passing checkboxlist selected items as a concatenated string - asp.net

Question

I am trying to pass the selected items from a checkboxlist in asp.net (vs 2005/.net 2.0) as a concatenated string.
Currently my .aspx is
<asp:CheckBoxList id="checkbox1" AutoPostBack="False" AppendDataBoundItems="true" CellPadding="5" CellSpacing="5" RepeatColumns="1" RepeatDirection="Vertical" RepeatLayout="Flow" TextAlign="Right" runat="server">
<asp:ListItem Value="1">Carrots</asp:ListItem>
<asp:ListItem Value="2">Lettuce</asp:ListItem>
<asp:ListItem Value="3">Olives</asp:ListItem>
<asp:ListItem Value="4">Onions</asp:ListItem>
<asp:ListItem Value="5">Tomato</asp:ListItem>
<asp:ListItem Value="6">Pickles</asp:ListItem>
</asp:CheckBoxList>
And the .aspx.vb is (inside the Protected Sub for submit)
For Each li As ListItem In checkbox1.Items
If li.Selected = True Then
checkbox1.Text = checkbox1.Text + "," + li.Text
End If
Next
Which is written to the db via
checkbox1.Text = dv(0)("Salad").ToString()
When I select and save, I am currently getting an error
Server Error in '/' Application.
'checkbox1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value
Any thoughts on how to concatenate the selected checkbox items
For example, if some selects Carrots, Lettuce, and Tomato;
checkbox1 = 1,2,5

Answer 1

I don't think you are assigning to a variable like you describe you are returning.
string list = "";
For Each li As ListItem In chkQ4.Items
If li.Selected = True Then
list = list + "," + li.Text
End If
Next
is how you should write the line above.
In C# using linq, I would write
var list = checkbox1.Items
.Cast<ListItem>()
.Where(item => item.Selected == true)
.Select(item => item.Value);
var result = string.Join(",",list);
which I believe is the following in VB
Dim list = checkbox1.Items.Cast(Of ListItem)().Where(Function(item) item.Selected = True).[Select](Function(item) item.Value)
Dim result = String.Join(",", list.ToArray())

Answer 2

This is a little example
Markup:
<asp:CheckBoxList ID="CheckBoxList1" runat="server">
<asp:ListItem Value="1">Carrots</asp:ListItem>
<asp:ListItem Value="2">Apples</asp:ListItem>
<asp:ListItem Value="3">Lettuce</asp:ListItem>
</asp:CheckBoxList>
<br />
<asp:Literal ID="Literal1" runat="server"></asp:Literal><br />
<br />
<asp:Button ID="Button1" runat="server" Text="Concatenate" /><br />
<asp:Button ID="Button2" runat="server" Text="Save" />
Codebehind:
Private Sub SaveItems(ByVal strItems As String)
Dim cn As New SqlConnection("user id=sa;password=abcd;database=BD_Test;server=SERVNAME")
Dim cmd As New SqlCommand("Insert into CheckItems values (#ItemId)", cn)
Dim cmdPar As New SqlParameter("#ItemId", SqlDbType.Char, 1)
If strItems.Split(",").Length > 0 Then
cmd.Parameters.Add(cmdPar)
Using cn
cn.Open()
Using cmd
''Split the existing selected values, store it in an array
''and iterate to get each element of it to save it in the DB
For Each strItem As String In strItems.Split(",")
cmd.Parameters("#ItemId").Value = strItem
cmd.ExecuteNonQuery()
Next
End Using
Me.Literal1.Text = "Items saved"
End Using
End If
End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Me.Literal1.Text = ""
For Each l As ListItem In Me.CheckBoxList1.Items
''Concatenate keeping the order of the items in your CheckboxList
If l.Selected Then
Me.Literal1.Text = Me.Literal1.Text & l.Value & ","
End If
Next
''Remove the final "," in case its at the end of the string
''to avoid db issues and selected items issues
If Right(Me.Literal1.Text, 1) = "," Then
Me.Literal1.Text = Left(Me.Literal1.Text, Me.Literal1.Text.Length - 1)
End If
''You can also save the items directly after concatenating
''Me.SaveItems(Me.Literal1.Text)
End Sub
Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
Me.SaveItems(Me.Literal1.Text)
End Sub
The expected result is to have the selected values of the items on the page literal:
1,3
Hope this helps.