Maintain Tab index after post back with textchanged - asp.net

Question

I have 3 textboxes that have AutoPostBack = true. On postback it's losing it's focus. I've been searching and tried many things but nothing is working.
The code below is a snippet of what i'm trying to do.
basically this first snippet isn't grabbing anything. Does anyone know what i'm doing wrong here
**Side note I'm not using Update Panel i'm using LayoutItemNestedControlContainer
Dim ctrl = From control In wcICausedPostBack.Parent.Controls.OfType(Of WebControl)()
Where control.TabIndex > indx
Select control
Protected Sub txtDEPTH_TextChanged(sender As Object, e As EventArgs) Handles txtDEPTH.TextChanged
UpdateProductTemp()
txtDEPTH.Focus()
End Sub
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
If Page.IsPostBack Then
Dim wcICausedPostBack As WebControl = CType(GetControlThatCausedPostBack(TryCast(sender, Page)), WebControl)
Dim indx As Integer = wcICausedPostBack.TabIndex
Dim ctrl = From control In wcICausedPostBack.Parent.Controls.OfType(Of WebControl)()
Where control.TabIndex > indx
Select control
ctrl.DefaultIfEmpty(wcICausedPostBack).First().Focus()
End If
End Sub
Protected Function GetControlThatCausedPostBack(ByVal page As Page) As Control
Dim control As WebControl = Nothing
Dim ctrlname As String = page.Request.Params.[Get]("__EVENTTARGET")
If ctrlname IsNot Nothing AndAlso ctrlname <> String.Empty Then
control = page.FindControl(ctrlname)
Else
For Each ctl As String In page.Request.Form
Dim c As Control = page.FindControl(ctl)
If TypeOf c Is TextBox OrElse TypeOf c Is DropDownList Then
control = c
Exit For
End If
Next
End If
Return control
End Function

Answer 1

Which version are you using? Because, when I try to set focus() of a Textbox, the compiler gives me an error, because there is no such method. However, HTML provides an attribute, which auto focuses an focusable element.
Solution:
TextBoxToSetFocus.Attributes.Add("autofocus", "")
Regards,
Maheshvara