Advanced Computer Programming : In Memory Search using Lamda Expression: Realtime Chat application on web in ASP.Net: Step 4

Welcome at Realtime Chat application on web in ASP.Net using SignalR technology. This is step 4 and now we will learn how we can search in memory array without any loop like for, while etc. We will use Lamda expression to search an element in array list with generics. I shall not describe about these technologies from theoretical perspective, here I shall show some application of these. You can read theory of these things from MSDN site.

You may think why this is require for our chat application, really good question. We shall use this technique to find an online user in server. However we can take database help to find online users but to minimize database operation I have used this technique. In chat application I have used a public static list (array) to hold online users, and from here I am searching users to generate online friend lists. By that way I have minimize a lot database operation and this technique can improve your chat application.

Lets check the code first then shall describe the codes.

HTML/ASP.Net part

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <h1>In memory search using Lamda Expression in C#.Net</h1>
        <h3>Search country calling code</h3>
        <p>
            Country Name:
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
 <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Find Calling Code" />
        </p>
        <p>
            <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
        </p>
        <a href="http://en.wikipedia.org/wiki/List_of_country_calling_codes" target="_blank">Full list is available here</a>
    </form>
</body>
</html>

and the C# code as below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        FindCallingCode();
    }
    private void FindCallingCode()
    {
        //In real use databind before searching, using by that way as demo
        List<Country> countries = new List<Country>();
        countries.Add(new Country { callingCode = "+91", name = "India" });
        countries.Add(new Country { callingCode = "+44", name = "UK" });
        countries.Add(new Country { callingCode = "+1", name = "USA" });
        countries.Add(new Country { callingCode = "+88", name = "Bangladesh" });
        countries.Add(new Country { callingCode = "+49", name = "Germany" });
        countries.Add(new Country { callingCode = "+33", name = "France" });
        countries.Add(new Country { callingCode = "+55", name = "Brazil" });

        Country country = countries.FirstOrDefault(x => x.name.ToLower() == TextBox1.Text.Trim().ToLower());
        if (country != null)
            Label1.Text = "Calling code of " + country.name + " is " + country.callingCode;
        else
            Label1.Text = TextBox1.Text + " Not Found in our Country List";
    }
}
public class Country {
    public string callingCode { get; set; }
    public string name { get; set; }
}

Here is main method is "FindCallingCode()" and class "Country". Here I am doing all operations. Lets look at some important code.

Country class: This class I have defined to create country objects which will store country name and calling code. If you need extra properties you can add these easily.

List<Country> countries = new List<Country>();

In the above code I have defined a list (array) of county objects with name countries. Naming convention using as this variable holding multiple country hence its plural name of country.

countries.Add(new Country { callingCode = "+91", name = "India" });

In the above line of code I have adding element of array by creating country class object.

Country country = countries.FirstOrDefault(x => x.name.ToLower() == TextBox1.Text.Trim().ToLower());

This is actually Lamda expression "x=>x.name" this is doing searching operation with method "FirstOrDefault". This line searching all element and doing comparison with user entered country name and stored country name. When matched it will return the country object.

Label1.Text = "Calling code of " + country.name + " is " + country.callingCode;

In previous line of code we have found country object from array of countries and now getting calling code and name from the found object.

In my chat application I have used mainly this (FirstOrDefault) method and for some cases have used "Count", "Find" methods/properties. "Find" and "FirstOrDefault" both can do a bit similar work but "Find" is very fast (in a blog I found 1000 times) than "FirstOrDefault", hence I am using as and when these are suitable.
For your knowledge you can check other methods as well.

Thanks for reading my blog please visit again for next article.

Source code is available here.

Advanced Computer Programming

Tuesday, February 25, 2014

In Memory Search using Lamda Expression: Realtime Chat application on web in ASP.Net: Step 4

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