Where is my dynamic control after I submit the form? - asp.net

Question

I created a dynamic form with a repeater.
<asp:repeater ID="fieldRepeater" OnItemDataBound="dataBound" runat="server">
<itemtemplate>
<div id="controlRow" class="row" runat="server">
<div id="testContainer" class="col-md-2" runat="server">
</div>
</div>
</itemtemplate>
</asp:repeater>
in codebehind I created the field I want to appear in it.
Protected Sub dataBound(ByVal sender As Object, e As RepeaterItemEventArgs)
dim temp as new DropDownList
dim tempLabel as new label
Dim testContainer As HtmlGenericControl = e.Item.FindControl("testContainer")
'createField
temp.ID = "testField" & e.Item.ItemIndex 'this is testField0
temp.Items.Add(New ListItem("Not Used", 0))
temp.Items.Add(New ListItem("Used", 1))
temp.CssClass = "form-control"
'createLabel
tempLabel.ID = "testFieldLabel" & e.Item.ItemIndex
tempLabel.AssociatedControlID = "testField" & e.Item.ItemIndex
tempLabel.Text = dr("controlLabel")
testContainer.Controls.Add(temp)
testContainer.Controls.Add(tempLabel)
end sub
The form works beautifully and I can even pre-populate it with data from a db, but in my submit handler my controls don't exist:
Protected Sub submit_Click(ByVal sender As Object, ByVal e As EventArgs) Handles submit.Click
Dim i As Int32 = 0
For Each r As DataRow ...
'db stuff
Dim temp As New DropDownList
temp = Me.FindControl("testField" & i.ToString)
'db stuff
i += 1
next
end sub
temp = Me.FindControl("testField" & i.ToString) is always nothing Can someone help me find out why?
My HTML output looks like:
<div id="cntMain_fieldRepeater_testContainer_0" class="col-md-2">
<label for="cntMain_fieldRepeater_testField0_0" id="cntMain_fieldRepeater_testFieldLabel0_0" style="color:#007AFF;">Activity</label>
<select name="ctl00$cntMain$fieldRepeater$ctl00$testField0" id="cntMain_fieldRepeater_testField0_0" class="form-control">
<option value="0">Not Used</option>
<option value="1">Used</option>
</select>
</div>

Answer 1

Dynamically created Controls need to be (re)created on every Page Load, and that includes a PostBack. So you have to move the DataBinding of the Repeater outside the !IsPostBack check.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
fieldRepeater.DataSource = loadDataHere
fieldRepeater.DataBind
End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
Dim i As Integer = 0
For Each item As RepeaterItem In fieldRepeater.Items
Dim temp As DropDownList = CType(item.FindControl(("testField" + i.ToString)),DropDownList)
temp.BackColor = Color.Red
i = (i + 1)
Next
End Sub