Pass multiple values for single QueryString Parameter in ASP.Net

okey now i have solved 

on button click

 protected void Button1_Click(object sender, EventArgs e)
    {
        
        ArrayList brandarray = new ArrayList();
        brandarray.Add("brand");
        brandarray.Add("brand2");
        brandarray.Add("brand3");
        brandarray.Add("brand4");


        string arry = String.Join(",", ((string[])brandarray.ToArray(typeof(String))));


        ArrayList pricearr1 = new ArrayList();
        pricearr1.Add("price");
            pricearr1.Add("price2");
            pricearr1.Add("price3");
            pricearr1.Add("price4");


            string arry1 = String.Join(",", ((string[])pricearr1.ToArray(typeof(String))));

            ArrayList Attributearray = new ArrayList();
            Attributearray.Add("Attribute");
            Attributearray.Add("Attribute2");
            Attributearray.Add("Attribute3");
            Attributearray.Add("Attribute4");


            string arry12 = String.Join(",", ((string[])Attributearray.ToArray(typeof(String))));


            Response.Redirect("Default.aspx?brand=" + arry + " &price=" + arry1 + " &Discount=" + arry12);
    }

query string 

http://localhost:49252/Default.aspx?brand=brand,brand2,brand3,brand4%20&price=price,price2,price3,price4%20&Discount=Discount,Discount2,Discount3,Discount4