Discuss "Create ToolTip for GridView Header" in the .Net forum.

Private Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles GridView1.RowDataBound
    '//Check the row type is header
    If e.Row.RowType = DataControlRowType.Header Then
        For Each cell As TableCell In e.Row.Cells
            For Each ctrl As Control In cell.Controls
                If ctrl.GetType().ToString().Contains("DataControlLinkButton") Then
                    cell.Attributes.Add("title", CType(ctrl, LinkButton).Text)
                End If
            Next
        Next
    End If
End Sub

private void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) 
{ 
    ////Check the row type is header 
    if (e.Row.RowType == DataControlRowType.Header) { 
        foreach (TableCell cell in e.Row.Cells) { 
            foreach (Control ctrl in cell.Controls) { 
                if (ctrl.GetType().ToString().Contains("DataControlLinkButton")) { 
                    cell.Attributes.Add("title", ((LinkButton)ctrl).Text); 
                } 
            } 
        } 
    } 
}