Hi Faiz,
You won't be able to get this directly from any of the .net class and it will be difficult if you are using any 3rd party gridview or ajax. But you will able to do so if you try with the basic.
in keypress event catch the key and then increment the selected row by 1.
TextBox1.Attributes.Add("OnKeyPress", "GetKeyPress()")
In the Default.ASPX Code page, I have
<script>
Function GetKeyPress()
{
alert("you Pressed " & event.KeyCode;
}
</script>
now within this function you can use something like this
GridView gv = new GridView();
GridViewRow r = gv.SelectedRow;
gv.SelectedRow.RowIndex = r.RowIndex + 1;
this might now work as of now because i havent done this on VS .. please try and let me know in case of any issue.
All the best!!