using System.Net.Sockets;  
using System.IO;  
using System.Text;
using System.Web;
public partial class _Default: System.Web.UI.Page {  
  protected void btnCheck_Click(object sender, EventArgs e) {  
    TcpClient tClient = new TcpClient("gmail-smtp-in.l.google.com", 25);  
    string CRLF = "\r\n";  
    byte[] dataBuffer;  
    string ResponseString;  
    NetworkStream netStream = tClient.GetStream();  
    StreamReader reader = new StreamReader(netStream);  
    ResponseString = reader.ReadLine();  
    /* Perform HELO to SMTP Server and get Response */  
    dataBuffer = BytesFromString("HELO KirtanHere" + CRLF);  
    netStream.Write(dataBuffer, 0, dataBuffer.Length);  
    ResponseString = reader.ReadLine();  
    dataBuffer = BytesFromString("MAIL FROM:<[email protected]>" + CRLF);  
    netStream.Write(dataBuffer, 0, dataBuffer.Length);  
    ResponseString = reader.ReadLine();  
    /* Read Response of the RCPT TO Message to know from google if it exist or not */  
    dataBuffer = BytesFromString("RCPT TO:<" + TextBox1.Text.Trim() + ">" + CRLF);  
    netStream.Write(dataBuffer, 0, dataBuffer.Length);  
    ResponseString = reader.ReadLine();  
    if (GetResponseCode(ResponseString) == 550) {  
      Response.Write("Mai Address Does not Exist !<br/><br/>");  
      Response.Write("<B><font color='red'>Original Error from Smtp Server :</font></b>" + ResponseString);  
    }  
    /* QUITE CONNECTION */  
    dataBuffer = BytesFromString("QUITE" + CRLF);  
    netStream.Write(dataBuffer, 0, dataBuffer.Length);  
    tClient.Close();  
  }  
  
  private byte[] BytesFromString(string str) {  
    return Encoding.ASCII.GetBytes(str);  
  }  
  
  private int GetResponseCode(string ResponseString) {  
    return int.Parse(ResponseString.Substring(0, 3));  
  }  
}  

C Sharp Online Compiler

Write, Run & Share C# code online using OneCompiler's C# online compiler for free. It's one of the robust, feature-rich online compilers for C# language, running on the latest version 8.0. Getting started with the OneCompiler's C# compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C# and start coding.

Read inputs from stdin

OneCompiler's C# online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

using System;
 
namespace Sample
{
  class Test
    {
      public static void Main(string[] args)
       {
         string name;
         name = Console.ReadLine();
         Console.WriteLine("Hello {0} ", name);
	}
     }
}

About C Sharp

C# is a general purpose object-oriented programming language by Microsoft. Though initially it was developed as part of .net but later it was approved by ECMA and ISO standards.

You can use C# to create variety of applications, like web, windows, mobile, console applications and much more using Visual studio.

Syntax help

Data types

Data TypeDescriptionRangesize
intTo store integers-2,147,483,648 to 2,147,483,6474 bytes
doubleto store large floating point numbers with decimalscan store 15 decimal digits8 bytes
floatto store floating point numbers with decimalscan store upto 7 decimal digits4 bytes
charto store single characters-2 bytes
stringto stores text-2 bytes per character
boolto stores either true or false-1 bit

Variables

Syntax

datatype variable-name = value;

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition or set of few conditions IF-ELSE is used.

if(conditional-expression) {
   // code
} 
else {
   // code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement) {
  // code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

data-type[] array-name;

Methods

Method is a set of statements which gets executed only when they are called. Call the method name in the main function to execute the method.

Syntax

static void method-name() 
{
  // code to be executed
}