Register library in asp.net

 Register library in asp.net or import library in asp.net or using library in asp.net:-

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

<%@ Import Namespace="System" %>

<%@ Import Namespace="System.Data" %>

  <%

        Dim dt As New DataTable

        If (IsNothing(Session("bill_data")) = False) Then

            dt = Session("bill_data")

        End If

        Dim pg = Request.QueryString("pg")

    %>