borderstyle="Solid" bordercolor="Navy" backcolor="#00C0C0"></AlternatingItemStyle>
<asp:BoundColumn DataField="ID" ReadOnly="True" HeaderText="ID"></asp:BoundColumn>
<asp:BoundColumn DataField="Location" ReadOnly="True" HeaderText="Location"></asp:BoundColumn>
<asp:BoundColumn DataField="PayPal_ID" SortExpression="PayPal ID" HeaderText="PayPal ID"></asp:BoundColumn>
<asp:TemplateColumn SortExpression="Manufacturer" HeaderText="Manufacturer">
<asp:Label runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Manufacturer") %>'></asp:Label>
<asp:dropdownlist id="lstCPUMan" onselectedindexchanged="lstCPUMan_selectedIndexChanged" autopostback= "true" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Manufacturer") %>'>

<asp:ListItem Value="Dell">Dell</asp:ListItem>
<asp:ListItem Value="Hewlet Packard">Hewlet Packard</asp:ListItem>
<asp:ListItem Value="IBM">IBM</asp:ListItem>
<asp:TemplateColumn SortExpression="model" HeaderText="Model">
<asp:Label runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Model") %>'></asp:Label>
<asp:dropdownlist id="lstCPUMod" runat="server" ></asp:Dropdownlist>
<asp:BoundColumn DataField="SN#" SortExpression="Serial #" HeaderText="Serial #"></asp:BoundColumn>
<asp:EditCommandColumn ButtonType="LinkButton" UpdateText="Update" CancelText="Cancel" EditText="Edit"></asp:EditCommandColumn>

12/3/2003 8:59:16 AM 93655 articles. 6 followers. Follow

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First of all I have to ask you to use the < code></ code> tags to improve readbility of your code in the future. I have done this for you this time. I also suggest you do NOT leave your SQL Server password, which I also removed.

In your lstCPUMan_selectedindexchanged method, try using Findcontrol:

Dim myMAN As DropdownList = Ctype(Page.FindControl("lstCPUMan"),DropDownList)
Dim myMOD As DropdownList = Ctype(Page.FindControl("lstCPUMod"),DropDownList)
If myMAN.Selectedvalue = "Dell" then
myMOD.items.Add("Optiplex GX110")
myMOD.items.Add("Optiplex GX260")


Andre Colbiornsen
Seventh Day
Råbygatan 1A,
SE-223 61 Lund
Mob.: +46-(0)708-97 78 79
12/3/2003 9:05:00 AM
No dice,  after selecting MyMan the debugger shows the value as nothing.
12/3/2003 10:46:59 PM
I found the code to do it, thanks to 4guysfromrolla  here is the code

Dim CPUMAN As dropdownlist = sender
dim dgrdCPU as datagriditem = CPUMan.parent.parent
Dim CPUMoD As dropdownlist = dgrdCPU.findcontrol("lstCPUMod")
dim CPUManID as string = CPUMan.selecteditem.value
if CPUManID = "Dell" then
CPUMod.items.Add("Optiplex GX110")
CPUMod.items.Add("Optiplex GX260")
CPUMod.items.Add("Optiplex GX270")
CPUMod.items.add("Precision 650")
else if CPUManID = "Hewlet Packard" then
CPUMod.items.Add("Vectra VL400 MT")
CPUMod.items.Add("Vectra VL420 MT")
CPUMod.items.Add("Brio SA 410")
CPUMod.items.add("Xeon X4000")
else if CPUManID = "IBM" then
CPUmod.items.Add("Netvista 8307-25U")
end if

12/5/2003 5:07:15 AM

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