Captcha image in asp.net c#

step 1
download dll mscaptcha to my computer
step 2
Add references from mscaptcha.dll file
step 3
<%@ Register Assembly="MSCaptcha" Namespace="MSCaptcha" TagPrefix="cc1" %>
in aspx file
step 4
<div>
    <cc1:CaptchaControl ID="Captcha1" runat="server"
 CaptchaBackgroundNoise="Low" CaptchaLength="5"
 CaptchaHeight="60" CaptchaWidth="200"
 CaptchaLineNoise="None" CaptchaMinTimeout="5"
 CaptchaMaxTimeout="240" FontColor = "#529E00" />
    </div>
    <asp:TextBox ID="txtCaptcha" runat="server"></asp:TextBox>
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
    <asp:Label ID="lblMessage" runat="server" Text="lblMessage"></asp:Label>
input to the aspx file
step 5
protected void Button1_Click(object sender, EventArgs e)
        {
            try
            {
            Captcha1.ValidateCaptcha(txtCaptcha.Text.Trim());
            if (Captcha1.UserValidated)
            {
                lblMessage.ForeColor = System.Drawing.Color.Green;
                lblMessage.Text = "Valid";
            }
            else
            {
                lblMessage.ForeColor = System.Drawing.Color.Red;
                lblMessage.Text = "InValid";
            }
            }
            catch
            {
                Page_Load(sender,e);
            }
        }
input to cs file

get folder structure asp.net c#

step 1 using System.IO;
step 2
Create Button and traeeview on design view.
step3 create function on cs file.
protected void Button1_Click(object sender, EventArgs e)
        {
            Listdirectory(TreeView1,"D:\\program");
        }

        private void Listdirectory(TreeView treeview,string part)
        {
            treeview.Nodes.Clear();
            var rootdirectoryinfo = new DirectoryInfo(part);
            treeview.Nodes.Add(Createdirtolynode(rootdirectoryinfo));
        }
        private static TreeNode Createdirtolynode(DirectoryInfo directory)
        {
            var directorynote = new TreeNode(directory.Name);
            foreach (var direc in directory.GetDirectories())
            {
                directorynote.ChildNodes.Add(Createdirtolynode(direc));
            }
            foreach (var file in directory.GetFiles())
            {
                directorynote.ChildNodes.Add(new TreeNode(file.Name));
            }
            return directorynote;
        }

Edit file web configuration

step 1
using System.Web.Configuration;
using System.Configuration;
step 2
var configuration = WebConfigurationManager.OpenWebConfiguration("~");
Find file the web config.
var section = (ConnectionStringsSection)configuration.GetSection("connectionStrings");
select tax for editor.
section.ConnectionStrings["MyConnectionString"].ConnectionString = "Data Source=...";
Edit name tax.
configuration.Save();
save file web config.

connection string by ConfigurationManager

step 1
using System.Configuration;

step 2
add string connection string in file webconfig
<add name="default" connectionString="Driver={Microsoft Access Driver (*.mdb)}; DBQ=part-file database;"/>

step 3
create string connection on file cs
public String strcon = ConfigurationManager.ConnectionStrings["default"].ConnectionString;

Exchange-rate by yahoo

step 1
using System.Net;
using System.Text;
using System.Text.RegularExpressions;

step2
create class ConvertCurrency
public static decimal ConvertCurrency(decimal amount, string from, string to)
        {
            try
            {
                WebClient web = new WebClient();
                const string urlPattern = "http://finance.yahoo.com/d/quotes.csv?s={0}{1}=X&f=l1";
                string url = String.Format(urlPattern, from, to);
                string response = new WebClient().DownloadString(url);
                decimal exchangeRate = decimal.Parse(response, System.Globalization.CultureInfo.InvariantCulture);
                return exchangeRate;
            }
            catch (Exception ex)
            {
                return 0;
            }
        }

step 3
core function
decimal apiRate = 0;
            apiRate =Class1.ConvertCurrency(1, "USD", "THB");

sent Email in C#

step 1
using System.Net.Mail
using System.Net

step 2
create mail ,mailto,mail from,mail body,mail subject
MailMessage myMail = new MailMessage();
myMail.From = new MailAddress("info@travexgo.com");
myMail.To.Add(new MailAddress(TextBox4.Text));
myMail.IsBodyHtml = true;
myMail.Subject = "Booking";
myMail.Body ="เนื้อความ"

Step 3
กำหนด Smtp
SmtpClient sm = new SmtpClient("smtp domain");
sm.Port = 25;
sm.Credentials = new NetworkCredential("User", "Password");

Step 4
ทำการส่งโดยใช้ SMTP และ เคลียค่าเมลล์
sm.Send(myMail1);
myMail1 = null;

การใช้งาน Ispostback c#

Ispostback ใช้ในกรณีในการ Refresh หน้าตัวเองหรือกดปุ่ม ที่ runat="server" จะทำให้ IsPostback เป็น True แต่ถ้าเป็นการเรียกหน้านั้นครั้งแรก Ispostback จะเป็นค่า false
ตัวอย่าง
if (IsPostBack)
            {
                condition += check_sqlcondition(var_search_cabin_class, var_search_form, "", "", "");
            }