In the aspx page there are two controls one is text box and one more is button
Main concept here is set the focus on the textbox onclick of the button as below in the aspx.vb
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'Assigning the textbox text
Me.TextBox1.Text = "aaaaaaaaaaaaa ssssssssssssss dddddddddddd ffffffffffffffff gggggggggggggggg hhhhhhhhh"
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
'SEtting the focus on the textbox