sql.cs

public static SqlConnection Connection
{
    get
    {
        var ctx = HttpContext.Current;
        var con = (SqlConnection) ctx.Items["Connection"];
        if (con == null)
        {
            ctx.Items["Connection"] = con = new SqlConnection(ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString);
            ctx.AddOnRequestCompleted(_ => con.Dispose());
        }
        return con;
    }
}