DropDownList in Gridview when item does not exist in ddl

V

Vincent

Hi, Using asp.net 3.5 I have a Gridview named glTrucks, which contains
a template field with a dropdownlist in it called ddlTruckDrivers1.
My problem is when I go into edit mode there is a different problem
depending on what route I take:
1. If I try to edit a row that is not in the ddlTruckDrivers list I
get the following error:
“ddlTruckDrivers1 has a SelectedValue which is invalid because it does
not exist in the list of items.
Parameter name: value”
I’ve tried Intercepting it before/while it is databound by trying to
put code in the “glTrucks _RowCreated”, “glTrucks _RowUpdating”,
“ddlTruckDrivers1_DataBound”, “ddlTruckDrivers1_DataBinding”,
“ddlTruckDrivers1_PreRender” and basically telling it if the value
does not exist in the gridview to use the first value, but It still
always throws that error. I have tried to reference a lot of articles/
blogs/newsgroups with no luck, “http://weblogs.asp.net/hpreishuber/
archive/2005/10/11/427266.aspx” being the one that best pertains to my
problem, but none of the solutions either in the articles or comments
work.
Here’s how my gridview and sqldatasource are setup:

<asp:GridView ID="glTrucks" runat="server" AutoGenerateColumns="False"
CellPadding="4" DataKeyNames="id" DataSourceID="SqlDataSource2">
<Columns>
<asp:BoundField DataField="id" HeaderText="id"
InsertVisible="False"
ReadOnly="True" SortExpression="id" />
<asp:BoundField DataField="truck" HeaderText="Truck"
SortExpression="truck" />
<asp:TemplateField HeaderText="driver"
SortExpression="driver">
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<
%# Bind("driver") %>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlTruckDrivers1"
runat="server" DataSourceID="sqlDrivers1"
DataTextField="driver"
DataValueField="driver"

ondatabinding="ddlTruckDrivers1_DataBinding"
ondatabound="ddlTruckDrivers1_DataBound"
onprerender="ddlTruckDrivers1_PreRender"

onselectedindexchanged="ddlTruckDrivers1_SelectedIndexChanged" >
</asp:DropDownList>

<asp:SqlDataSource ID="sqlDrivers1"
runat="server"
ConnectionString="<%$
ConnectionStrings:MyConnectionString %>"
SelectCommand="SELECT * FROM
[FLTranDrivers] ORDER BY [driver]">
</asp:SqlDataSource>
</EditItemTemplate>
</asp:TemplateField>

</Columns>

</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource2" runat="server"
ConnectionString="<%$ ConnectionStrings:MyConnectionString
%>"
DeleteCommand="DELETE FROM [FLTranTrucks] WHERE [id] =
@original_id"
InsertCommand="INSERT INTO [FLTranTrucks] ([truck],
[driver]) VALUES (@truck, @driver)"
OldValuesParameterFormatString="original_{0}"
SelectCommand="SELECT * FROM [FLTranTrucks]"

UpdateCommand="UPDATE [FLTranTrucks] SET [truck] = @truck,
[driver] = @driver WHERE [id] = @original_id">
<DeleteParameters>
<asp:parameter Name="original_id" Type="Int32" />
</DeleteParameters>
<UpdateParameters>
<asp:parameter Name="truck" Type="String" />
<asp:parameter Name="driver" Type="String" />
<asp:parameter Name="original_id" Type="Int32" />
</UpdateParameters>
<InsertParameters>
<asp:parameter Name="truck" Type="String" />
<asp:parameter Name="driver" Type="String" />
</InsertParameters>
</asp:SqlDataSource>

Here’s my code behind:
Protected Sub glTrucks_RowCreated(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.GridViewRowEventArgs) Handles
glTrucks.RowCreated
If e.Row.RowState.ToString = "Edit" Then
If Not
IsNothing(CType(e.Row.FindControl("ddlTruckDrivers1"),
DropDownList).Items.FindByValue(DataBinder.Eval(e.Row.DataItem,
"driver").ToString())) Then
CType(e.Row.FindControl("ddlTruckDrivers1"),
DropDownList).SelectedItem.Value = DataBinder.Eval(e.Row.DataItem,
"driver").ToString()
End If
End If
End Sub
Protected Sub glTrucks_RowUpdating(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles
glTrucks.RowUpdating
e.NewValues("driver") =
CType(glTrucks.Rows(e.RowIndex).FindControl("ddlTruckDrivers1"),
DropDownList).SelectedValue
End Sub



2. So I got frustrated and figured I would unbind ddlTruckDrivers1
but i cannot seem to figure out how to get it to set the value that
already exists in the DropDownList. I’ve tried in every event and I
cannot seem to figure out the problem

Now my only solution is to anihilate the person that asked me to
create this :) Any help would be appreciated. Thanks a lot. –Vincent.
 
V

Vincent

I answered my own question. Here's what I did to solve this:

1. Deleted the "selected value="<%# bind("driver") %>" from the
dropdownlist. (i did not have this code in my above posting)
2. Placed "Imports System.Data" at the top of my code page to
accomodate for the "DataRowView"
3. Entered the following code in my dropdownlist_databound. I got
this code from teh following website:

http://www.webswapp.com/codesamples/aspnet20/dependentlists/default.aspx
(he has codebehind in C# or VB)

Protected Sub ddlTruckDrivers1_DataBound(ByVal sender As Object,
ByVal e As System.EventArgs)
Dim ddl As DropDownList = DirectCast(sender, DropDownList)
'=== add an empty item on top of the list

Dim gvRow As GridViewRow = DirectCast(ddl.NamingContainer,
GridViewRow)
'check to see if the item exists in the gridview, if it doesn't then
it will default to the first item in the dropdownlist
If Not gvRow.DataItem Is Nothing Then
Dim strDriver As String = DirectCast(gvRow.DataItem,
DataRowView)("driver").ToString
'be careful of the possibility that the value saved on
the database does not exist
'in the valid selections that are displayed on the list
ddl.ClearSelection()
Dim li As ListItem = ddl.Items.FindByValue(strDriver)
If Not li Is Nothing Then li.Selected = True

End If
End Sub

4. This small piece of data to set the value of the update parameter:

Protected Sub glTrucks_RowUpdating(ByVal sender As Object, ByVal e
As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles
glTrucks.RowUpdating
e.NewValues("driver") =
CType(glTrucks.Rows(e.RowIndex).FindControl("ddlTruckDrivers1"),
DropDownList).SelectedValue
End Sub
 

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