Today we will discuss about the root of ASP.NET 5, which is WWWroot. When you take a closer look at the ASP.NET 5 project, you will see that there are many things which are carry forwarded like Model, View, Controller, clean separation of concerns and may more.

But, there are also some significant changes around ASP.NET 5. Now, the root of the website is no longer the root of the project. By default, root will be WWWroot folder. The idea behind this to maintain the clean separation between the files at the web-server retrieved and sent to the client and the files which contains the logic and configuration. Static files like JS, CSS, HTMLs can live in WWWroot folder.

Now, lets suppose when i run the app and tried to see the image which i have placed in My Imgaes folder, then it will give me 404 error. On the other hand, if i go ahead and add the same folder in WWWroot folder and try to navigate the same then it will produce me the result.

so, the point is all static files are served by root folder and logical stuffs served by project space as we initially saw, when i added controller in the controller’s folder and it took effect. One more thing you might have observed that there is no web.config file now in the solution. Also now there is no Global.asax file; however the same is replaced by startup.cs file. But, we’ll see this later. 1st let’s see project.json file. This file now manages many aspects of website.

First thing which you will notice here that root folder is set to WWWroot here. So, this is the place which is telling website that this is the root folder. So begin the show from here. This you can change as well or rename if you like to. Now, this configuration file is in JSON format. This is also telling the ASP.NET runtime what dependencies project is going to need. In this new ASP.NET 5 system there is a new way to manage dependencies. No need to reference assemblies and store the lists of referenced assemblies in the project file. Instead we refer to nuget packages as dependencies and these dependencies are listed in our project.json file. Now, there are couple of reasons for this change. One reason is to simplify the dependency management. Another good reason for this is that ASP.NET is moving away from VS dependency. So, in future i can use any text editor to build the ASP.NET App.

Now, these dependencies can be both the ways. One way which we used already shown below in the screen shot.

Now, the UI of this also changed. Initially we used to have Modal window. Now, this is more like complete screen giving wider visibility. I can also see the installed templates like

Also, i still have the flexibility of different nuget source. 2nd Option is via project.json file. Let’s suppose i am planning to install some custom package. Then i can do like shown below as well

However, whatever package you install; you can find its references under “References“. Below, in the screen shot you can see that there are two versions of runtime here. 1st one is the core version and 2nd one is the cloud optimized version.

Let’s collapse the same and drill into it. Now, here dependency management system will keep your assemblies in nice tree structure. So, it nicely tells which package are dependent on which package.

Now, as far as Framework and runtime is concerned as you can see below in the screen shot; i have both frameworks listed here.

So, whenever i am building the solution i am building against both of these frameworks. By building against both i am actually ensuring that it will work well against both the frameworks. This also means whenever i am switching platform my code won’t break there.

But, let’s go ahead and break something here. You remember in the last segment i created one new controller with a notepad. Now, let’s modify the same and refresh the app.

As you can see that it says that GetCallingAssembly() which is part of System.Reflection is not supported in the cloud optimized version. But, let’s suppose i overlooked this error and refresh the app.So, it actually produced me desired result.

But, when i explicitly build the project and checked the output window, then it gave me below error message.

So, building with error but application is working fine with full blown CLR. Now, if you have decided that you don’t want CORE CLR version. so, you can just comment the Core CLR section in the project.json file as shown below in the screen shot.

As soon as i commented the above section, below references got refreshed automatically.

Now, when i build the app then it will build fine. But, suppose you want the other way means you would like to keep the cloud optimized version also and build should also succeed. For this scenario i need to refer the conditional build as shown below.

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Today I will explain about how to use entity framework 7 to presist movie data to a database. But before you start, you must add Entity Framework 7 NuGet packages to your project. Also make sure that your project.json file includes the following two dependencies (you’ll get Intellisense while entering the names of the packages and their versions).

"EntityFramework.SqlServer": "7.0.0-beta2",
"EntityFramework.Commands": "7.0.0-beta2",

After you complete this step, the Entity Framework packages should appear under References.

Creating the Model and DbContext

Next, we need to create our Movie model class. This class represents the entity that we want to store in the database. Add the following Movie.cs class to your Models folder:

namespace MovieAngularJSApp.Models
{
    public class Movie
    {
        public int Id { get; set; }
 
        public string Title { get; set; }
 
        public string Director { get; set; }
    }
}

We also need to create an Entity Framework DbContext class. We create this class when using Entity Framework 7 in exactly the same way as we created this class for previous versions of the Entity Framework.

using Microsoft.Data.Entity;
namespace MovieAngularJSApp.Models
{
    public class MoviesAppContext:DbContext
    {
 
        public DbSet<Movie> Movies { get; set; }
 
    }
}

Registering the Entity Framework Services
Now that we have our DbContext class, we need to register the DbContext with our application services. Modify your Startup.cs file so it contains the code for registering the Entity Framework in the code below:

using Microsoft.AspNet.Builder;
using Microsoft.Framework.DependencyInjection;
using Microsoft.Data.Entity;
using MovieAngularJSApp.Models;
using Microsoft.AspNet.Hosting;
using Microsoft.Framework.ConfigurationModel;
namespace MovieAngularJSApp
{
    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            // Setup configuration sources.
            Configuration = new Configuration()
                .AddJsonFile("config.json")
                .AddEnvironmentVariables();
        }
         public IConfiguration Configuration { get; set; }
         public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
 
            // Register Entity Framework
            services.AddEntityFramework(Configuration)
                .AddSqlServer()
                .AddDbContext<MoviesAppContext>();
        }
        public void Configure(IApplicationBuilder app)
        {
            app.UseMvc();
        }
 
    }
}

The database connection string is loaded up from the Config.json file (notice the constructor in the Startup.cs file). Here is what the Config.json file looks like:

{
    "Data": {
        "DefaultConnection": {
            "ConnectionString": "Server=(localdb)\\mssqllocaldb;Database=MoviesDatabase;Trusted_Connection=True;MultipleActiveResultSets=true"
        }
    },
    "EntityFramework": {
        "MoviesAppContext": {
            "ConnectionStringKey": "Data:DefaultConnection:ConnectionString"
        }
    }
}

Updating the MoviesController

Because we registered our MoviesAppContext class as a service, we can take advantage of the built-in ASP.NET 5 Dependency Injection framework to use the MoviesAppContext in our MoviesController. Notice that the MoviesAppContext class is added to the MoviesController using constructor dependency injection in the code below:

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNet.Mvc;
using MovieAngularJSApp.Models;
namespace MovieAngularJSApp.API.Controllers
{
    [Route("api/[controller]")]
    public class MoviesController : Controller
    {
        private readonly MoviesAppContext _dbContext;
 
        public MoviesController(MoviesAppContext dbContext)
        {
            _dbContext = dbContext;
        }
 
        [HttpGet]
        public IEnumerable<Movie> Get()
        {
            return _dbContext.Movies;
        }
        [HttpGet("{id:int}")]
        public IActionResult Get(int id)
        {
            var movie = _dbContext.Movies.FirstOrDefault(m => m.Id == id);
            if (movie == null) {
                return new HttpNotFoundResult();
            } else {
                return new ObjectResult(movie);
            }
        }
        [HttpPost]
        public IActionResult Post([FromBody]Movie movie)
        {
            if (movie.Id == 0)
            {
                _dbContext.Movies.Add(movie);
                _dbContext.SaveChanges();
                return new ObjectResult(movie);
            }
            else
            {
                var original = _dbContext.Movies.FirstOrDefault(m => m.Id == movie.Id);
                original.Title = movie.Title;
                original.Director = movie.Director;
                _dbContext.SaveChanges();
                return new ObjectResult(original);
            }
        }
        [HttpDelete("{id:int}")]
        public IActionResult Delete(int id)
        {
            var movie = _dbContext.Movies.FirstOrDefault(m => m.Id == id);
            _dbContext.Movies.Remove(movie);
            _dbContext.SaveChanges();
            return new HttpStatusCodeResult(200);
        }
 
 
    }
}

Performing Database Migrations

After we complete all of the steps above, our application still won’t work. If we run the Movies app then we will get an error message about not being able to open the MoviesDatabase.

The Entity Framework 7 does not support database initializers. Instead, you are encouraged to use Database Migrations.There are two ways to use Migrations with ASP.NET 5: from a Command Prompt or from the NuGet Package Manager Console. I used the Command Prompt approach and I executed the following two commands from the same directory that contains my project.json file:

k ef migration add initial
k ef migration apply

After you execute the two ef commands above, a new database named MoviesDatabase will be created. You can see the new database by opening up the Visual Studio SQL Server Object Explorer:

Executing the ef commands above will also add a new Migrations folder to your project.

You now should be able to run the Movies app successfully.

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Here's a really short and easy little bit of code that has the potential to be slightly of a time-saver. The FindControl method of the control class is used to find a specific child control of a given parent, searching by ID. This method, however, does not search the control hierarchy recursively: it searches the direct children of the specified parent control only. While writing a recursive version of this method is trivial, a rather nice way to make the technique reusable is to implement it as an extension method. Here's how it can be done:

//search the children
foreach (Control child in control.Controls)
{
    ctrl = FindControlRecursive(child, id);
    if (ctrl != null) break;
}
}

return ctrl;
}

}
}

And to call it:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using Boo.Web.UI.Extensions;

namespace MyWebApp
{
public partial class WebForm1 : System.Web.UI.Page

{
    public void Page_Load(object sender, EventArgs e)
    {
       //call the recursive FindControl method
        Control ctrl = this.FindControlRecursive("my_control_id");
    }
}
}

Now, don't forget to import the namespace within which the extensions method class is declared- or a compilation error will not long follow. Now, all you need to do is import this same namespace for any pages/user controls/custom controls which need to use the recursive control search and you're good to go.

Doing it this way is of course logically no different to creating a static method in a util class, and passing both the parent control and the ID of the child control you want to find to it, but considering how commonly this functionality is required, it's nice to be able to tack it onto the control class itself, and extension methods provide an elegant way to accomplish this.

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Hi, In this post let me explain you about how to verify if  the remote files exist or not in ASP.NET 5.  Sometimes we need to verify if a file exists remotely such as javascript or image file.  Suppose you are in server(xxx.com) and you want to check a file in another server(xxxxxx.com) - in this case it will be helpful. And now, write the following code snippet.

Using HTTPWebRequest:
private bool RemoteFileExistsUsingHTTP(string url)
{
try
{
 //Creating the HttpWebRequest
 HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
 //Setting the Request method HEAD, you can also use GET too.
  request.Method = "HEAD";

  //Getting the Web Response
  HttpWebResponse response = request.GetResponse() as HttpWebResponse;

  //Returns TURE if the Status code == 200
  return (response.StatusCode == HttpStatusCode.OK);
}
catch
{
//Any exception will returns false.
return false;
}
}

Using WebClient:
private bool RemoteFileExistsUsingClient(string url)
{
bool result = false;
using (WebClient client = new WebClient())
{
try
{
    Stream stream = client.OpenRead(url);
    if (stream != null)
    {
           result = true;
    }
    else
    {
           result = false;
    }
}
catch
{
 result = false;
}
}
return result;
}

Call Method:
RemoteFileExistsUsingHTTP("http://localhost:16868/JavaScript1.js");

Don't confuse here as a result of it absolutely was implemented in 2 ways. continually use HttpWebRequest class over WebClient because of the following reasons:
1. WebClient internally calls HttpWebRequest
2. HttpWebRequest has a lot of options (credential, method) as compared to Webclient

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In this post, I will explain you about how to create QR Code Generator with ASP.NET 5. Though there are several solutions for QR Code generation in ASP.NET 5, all of it needs referring to third party dlls. however there's a really simple alternative through that we can create a QR code generator in ASP.Net within minutes without relating any third party dlls. Let's produce a ASP.Net web application with a text box, image control and Button with the following code
<asp:TextBox runat="server" ID="txtData"></asp:TextBox> 
   <asp:Button runat="server" ID="btnClickMe" Text="Click Me" OnClick="btnClickMe_Click" /> 
<br /> 
<asp:Image runat="server" ID="ImgQrCode" Height="160" Width="160" /> 

Now, in the button click event, generate the URL for the API with the data entered in the text box and size of the image control and set it to the image control's image URL property. Write the following code:
protected void btnClickMe_Click(object sender, EventArgs e) 
{ 
   ImgQrCode.ImageUrl = "https://chart.googleapis.com/chart?   cht=qr&chl=" + WebUtility.HtmlEncode(txtData.Text) + "&choe=UTF-8&chs=" + ImgQrCode.Height.ToString().Replace("px", "") + "x" + ImgQrCode.Width.ToString().Replace("px", ""); 
} 

And here is the output:

I hope this tutorial works for you!

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In this example, I will tell you how to  Bind the empty Grid with Header and Footer when no data in GridView and binding the grid using XML data and performing CURD operations on XML file.

First create a new project one your Visual Basic Studio and then write the following code:
using System; 
using System.Collections.Generic; 
using System.Data; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Xml; 
namespace OvidMDSample  
{ 
public partial class Home: System.Web.UI.Page  
{ 
private const string xmlFilePath = "~/XML/HiddenPagesList.xml"; 
public string domainUrl = HttpContext.Current.Request.Url.Authority; 
protected void Page_Load(object sender, EventArgs e)  
{ 
if (!IsPostBack) 
{ 
    BindHiddenPages(); 
} 
} 
private void BindHiddenPages()  
{ 
DataSet ds = new DataSet(); 
ds.ReadXml(Server.MapPath(xmlFilePath)); 
if (ds != null && ds.HasChanges()) 
{ 
    grdHiddenPages.DataSource = ds; 
    grdHiddenPages.DataBind(); 
}  
else  
{ 
    DataTable dt = new DataTable(); 
    dt.Columns.Add("ID"); 
    dt.Columns.Add("PageName"); 
    dt.Columns.Add("Description"); 
    dt.Columns.Add("PageUrl"); 
    dt.Columns.Add("Address"); 
    dt.Rows.Add(0, string.Empty, string.Empty, string.Empty); 
    grdHiddenPages.DataSource = dt; 
    grdHiddenPages.DataBind(); 
    grdHiddenPages.Rows[0].Visible = false; 
    // grdHiddenPages.DataBind(); 
} 
} 
} 
} 

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We create some true or false questions so the user can provide their answer and on a button click the solution are going to be saved to a database. Open your Visual Studio and build an empty web site, provide a suitable name (RadioButtonList_demo). In solution explorer you get your empty web site, add a web form and SQL database as in the following

For web Form:
RadioButtonList_demo (your empty website) then right-click then choose Add New Item -> internet type. Name it RadioButtonList_demo.aspx.

For SQL Server database:
RadioButtonList_demo (your empty website) then right-click then choose Add New Item -> SQL Server database. (Add the database within the App_Data_folder.) In Server explorer, click on your database (Database.mdf) then choose Tables ->Add New Table. create the table like this:

This table is for saving the data of the radio button list, I mean in this table we will get the user's answer of true and false questions. Open your RadioButtonList_demo.aspx file from Solution Explorer and start the design of you're application. Here is the code:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> 
<!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></title> 
<style type="text/css"> 
.style1 
{ 
width: 211px; 
} 
.style2 
{ 
width: 224px; 
} 
.style3 
{ 
width: 224px; 
font-weight: bold; 
text-decoration: underline; 
} 
.style4 
{ 
width: 211px; 
font-weight: bold; 
text-decoration: underline; 
} 
</style> 
</head> 
<body> 
<form id="form1" runat="server"> 
<div> 

</div> 
<table style="width:100%;"> 
<tr> 
<td class="style4"> 
    </td> 
<td class="style3"> 
    Please Answer these Questions</td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
     </td> 
<td class="style2"> 
     </td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
    <asp:Label ID="Label7" runat="server"  
        Text="Is Earth is the only planet in the universe??"></asp:Label> 
</td> 
<td class="style2"> 
    <asp:RadioButtonList ID="RadioButtonList1" runat="server" DataTextField="ans"  
        DataValueField="ans"> 
        <asp:ListItem>True</asp:ListItem> 
        <asp:ListItem>False</asp:ListItem> 
    </asp:RadioButtonList> 
</td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
    <asp:Label ID="Label5" runat="server" Text="Is Moon is our Natural Satellite?"></asp:Label> 
</td> 
<td class="style2"> 
    <asp:RadioButtonList ID="RadioButtonList2" runat="server" DataTextField="ans1"  
        DataValueField="ans1"> 
        <asp:ListItem>True</asp:ListItem> 
        <asp:ListItem>False</asp:ListItem> 
    </asp:RadioButtonList> 
</td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
    <asp:Label ID="Label6" runat="server"  
        Text="Earth is having Rings like Saturn have ?"></asp:Label> 
</td> 
<td class="style2"> 
    <asp:RadioButtonList ID="RadioButtonList3" runat="server" DataTextField="ans2"  
        DataValueField="ans2"> 
        <asp:ListItem>True</asp:ListItem> 
        <asp:ListItem>False</asp:ListItem> 
    </asp:RadioButtonList> 
</td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
     </td> 
<td class="style2"> 
     </td> 
<td> 
     </td> 
</tr> 
<tr> 
<td class="style1"> 
     </td> 
<td class="style2"> 
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Submit your answer" /> 
</td> 
<td> 
    <asp:Label ID="lbmsg" runat="server"></asp:Label> 
</td> 
</tr> 
<tr> 
<td class="style1"> 
     </td> 
<td class="style2"> 
     </td> 
<td> 
     </td> 
</tr> 
</table> 
</form> 
</body> 
</html> 

And here is the output:

Finally open your RadioButtonList_demo.aspx.cs file to write the code, for making the list box like we assume. Here is the code:
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Data; 
using System.Data.SqlClient; 
public partial class _Default : System.Web.UI.Page 
{ 
protected void Page_Load(object sender, EventArgs e) 
{ 

} 
protected void Button1_Click(object sender, EventArgs e) 
{ 
SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"); 
SqlCommand cmd = new SqlCommand("insert into tbl_data (ans,ans1,ans2) values (@ans,@ans1,@ans2)", con); 
cmd.Parameters.AddWithValue("ans", RadioButtonList1.SelectedItem.Text); 
cmd.Parameters.AddWithValue("ans1", RadioButtonList2.SelectedItem.Text); 
cmd.Parameters.AddWithValue("ans2", RadioButtonList3.SelectedItem.Text); 

con.Open(); 
int i = cmd.ExecuteNonQuery(); 
con.Close(); 

if (i != 0) 
{ 
lbmsg.Text = "Your Answer Submitted Succesfully"; 
lbmsg.ForeColor = System.Drawing.Color.ForestGreen; 
} 
else 
{ 
lbmsg.Text = "Some Problem Occured"; 
lbmsg.ForeColor = System.Drawing.Color.Red;             

} 
} 
} 

Output:

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ASP.NET validation is incredibly helpful and permits developers to confirm data is correct before it gets sent to a data store. Validation can run either on the client side or on the server side and each have their advantages and disadvantages. MVC and Webforms handle validation slightly otherwise and i will not get into those differences during this article. Instead, i'd prefer to explain some best practices and suggestions for you once implementing ASP.NET validation.

Bind Validation To HTML elements
To implement validation, you initially add an HTML element to a page, then a validation element points to it HTML part. In MVC, you'd write one thing like this for a model field known as Name.

<div class="editor-field col-md-10"> 
    <div class="col-md-6"> 
        @Html.TextBoxFor(model => model.Name, new { @class = "form-control" }) 
    </div> 
    <div class="col-md-6"> 
        @Html.ValidationMessageFor(model => model.Name) 
    </div> 
</div> 

In Webforms, write the following code:
<asp:DropDownList ID="Name" runat="server" AutoPostBack="true" FriendlyName="Option:" 
AddBlankRowToList="false" DisplayBlankRowText="False" CausesValidation="true"> 
<asp:ListItem Text="Option 1" Value="1"></asp:ListItem> 
<asp:ListItem Selected="True" Text="Option 2" Value="2"></asp:ListItem>
</asp:DropDownList> 
<asp:CustomValidator ID="valCheck" ControlToValidate="Name" Display="Static" runat="server" ForeColor="red" 
ErrorMessage="Validation Error Message" SetFocusOnError="True" 
OnServerValidate="CheckForAccess" /> 

This ends up in HTML elements with attributes that may enable the client-side validation framework to execute.

Check For Validation Errors On Postback
Whereas validation ought to run on the client-side before the form is submitted to the server, it's still a good observe to see for errors on the server. There are variety of reasons for this, however the most reason should be that the client is an unknown quantity. There are completely different browsers, JavaScript will be disabled, developer tools enable people to change HTML and thus may result in unexpected data being denote. So, check your validation before you start process your type data on the server. And it's as simple as wrapping your server-side logic in a single code block.

MVC
[HttpPost] 
[ValidateAntiForgeryToken] 
public ActionResult Edit(ViewModel model) 
{ 
if (ModelState.IsValid()) 
{ 
    // your code to process the form 
}  
else 
{ 
    ModelState.AddModelError(String.Empty, "Meaningful Error message); 
    return View(model); 
} 
return RedirectToAction("Index"); 
} 

Webforms
protected void Page_Load(object sender, EventArgs e) 
{ 
if (IsPostback) 
{ 
    if (!IsValid) 
    { 
        // validation failed. Do something 
        return; 
    } 
     
    // do your form processing here because validation is valid 
}  
else  
{ 
    // non-postback 
} 
} 

Do one thing useful with your Validation Errors
If you discover that validation errors have gotten through to your server, you would like to capture them and show them to the user. a quick way that I even have found to try and do this is with a loop using the validator collection and look for errors. There are variety of things you will do like add the error messages to the Validation summary box at the top of your form, write to an audit log or build them seem in a dialog box.

foreach (IValidator aValidator in this.Validators) 
{ 
if (!aValidator.IsValid) 
{ 
    Response.Write("<br />" + aValidator.ErrorMessage); 
} 
} 

Validation is a critical part of form submission and should be used to it's full potential.

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Html 5 being the fore runner in the Web technology today has offered a lot of benefit and enhancements that will make life of a developer easier than even before. One of such enhancement belongs to the support of offline data storage inside browser cache.  The offline data storage enhances the UI Experience of the end user by providing rich api to read local storage. HTML 5 supports the features that was never present before and you needed to rely on those events only using 3rd party plugins. Say for instance, you have a requirement to continue using your web application even though there is no availability of Internet. In this tutorial, I will show you how easily you can detect whether the site is running in online or offline mode.

Step 1

First, let us add a code:

var addEvent = (function () {
  if (document.addEventListener) {
    return function (el, type, fn) {
      if (el && el.nodeName || el === window) {
        el.addEventListener(type, fn, false);
      } else if (el && el.length) {
        for (var i = 0; i < el.length; i++) {
          addEvent(el[i], type, fn);
        }
      }
    };
  } else {
    return function (el, type, fn) {
      if (el && el.nodeName || el === window) {
        el.attachEvent('on' + type, function () { return fn.call(el, window.event); });
      } else if (el && el.length) {
        for (var i = 0; i < el.length; i++) {
          addEvent(el[i], type, fn);
        }
      }
    };
  }
})();

You should already  know there are browser compatibility issues as most of the browser still lacks standardization. The document.addEventListener works in most of the browsers except IE. So to handle this, you have to bypass the availability the eventhandler.

Step 2

Now to invoke the event we call:

addEvent(window, 'online', online);
addEvent(window, 'offline', online);
online({ type: 'ready' });

So basically, here you trap the online and offline events of the Window object using either using attachEvent or addEventListener to show the online or offline status. Lets take a look on the event handler:

function online(event) {
document.getElementById('status').innerHTML = navigator.onLine ? 'online' : 'offline';
}

So in the code you can easily detect using the network status of the browser using navigat0r.onLine, such that when it returns true, that means client is online or else otherwise.

Here are the steps to sumarize:

1. Add event listener to window.online / offline events
2. Use navigator.onLine to detect whether the application is in online state.
3. Do adjust your logic according to that.

The code works in most of the modern browsers. Happy coding :)

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Graphs and charts are important tools for the analysis of data. In this tutorial, you will look at how to represent data in terms of a bar chart and pie chart. To make this possible, we need the latest rendition of Microsoft's Graphics Device Interface (GDI+).

Scenarios to draw bar and pie charts

In this bar and pie chart example, it will represent the data of a fictitious country having 4 towns; namely: Town A, Town B, Town C and Town D. Their population will be modeled in terms of graphs and charts. The figures are given below:

Town    Population
  A       1,000,000
  B        600,000
  C       2,500,000
  D        800,000

Then, the bar chart should be outputted like this:

And the pie chart should be outputted like below:

Useful classes

Below are some of the useful classes that will be used to achieve what you want:

The Bitmap class

In windows application, you would have output graphical contents to one of the windows. Whereas in ASP.NET, there are no window. Fortunately, there is a class that can act as the drawing surface and that is the Bitmap class.

As any drawing surface has a width and a height, so does the Bitmap object. So, when we will create a Bitmap object, we will pass in a width and a height as parameters in the constructors. Moreover, we have to specify “Pixel Format Argument” which means whether the pixel format should be 24-bits RGB color, 32-bits RGB color, GDI-colors etc. In short the following code will do the work.

Dim Image As New Bitmap(500, 300, PixelFormat.Format32bppRgb)

The Graphics Class

Once you have created the Bitmap object, you need to obtain a Graphics object that references that Bitmap object. The following code will do the job.

' Get the graphics context for the bitmap.
Dim g As Graphics = Graphics.FromImage(Image)

The x vs. y coordinates system is illustrated in the figure below:

The Drawer

Now that you have a surface to draw, as you may have guessed, you will need a pen or brush to draw. To create a pen, a few properties of the pen should be specified; like the color of the pen and the width of the pen..

' Create a pen for drawing
Dim redPen As New Pen(Color.Red, 10)
 
' Create a blue brush
Dim blueBrush As New SolidBrush(Color.Blue)

Useful methods for drawing

Now that we have a set of drawing tools at our disposal, the graphics class also has a set of interesting methods to simplify our work for drawing objects like: circles, rectangles, text and the list goes on.

For this tutorial, you will be using the following self explanatory methods:

• Clear ( ): Cleans the graphics object (Pretty much like cleaning the whiteboard)
• DrawString ( ): For outputting text
• FillPie ( ): Draw a pie slice (useful for pie chart)
• FillRectangle ( ): Draws a rectangle (useful for bar charts)
• DrawLine ( ): Draws a line 

The above methods may be overloaded, so we used the names only. It is left to you as an option to explore how the overloaded methods.

How to Code the Chart Generator functions

Step 1

First of all create 2 buttons and label them Barchart and Piechart as shown in the figure below:

Step 2

Next, we shall declare some variables for the Bitmap object, Graphics object, population values, town names and the color representing each town. The code is as follows:

'   Variables declaration
Private myImage As Bitmap
Private g As Graphics
Private p() As Integer = {1000000, 600000, 2500000, 80000}
Private towns() As String = {"A", "B", "C", "D"}

Private myBrushes(4) As Brush

Next, in our Page_Load event, we will call a function that will create objects from the Bitmap and Graphics classes. We should also create the brushes that will be used for drawing the charts. The code snippet below does the job:

' Create an in-memory bitmap where you will draw the image.
' The Bitmap is 300 pixels wide and 200 pixels high.
myImage = New Bitmap(500, 300, PixelFormat.Format32bppRgb)
 
' Get the graphics context for the bitmap.
g = Graphics.FromImage(myImage)
 
'   Create the brushes for drawing
myBrushes(0) = New SolidBrush(Color.Red)
myBrushes(1) = New SolidBrush(Color.Blue)
myBrushes(2) = New SolidBrush(Color.Yellow)

myBrushes(3) = New SolidBrush(Color.Green)

Step 3

The bar charts have to be placed in a manner that we could draw the axes and label them as well. So, we declare an interval variable that will space the bar charts.

'   Variables declaration
Dim i As Integer
Dim xInterval As Integer = 100
Dim width As Integer = 90
Dim height As Integer
Dim blackBrush As New SolidBrush(Color.Black)
 
For i = 0 To p.Length - 1
    height = (p(i) \ 10000) '   divide by 10000 to adjust barchart to height of Bitmap
 
    '   Draws the bar chart using specific colours
    g.FillRectangle(myBrushes(i), xInterval * i + 50, 280 - height, width, height)
 
    '   label the barcharts
    g.DrawString(towns(i), New Font("Verdana", 12, FontStyle.Bold), Brushes.Black, xInterval * i + 50 + (width / 3), 280 - height - 25)
 
    '   Draw the scale
    g.DrawString(height, New Font("Verdana", 8, FontStyle.Bold), Brushes.Black, 0, 280 - height)
 
    '   Draw the axes
    g.DrawLine(Pens.Brown, 40, 10, 40, 290)         '   y-axis
    g.DrawLine(Pens.Brown, 20, 280, 490, 280)       '   x-axis
Next

The above code has only to be linked with the Click event of the “Barchart” button that was placed ok the page before. We have to keep track of the total angle so far and add the current angle produced by population[i] and use the FillPie method to draw the piechart.

Step 4

Next, to draw the pie chart, we make use of the following code:

'   Variables declaration
Dim i As Integer
Dim total As Integer
Dim percentage As Double
Dim angleSoFar As Double = 0.0
 
'   Caculates the total
For i = 0 To p.Length - 1
    total += p(i)
Next
 
'   Draws the pie chart
For i = 0 To p.Length - 1
    percentage = p(i) / total * 360
 
    g.FillPie(myBrushes(i), 25, 25, 250, 250, CInt(angleSoFar), CInt(percentage))
 
    angleSoFar += percentage
 
    '   Draws the lengend
    g.FillRectangle(myBrushes(i), 350, 25 + (i * 50), 25, 25)
 
    '   Label the towns
    g.DrawString("Town " & towns(i), New Font("Verdana", 8, FontStyle.Bold), Brushes.Brown, 390, 25 + (i * 50) + 10)
Next

The above code has to be linked with the Piechart Button's Click event.

Step 5

Now that we have the methods required to draw the charts, we should now output them on the browser. The piece of code below simply outputs the chart:

' Render the image to the HTML output stream.
myImage.Save(Response.OutputStream, _
System.Drawing.Imaging.ImageFormat.Jpeg)

Remember that myImage is the Bitmap object that we created earlier. Now, you can play around with the set of methods to produce other drawings or to improve the classes. You can also explore the rich set of methods and classes that the .NET framework provides you for producing drawings.

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