Generate random Persian number for captcha using C# and VB.Net in ASP.Net

Hi nedash,

Refer below code.

HTML

<asp:Label ID="lblID" runat="server" />

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    generateStopSpamText();
}

private void generateStopSpamText()
{
    string firstNumber = GenerateRandomPersianNumber();
    System.Threading.Thread.Sleep(100);
    string secondNumber = GenerateRandomPersianNumber();

    ViewState["spam"] = Convert.ToInt16(PersianToEnglish(firstNumber)) + Convert.ToInt16(PersianToEnglish(secondNumber));
    lblID.Text = firstNumber + " + " + secondNumber;
}

private string[] persion = { "۰", "۱", "۲", "۳", "۴", "۵", "۶", "۷", "۸", "۹" };
private string[] english = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
public string PersianToEnglish(string strNum)
{
    string chash = strNum;
    for (int i = 0; i < 10; i++)
    {
        chash = chash.Replace(persion[i], english[i]);
    }
    return chash;
}

protected string GenerateRandomPersianNumber()
{
    string numbers = "۱۲۳۴۵۶۷۸۹";
    string characters = numbers;
    string id = string.Empty;
    for (int i = 0; i < 1; i++)
    {
        string character = string.Empty;
        do
        {
            int index = new Random().Next(0, characters.Length);
            character = characters.ToCharArray()[index].ToString();
        } while (id.IndexOf(character) != -1);
        id += character;
    }
    return id;
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    generateStopSpamText()
End Sub

Private Sub generateStopSpamText()
    Dim firstNumber As String = GenerateRandomPersianNumber()
    Threading.Thread.Sleep(100)
    Dim secondNumber As String = GenerateRandomPersianNumber()
    ViewState("spam") = Convert.ToInt16(PersianToEnglish(firstNumber)) + Convert.ToInt16(PersianToEnglish(secondNumber))
    lblID.Text = firstNumber & " + " & secondNumber
End Sub

Private persion As String() = {"۰", "۱", "۲", "۳", "۴", "۵", "۶", "۷", "۸", "۹"}
Private english As String() = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"}

Public Function PersianToEnglish(ByVal strNum As String) As String
    Dim chash As String = strNum
    For i As Integer = 0 To 10 - 1
        chash = chash.Replace(persion(i), english(i))
    Next

    Return chash
End Function

Protected Function GenerateRandomPersianNumber() As String
    Dim numbers As String = "۱۲۳۴۵۶۷۸۹"
    Dim characters As String = numbers
    Dim id As String = String.Empty
    For i As Integer = 0 To 0
        Dim character As String = String.Empty
        Do
            Dim index As Integer = New Random().Next(0, characters.Length)
            character = characters.ToCharArray()(index).ToString()
        Loop While id.IndexOf(character) <> -1

        id += character
    Next

    Return id
End Function