Convert integer to parsian and display in Label in ASP.Net

hi

I used label in page that will show number...

<asp:Label ID="LblPostS" runat="server" CssClass="lblhazineST1">4000</asp:Label>

I want show number in persian with below code:

   public string toPersianNumber(string input)
    {
        string[] persian = new string[10] { "۰", "۱", "۲", "۳", "۴", "۵", "۶", "۷", "۸", "۹" };
        for (int j = 0; j < persian.Length; j++)
        {
            input = input.Replace(j.ToString(), persian[j]);
        }
        return input;

    }

how I can use above metod for label?

Best regards

neda