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Drop down list items appended on postback (need replaced)

I have 2 drop down boxes. When a selection is made from the first one then the second is populated based on the selection. If the selection is changed in the first drop down then the second list has the items for the new selection but also retains the items from previous selections.
I want all the items in DDL2 to be wiped and replaced with the new items not appended.
Did that make sense?
I have tried using
Protected Sub DDGroups_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DDGroups.SelectedIndexChanged
        DDCats.ClearSelection()
        DDCats.DataBind()
    End Sub

But no good
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QPR
Asked:
QPR
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2 Solutions
 
GuitarRichCommented:
try using DDCats.Items.Clear() - although I would have thought the databind would already clear the items.
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M3mph15Commented:
Hi,

Firstly make sure that AppendDataBoundItems is set to false for the dropdownlist.

Also if the automatic methods do work, you can do manually:

For i = 0 To DDCats.Items.Count - 1
            DDCats.Items.RemoveAt(0)
Next

This will remove all items.

HTH
-M3mph15
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QPRAuthor Commented:
"AppendDataBoundItems is set to false "

this is set to true as I need to add a default value.
<asp:ListItem Value="0" Text="Category"></asp:ListItem>
I use this because I don't want them to not select a category which would have the affect of selecting the top one by default. My required field validator has an initial value of 0
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QPRAuthor Commented:
DDCats.Items.Clear()
works perfectly - now if I could get it to re-append my default item...
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M3mph15Commented:
Before you clear DDCats save the default item.

I'm going to assume its your first item. So something like ListItem liDefault = DDCats.Items(0);
Then you can add the item back to DDCats after you clear it

-M3mph15
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QPRAuthor Commented:
How do i save the default item?
What I need is a code behind version of this:
<asp:ListItem Value="0" Text="Category"></asp:ListItem>

I have tried
DDCats.Items.Clear()
        DDCats.Items.Add("Category")
        DDCats.DataBind()

which puts "category" at the top but it has no value and so slips past the validation
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M3mph15Commented:
Ok 2 ways.

1 is by saving the value that is already there:

ListItem li = new ListItem()
li = DDCats.Items(<index>)  //index is the index of the default item...first item is index 0.
DDCats.Clear()
DDCats.Items.Add(li)
DDCats.DataBind()

2 is if the value of the default value is always the same then you can hardcode it...but i wouldn't recommend incase you want to change it:

ListItem li = new ListItem()
li.Text = "<text that is shown in the dropdownlist>"
li.Value = "<value>"
DDCats.Clear()
DDCats.Items.Add(li)
DDCats.DataBind()

HTH
-M3mph15

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QPRAuthor Commented:
looks good thanks I'll try it when at work tomorrow.
"Select a category" has the value 0
This will always be zero as the categories from the DB have a CatID and that CatID is an identity field which can never be zero. By using a required field validator and saying the initial value = 0 I can always be sure that a user has not overlooked the drop down list and is required to select a proper category from it before submitting.
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QPRAuthor Commented:
Had to alter the first line as am using vb.net but this (below) works perfectly thanks!
        Dim li = New ListItem()
        li.Text = "Category"
        li.Value = "0"
        DDCats.Items.Clear()
        DDCats.Items.Add(li)
        DDCats.DataBind()


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