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How to create a simple Http Server in NodeJs

Node.js is an open source, cross-platform runtime environment for server-side and networking applications. Node.js applications are written in JavaScript and can be run within the Node.js runtime on OS X, Microsoft Windows, Linux.Node.js uses the Google V8 JavaScript engine to execute code, and a large percentage of the basic modules are written in JavaScript. Node.js contains a built-in library to allow applications to act as a Web server without software such as Apache HTTP Server or IIS.
In this post I will show you how to create a simple Http Server using node.js Before diving into code let us first install node.js from following link.https://nodejs.org/Once the node.js installed.Open the terminal window and type following command.node –versionIf you see similar output then node.js is installed on your machine.Open any text editor and paste following code into it and save it as Sever.js.var http = require("http"); function requestHandler(req, res) { res.writeHead(200, …

Convert colum to row without using unpivot operator

In this post I will show you how to convert column to row in SQL.For this post I am going to use following table which have three colum stu_name,sibject and marks.SELECT stu_name, MAX(CASE WHEN subject = 'ECO' THEN marks ELSE 0 END) ECO, MAX(CASE WHEN subject = 'HIS' THEN marks ELSE 0 END) HIS, MAX(CASE WHEN subject = 'MAT' THEN marks ELSE 0 END) MAT, MAX(CASE WHEN subject = 'GEO' THEN marks ELSE 0 END) GEO, MAX(CASE WHEN subject = 'SCI' THEN marks ELSE 0 END) SCI FROM col_to_rows GROUP BY stu_name

How to implement Stack using linked list

Stacks are easier to implement using linked lists. There is no need to set a limit on the size of the stackusing System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace LinkedlistUsingStack { public class Node { public int Data { get; set; } public Node Next { get; set; } public Node(int data) { this.Data = data; } } public class Stack { private Node _stackTop; public void Push(int newValue) { Node newNode = new Node(newValue); newNode.Next = _stackTop; _stackTop = newNode; } public bool IsEmpty() { return _stackTop == null; } public int Pop() { Node temp = _stackTop; var data = temp.Data; _stackTop = temp.Next; return data; } public void Print() { …

How to Find if Linked List contains Loops or Cycles in C#

In this post I will show you how to detect loop in linked list.We can find the loop in the linked list via Floyd’s Cycle-Finding Algorithm, explained here.The algorithm is pretty straightforward: We start at the beginning of the linked list with two pointers. The first pointer is incremented through each node of the list. The second pointer moves twice as fast, and skips every other node. If the linked list contains a loop, these two pointers will eventually meet at the same node, thus indicating that the linked list contains a loop. .using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Algo { public class Node { public Node Next { get; set; } public int Value { get; set; } public Node(int value) { this.Value = value; } } public class LinkedList { private Node _head; public LinkedList() { } public vo…

Reverse a given linked list in c#

In this post I will show you how to reverse a  given linked list in c#.For example a given linked list as show below10->20->30-NULLthen output should be30->20->10-NULLusing System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Algo { public class List { public List Next { get; set; } public int Value { get; set; } public List(int value) { Value = value; } public override string ToString() { List current = this; StringBuilder builder = new StringBuilder(); while (current!=null) { builder.Append(current.Value + "->"); current = current.Next; } return builder.ToString(); } public List ReverseList() { List prev = null; List next = null; List current = this; …

How to check a tree is a binary tree of not

This is continuation of my post How to create binary tree in c#.In this post I will show you how to check a given tree is a binary tree or not. public bool isBST() { return (IsBST(_root)); } private bool IsBST(Node node) { if (node == null) return (true); // do the subtrees contain values that do not // agree with the node? if (node.Left != null && FindMaxValue(node.Left) > node.Data) return (false); if (node.Right != null && FindMinValue(node.Right) <= node.Data) return (false); // check that the subtrees themselves are ok return (IsBST(node.Left) && IsBST(node.Right)); }

Mirror of a binary tree

This is continuation of my post How to create binary tree in c#.In this post I will show you how convert a given binary tree into it’s mirror image./**
Changes the tree into its mirror image. So the tree...
       4
      / \
     2   5
    / \
   1   3 is changed to...
       4
      / \
     5   2
        / \
       3   1Strategy:Uses a recursive helper that recurs over the tree, swapping the left/right pointers. public void MirrorTree() { MirrorTree(_root); } private void MirrorTree(Node node) { if (node != null) { // do the sub-trees MirrorTree(node.Left); MirrorTree(node.Right); // swap the left/right pointers Node temp = node.Left; node.Left = node.Right; node.Right = temp; } }

How to print out all path from root to leaf of a given binary tree

This is continuation of my post How to create binary tree in c#.In this post I will show you how to print all path from root to leaf of a given binary tree in c#.Let’s consider following binary tree.             *       4
             *    2     5
             *  1    3     For above tree there are three path from root to leafPath 1 : 4 2 1Path 2: 4 2 3Path 3: 4 5 public void PrintPath() { int[] path = new int[100]; printPaths(_root, path, 0); } private void printPaths(Node node, int[] path, int pathLen) { if (node == null) return; // append this node to the path array path[pathLen] = node.Data; pathLen++; // it's a leaf, so print the path that led to here if (node.Left == null && node.Right == null) { PrintArray(path, pathLen); } else { // otherwise try both subtre…

Given a binary tree, find path sum

Given a tree and a sum, returns true if there is a path from the root  down to a leaf, such that adding up all the values along the path  equals the given sum.let’s consider the following binary tree as an example and path sum value is 9.        4
      / \
     2   5
    / \
   1   3Root-to-leaf paths:
   path 1: 4 2 1
   path 2: 4 2 3
   path 3: 4 5You can see that there are two path that gives sum 9 (Path2 and Path 3).Traverse the tree from root to leaves in top down fashion and subtract the node value from the sum  and check to see if the sum is 0 when you run out of tree. public bool HasPathSum(int sum) { return HasPathSum(_root, sum); } private bool HasPathSum(Node root, int sum) { // return true if we run out of tree and sum==0 if (root == null) return sum == 0; else { int subSum = sum - root.Data; return ( HasPathSum(root.L…

How to find min or max value in a given binary tree

This is continuation of my post How to create binary tree in c#.In this post I will show you how to find max or min value in a given binary tree.Min Value: Loop down to find the leftmost leaf Max Value: Loop down to find the rightmost leaf public int FindMinValue() { return FindMinValue(_root); } private int FindMinValue(Node root) { if (root == null) return -1; else { Node current = root; while (current.Left!=null) { current = current.Left; } return current.Data; } } public int FindMaxValue() { return FindMaxValue(_root); } private int FindMaxValue(Node root) { if (_root == null) return -1; else { Node current = root; while (curre…

How to calculate max depth of given binary tree in c#

This is continuation of my post How to create binary tree in c#.In this post I will show you how to calculate max depth of a given binary tree in c#.MaxDepth of a tree -- the number of nodes along the longest path from the root node down to the farthest leaf node. public int MaxDepth() { return MaxDepth(_root); } private int MaxDepth(Node root) { if (root == null) return -1; // compute the depth of each subtree else { int leftDepth = MaxDepth(root.Left); int rightDepth = MaxDepth(root.Right); //Return max of left or right tree. return 1 + Math.Max(leftDepth, rightDepth); } }

How to calculate size of binary tree

This is continuation of my post How to create binary tree in c# .In this post I will show you how to find size of binary tree.Size of binary tree is number of nodes in a given tree.Following is the recursive implementation of size function //Compute the number of nodes in a tree. public int Size() { return Size(_root); } private int Size(Node root) { if (root == null) return 0; return 1 + Size(root.Left) + Size(root.Right); }

How to create binary tree in c#

A binary tree is made of nodes, where each node contains a "left" pointer, a "right" pointer, and a data element. The "root" pointer points to the topmost node in the tree. The left and right pointers recursively point to smaller "subtrees" on either side. A null pointer represents a binary tree with no elements -- the empty tree. The formal recursive definition is: a binary tree is either empty (represented by a null pointer), or is made of a single node, where the left and right pointers (recursive definition ahead) each point to a binary tree. Implementationusing System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace BTree { public class Node { public int Data { get; set; } public Node Left { get; set; } public Node Right { get; set; } public Node() { } public Node(int data) { this.Data = data;…

How to create instance of generic class using reflection

In this post I am going to show how to create instance of generic class using c# reflection.The trick is to use the MakeGenericType to make the argument(s) and then call create Instance. Here is a code snippet:Type d1 = typeof(List<>); Type[] typeArgs = { typeof(string) }; Type makeme = d1.MakeGenericType(typeArgs); object o = Activator.CreateInstance(makeme); List<string> itsMe = o as List<string>;

How to host wcf service in IIS using Tcp protocol

In this post I am going to show you how to host WCF service in IIS using TCP protocol.By default, the TCP WCF activation service is not enabled on your machine. You can follow these steps to enable the TCP activation for WCF services:
Go to Control Panel | Programs | Turn Windows features on or off. Expand the Microsoft .Net Framework 3.5.1 node on Windows 7 Check the checkbox for Windows Communication Foundation Non-HTTP Activation on Windows 7
Next,Create the IIS application to host the WCF application using TCP protocol.Follow these steps
Open run command and type inetmgrCreate a new application and point to physical folder.Select the DefaultAppPoll  and make sure your default app pool is a .NET 4.0.X application pool.Right-click on web application, select Manage Application | Advanced Settings, and then add net.tcp to Enabled Protocols.(Make sure you use all lowercase letters and separate it from the existing HTTP protocol with a comma)
Now the service is hosted in IIS using th…

Todo App using Web API and Knockout

In this post I am going to show you how to develop a todo app using knockoutjs and microsoft Web API.What is knockoutjs”Knockout is a standalone JavaScript implementation of the Model-View-ViewModel pattern with templates. The underlying principles are therefore: a clear separation between domain data, view components and data to be displayed.”-WikipediaKnockout is built around three core features: Observables and dependency tracking Declarative bindings Templating Before diving to example code first go through the following http://knockoutjs.com/documentation/observables.html#mvvm_and_view_modelsOpen visual studio and create a new Web API applicationOpen Package Manager console and install knockoutjs as shown in below imageRight click the Model folder and add a new class named TodoItem and paste following code. public class TodoItem { public int Id { get; set; } public string Title { get; set; } public bool Done { get; set; } }Right click the model f…

How to enable CORS in web API2

In this post I am going to show you a very simple and useful tips that how to enable CORS in web API2.
What is CORS
Cross-origin resource sharing (CORS) is a mechanism that allows many resources (e.g. fonts, JavaScript, etc.) on a web page to be requested from anotherdomain outside the domain from which the resource originated
How to enable in CORS in web API2
In Visual Studio, from the Tools menu, select Library Package Manager, then select Package Manager Console. In the Package Manager Console window, type the following command:Install-Package Microsoft.AspNet.WebApi.Cors Open the file App_Start/WebApiConfig.cs. Add the following code to the WebApiConfig.Register method.
public static void Register(HttpConfiguration config) { // New code config.EnableCors(); config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RoutePa…

How to convert DataSet to List

In this post I am going to show you a very useful c# code snippet that convert DataSet to List<T>. public static List<T> ToCollection<T>(this DataTable dt) { List<T> lst = new List<T>(); Type tClass = typeof(T); PropertyInfo[] pClass = tClass.GetProperties(); List<DataColumn> dc = dt.Columns.Cast<DataColumn>().ToList(); T cn; foreach (DataRow item in dt.Rows) { cn = (T)Activator.CreateInstance(tClass); foreach (PropertyInfo pc in pClass) { DataColumn d = dc.Find(c => c.ColumnName == pc.Name); if (d != null) { if (item[pc.Name] != DBNull.Value) { pc.SetValue(cn, (item[pc.Name]), null); } } } …

Self host web API

In this post I will show you how to create web api that run outside IIS application.
Open visual studio and create a console application

Add the Web API and OWIN Packages From the Tools menu, click Library Package Manager, then click Package Manager Console. In the Package Manager Console window, enter the following command:
Install-Package Microsoft.AspNet.WebApi.OwinSelfHost

Right click  the project and add new class named Startup.cs and add following code snippet in it
public class Startup { // This code configures Web API. The Startup class is specified as a type // parameter in the WebApp.Start method. public void Configuration(IAppBuilder appBuilder) { // Configure Web API for self-host. HttpConfiguration config = new HttpConfiguration(); config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", default…

How to create Fibonacci series using Linq

In this post I am going to show you how to generate fiboancci number series using Linq.What is Fibonacci series : The Fibonacci Sequence is the series of numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ... The next number is found by adding up the two numbers before it. public static IEnumerable<int> Fib(int n) { List<int> fibs = new List<int>(); Enumerable.Range(0, n) .ToList() .ForEach(f => fibs.Add((f <= 1 ? 1 : fibs[f - 2] + fibs[f - 1]))); return fibs; }

How to create chat application using microsoft asp.net signalr

open visual studio and create a new MVC application
Select Empty MVC application

Open Package Manager Console and install SignalR

Right click on project and add new class ChatHub and inherit from Hub class that resides in Microsoft.AspNet.SignalR

public class ChatHub:Hub { //this method is called when client send message public void sendMessage(string message) { //this method brodcast message to all connected client Clients.All.newMessage(message); } } Right click on project and add new class named Startup and add following code inside it
public class Startup { public void Configuration(IAppBuilder app) { app.MapSignalR(); } } Create a new html page and add following markup inside it.You can see that I have added three JavaScript lib :jquery,jqery-signalr* and  signalr/hubs.Signalr/hubs contains functions for interacting with server side hub class and also it generated automatic…

Access to the Hubs from outside of the Hub class

The Clients dynamic property of the Hub gives you access to all clients connected to the hub within the hub class. However, what if you would like to push data to the clients from outside of the Hub class.Use following code snippet and replace HubClass with your own class and get access of the signalr clients and server dynamic properties/methods.var myHub = GlobalHost.ConnectionManager.GetHubContext<HubClass>();

Compare Linq and Ruby Part1

Linq Where equivalent in RubyOne of the most used (just guessing) LINQ methods would be Where(), in .NET allows you to provide a Lambda that is used to filter a collection of objects var ints = new[] { 13, 42, 96, 2, 83 }; var evens = ints.Where(x = > x % 2 == 0); foreach(int i in evens) { Console.WriteLine(i); }And in Ruby this functionality would be achieved with select.ints = [13, 42, 96, 2, 83] evens = ints.select { | x | x % 2 == 0 } puts evensLinq OrderBy expression equivalent in RubyTo sort a sets of elements in c# with Linq we use OrderByvar words = new[] { "Perl", "c#", "ruby", "java" }; var ordered = words.OrderBy(x = > x); ordered.ToList().ForEach(Console.WriteLine);And in Ruby this functionality would be achieved with sort. words = ["Perl", "c#", "ruby", "java"] ordered = words.sort puts orderedLinq Select expression equivalent in RubyIn .NET to convert a set of items to anot…

How to post data using HttpClient

In this post I will show you how to post data to web api using HttpClient.

privatestatic async Task PostJSON() { HttpClient httpClient = new HttpClient(); HttpContent content = new StringContent(@"{ ""Username"": """ + "etc." + @"""}"); content.Headers.ContentType = new MediaTypeHeaderValue("application/json"); HttpResponseMessage response = await httpClient.PostAsync("http://myapi.com/authentication", content); string statusCode = response.StatusCode.ToString(); } /// <summary>/// Post Key/Value/// </summary>/// <returns></returns>privatestatic async Task Post() { HttpClient client = new HttpClient(); var values = new Dictionary<string, string>(); values.Add("author", "santosh"); values.Add(…