U+202A:   LEFT-TO-RIGHT EMBEDDING (LRE) 
U+202B:   RIGHT-TO-LEFT EMBEDDING (RLE) 
U+202D:   LEFT-TO-RIGHT OVERRIDE (LRO) 
U+202E:   RIGHT-TO-LEFT OVERRIDE (RLO) 
U+202C:   POP DIRECTIONAL FORMATTING (PDF) 

using System;
using System.Diagnostics;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace RleTests
{
    class Program
    {
        const char RightToLeftEmbedding = (char)0x202B;
        const char PopDirectionalFormatting = (char)0x202C;

        static string FixWeakCharacters(string data)
        {
            if (string.IsNullOrWhiteSpace(data)) return string.Empty;
            var weakCharacters = new[] { @"\", "/", "+", "-", "=", ";", "$" };
            foreach (var weakCharacter in weakCharacters)
            {
                data = data.Replace(weakCharacter, RightToLeftEmbedding + weakCharacter + PopDirectionalFormatting);
            }
            return data;
        }

        static void Main(string[] args)
        {
            using (var pdfDoc = new Document(PageSize.A4))
            {
                PdfWriter.GetInstance(pdfDoc, new FileStream("Test.pdf", FileMode.Create));
                pdfDoc.Open();

                FontFactory.Register("c:\\windows\\fonts\\Arial.ttf");
                Font tahoma = FontFactory.GetFont("Arial", BaseFont.IDENTITY_H);

                var table1 = new PdfPTable(1);
                table1.WidthPercentage = 100;

                var pdfCell = new PdfPCell
                {
                    RunDirection = PdfWriter.RUN_DIRECTION_RTL,
                    Border = 0,
                    Phrase = new Phrase(FixWeakCharacters(
                        "تاریخ: " + "1390/11/18" + Environment.NewLine +
                        "شماره پروژه: " + "1/2/3/4/56" + Environment.NewLine +
                        "اسلش: " + " 12/A/13 " + Environment.NewLine +
                        "بک اسلش: " + "  12\\13\\14 " + Environment.NewLine +
                        "مساوی و جمع: " + " 2+3=5 " + Environment.NewLine +
                        "سمی کولون: " + " 2=1+1; " + Environment.NewLine +
                        "دلار: " + "12$" + Environment.NewLine +
                        "کاما: " + "12,34,67" + Environment.NewLine +
                        "نقطه: " + "12.34" + Environment.NewLine +
                        "پرانتز: " + "متن (ساده)"
                        ),
                        tahoma)
                };

                table1.AddCell(pdfCell);
                pdfDoc.Add(table1);

            }

            Process.Start("Test.pdf");
        }
    }
}

<span dir="ltr" style="display:inline">1390/11/19</span>

U+202A:   LEFT-TO-RIGHT EMBEDDING (LRE) 
U+202B:   RIGHT-TO-LEFT EMBEDDING (RLE) 
U+202D:   LEFT-TO-RIGHT OVERRIDE (LRO) 
U+202E:   RIGHT-TO-LEFT OVERRIDE (RLO) 
U+202C:   POP DIRECTIONAL FORMATTING (PDF) 

using System;
using System.Diagnostics;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace RleTests
{
    class Program
    {
        const char RightToLeftEmbedding = (char)0x202B;
        const char PopDirectionalFormatting = (char)0x202C;

        static string FixWeakCharacters(string data)
        {
            if (string.IsNullOrWhiteSpace(data)) return string.Empty;
            var weakCharacters = new[] { @"\", "/", "+", "-", "=", ";", "$" };
            foreach (var weakCharacter in weakCharacters)
            {
                data = data.Replace(weakCharacter, RightToLeftEmbedding + weakCharacter + PopDirectionalFormatting);
            }
            return data;
        }

        static void Main(string[] args)
        {
            using (var pdfDoc = new Document(PageSize.A4))
            {
                PdfWriter.GetInstance(pdfDoc, new FileStream("Test.pdf", FileMode.Create));
                pdfDoc.Open();

                FontFactory.Register("c:\\windows\\fonts\\Arial.ttf");
                Font tahoma = FontFactory.GetFont("Arial", BaseFont.IDENTITY_H);

                var table1 = new PdfPTable(1);
                table1.WidthPercentage = 100;

                var pdfCell = new PdfPCell
                {
                    RunDirection = PdfWriter.RUN_DIRECTION_RTL,
                    Border = 0,
                    Phrase = new Phrase(FixWeakCharacters(
                        "تاریخ: " + "1390/11/18" + Environment.NewLine +
                        "شماره پروژه: " + "1/2/3/4/56" + Environment.NewLine +
                        "اسلش: " + " 12/A/13 " + Environment.NewLine +
                        "بک اسلش: " + "  12\\13\\14 " + Environment.NewLine +
                        "مساوی و جمع: " + " 2+3=5 " + Environment.NewLine +
                        "سمی کولون: " + " 2=1+1; " + Environment.NewLine +
                        "دلار: " + "12$" + Environment.NewLine +
                        "کاما: " + "12,34,67" + Environment.NewLine +
                        "نقطه: " + "12.34" + Environment.NewLine +
                        "پرانتز: " + "متن (ساده)"
                        ),
                        tahoma)
                };

                table1.AddCell(pdfCell);
                pdfDoc.Add(table1);

            }

            Process.Start("Test.pdf");
        }
    }
}

<span dir="ltr" style="display:inline">1390/11/19</span>

        public static void InitializeDb(this IServiceProvider serviceProvider)
        {
            var scopeFactory = serviceProvider.GetRequiredService<IServiceScopeFactory>();
            using (var scope = scopeFactory.CreateScope())
            {
                var identityDbInitializer = scope.ServiceProvider.GetService<IIdentityDbInitializer>();
                identityDbInitializer.Initialize();
                identityDbInitializer.SeedData();
            }
        }

[TestMethod]
public void TestRandomWithEnumerable()
{
    var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    var random = new Random();
    var result = new string(
        Enumerable.Repeat(chars, 6)
        .Select(s => s[random.Next(s.Length)])
        .ToArray());
    Assert.IsTrue(result.Length == 6);
}

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuwxyz~!@#$%^&*";

Guid.NewGuid().ToString().Replace("-", string.Empty).Substring(0, 6);

Guid.NewGuid().ToString("n").Substring(0, 6);

public static string GetUniqueKey(int maxSize)
        {
            char[] chars = new char[62];
            chars =
            "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".ToCharArray();
            byte[] data = new byte[1];
            using (RNGCryptoServiceProvider crypto = new RNGCryptoServiceProvider())
            {
                crypto.GetNonZeroBytes(data);
                data = new byte[maxSize];
                crypto.GetNonZeroBytes(data);
            }
            StringBuilder result = new StringBuilder(maxSize);
            foreach (byte b in data)
            {
                result.Append(chars[b % (chars.Length)]);
            }
            return result.ToString();
        }
    }

public string Get8CharacterRandomString()
{
    string path = Path.GetRandomFileName();
    path = path.Replace(".", ""); // Remove period.
    return path.Substring(0, 6);  // Return 6 character string
}

var chars = "abcdefghijklmnopqrstuvwxyz123456789".ToArray();
string pw = Enumerable.Range(0, passwordLength)
                      .Aggregate(
                          new StringBuilder(),
                          (sb, n) => sb.Append((chars[random.Next(chars.Length)])),
                          sb => sb.ToString());

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="AjaxTest.aspx.cs" Inherits="testWebForms87.AjaxTest" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>jQuery Ajax Text</title>

<script src="jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
    $(document).ready(function() {
        $("#<%= TextBox1.ClientID %>").blur(function(event) {
            $.ajax({
                type: "POST",
                url: "AjaxTest.aspx/IsUserAvailable",
                data: "{'username': '" + $('#<%= TextBox1.ClientID %>').val() + "'}",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function(msg) {
                    $('#valid').html("<img src='ajaxImages/waiting.gif' alt='لطفا کمی تامل کنید'>");
                    var delay = function() {
                        AjaxSucceeded(msg);
                    };

                    setTimeout(delay, 2000); //remove this
                },
                error: AjaxFailed
            });
        });
    });
    function AjaxSucceeded(result) {
        if (result.d == true)
            $('#msg').html("<img src='ajaxImages/available.gif' alt='نام کاربری درخواستی موجود است'>");
        else
            $('#msg').html("<img src='ajaxImages/taken.gif' alt='متاسفانه نام کاربری مورد نظر پیشتر دریافت شده‌است'>");
    }
    function AjaxFailed(result) {
        alert(result.status + ' ' + result.statusText);
    }
</script>

</head>
<body>
<form id="form1" runat="server">
<div>
    user name:
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <span id="msg"></span>
    <br />
    pass:
    <asp:TextBox ID="TextBox2" TextMode="Password" runat="server"></asp:TextBox>
</div>
<!-- preload -->
<div style="display: none">
    <img src="ajaxImages/available.gif" alt="available" />
    <img src="ajaxImages/taken.gif" alt="taken" />
    <img src="ajaxImages/waiting.gif" alt="waiting" />
</div>
</form>
</body>
</html>

using System;
using System.Web.Services;

namespace testWebForms87
{
public partial class AjaxTest : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    [WebMethod]
    public static bool IsUserAvailable(string username)
    {
        // این مورد را با خواندن اطلاعات از دیتابیس می‌شود تعویض کرد
        return username != "test";
    }
}
}

type: "POST"

url: "AjaxTest.aspx/IsUserAvailable"

data: "{'username': '" + $('#<%= TextBox1.ClientID %>').val() + "'}",

contentType: "application/json; charset=utf-8",

dataType: "json",

<xx yy="nn"></xx>

{ "xx": {"yy":"nn"} }

success: function(msg)

error: AjaxFailed