Basic MVC

The Model

Models are the main component of your app, which is usually; what is stored and retrieve from the database, in our app, it will the tweet info and text.

The View

Views are the date in formatted form, delivered to the user. Here it will be the HTML pages.

The Controller

Controllers are the components that respond to all user requests, decide the appropriate response; which might be render a view, redirect to other URI or many other things.

Pros and Cons

• Pros

It has many pros, but these are the most remarkable:

1. Full control over the HTML, CSS, and JavaScript code, helping you to write clean, standards-compliant markup
2. It's Extensible which means that you can use a default component, or reconfigure it, or even use another component
3. HTTP friendly, it gives you total control over the requests passing between browser and server
4. Testability of MVC makes it simple to unit test the logic that is specific to a page, by testing controller methods

• Cons

It does not really have many cons compared to its pros:

1. The lake of drag and drop component in WebForms, despite that JQuery and other JavaScipt library overcome this problem
2. It's not as easy as WebForms, you should understand the role of each component individually and all of them together.

Configuring Multiple End points for WCF Service

Sample Service with multiple End Points

Step 1

Create a WCF Service Application. Open Visual studio and create new project selecting WCF Service Application project template. In VS2008, you will get WCF Service Application project template inside WEB tab whereas in VS2010, you will get WCF Service Application project template inside WCF tab.

Step 2

Delete the default code getting created for you by WCF. Delete all the code from IService1 and Service1. If you are using VS2008, comment out whole System.ServiceModel from Web.Config file. And if you are using VS2010 then comment out Multiple Host Binding.

Step 3

Generics classes Overview in C#.Net

Generics main benefit is eliminating boxing and unboxing that is true, there are also other benefits like type safety, by using generics you eliminate type ambiguitiy.

1. Generics provide type safety without the overhead of multiple implementations. Ex. We can create a linked list of string. LinkedListlinkList=new LinkedList(); There is no need to inherit from a base type and override members.The linked list is ready for immediate use.
2. There is no need to write code to test for the correct data type because it is enforced at compile time. The need for type casting and the possibility of run-time errors are reduced.
3. Generic collection types generally perform better for storing and manipulating value types because there is no need to box the value types
4. Generic delegates enable type-safe callbacks without the need to create multiple delegate classes.  

C# KeyNotFoundException

A KeyNotFoundException was thrown. This is likely caused by an invalid usage of the Dictionary collection. As always we want a quick way to fix the problem.

Example

First, here we see some code that looks correct, but actually has a severe flaw. The problem is that you cannot look up a key that doesn't exist in the Dictionary and try to assign your variable to its value.

The KeyNotFoundException here is thrown on the final line of try-block. The string "test" doesn't exist in the collection.

Program that throws KeyNotFoundException [C#]

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
    try
    {
        //
        // Create new Dictionary with string key of "one"
        //
        Dictionary<string, string> test = new Dictionary<string, string>();
        test.Add("one", "value");

        //
        // Try to access key of "two"
        //
        string value = test["two"];
    }
    catch (Exception ex)
    {
        //
        // An exception will be thrown.
        //
        Console.WriteLine(ex);
    }
    }
}

Output

System.Collections.Generic.KeyNotFoundException:
    The given key was not present in the dictionary.
at System.ThrowHelper.ThrowKeyNotFoundException()

Fix

Here we look at how you can fix this exception by using the TryGetValue method on the Dictionary constructed type. Note that could use ContainsKey instead of TryGetValue, but the below code preserves the intention of the previous code.

Program that does not throw [C#]

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
    Dictionary<string, string> test = new Dictionary<string, string>();
    test.Add("one", "value");
    //
    // Use TryGetValue to avoid KeyNotFoundException.
    //
    string value;
    if (test.TryGetValue("two", out value))
    {
        Console.WriteLine("Found");
    }
    else
    {
        Console.WriteLine("Not found");
    }
    }
}

Output

Not found

You always have to use the if statement when testing values in the Dictionary, because there is always a possibility that the key won't exist.

We saw how to raise and catch the KeyNotFoundException during runtime. We then saw how to avoid causing the exception. We discussed alternatives, such as TryGetValue and ContainsKey, and looked at a program that does not have this problem.

ASHX handler in Asp.Net

An ASHX handler allows you a discrete http handler without the overhead of processing a page request (an ASPX file).

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;

public class Handler : IHttpHandler {
   
    public void ProcessRequest (HttpContext context) {
        var fileName = "must.sql";
        var r = context.Response;
        r.AddHeader("Content-Disposition", "attachment; filename=" + fileName);
        r.ContentType = "text/plain";
        r.WriteFile(context.Server.MapPath(fileName));

    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }

}

 Now, You have to create button in your .aspx page write the code as following

<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />

protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Redirect("Handler.ashx");
    }

 

Stop default Auto-Complete of ASP.net TextBox on all browser

If you use textBox properties AutoCompleteType="Disabled" it disables the autocompletes of textBox on only Internet explorer. There's another way to stop auto-complete on all browsers. Use autocomplete="off" on from tag instead of AutoCompleteType = "Disabled". Again you can use the TextBox1.Attributes.Add("autocomplete", "off"); to stop auto-complete on only specific TextBox control.

So, my findings are use the following code to stop autocomplete on specific control

Activity logging and Error logging in ASP.NET

There are lots of error logging providers available such as log4Net, AnLogger, etc. they are easy to use as well, but just to keep it simple, I have written my own. I call it "Activity and Error Logger", it stores the data in XML format, request by request and session by session, you can actually create the user behaviour maps if you properly call the activity log at while performing any major operations. It also takes care of the concurrency, two threads will not overwrite each other. It logs the errors on page in try catch block and also at global level, in Application_Error event in global.asax.

RAISERROR statement in SQL server

RAISERROR statement is used to return error messages to the business applications that executes SQL statements. The usual errors returned by the SQL server may not make much sense to the business applications users hence we overwrite it by using RAISERROR to display meaningful messages. The statement uses same format as a system error or warning messages generated by SQL server.

You can return a user-defined error message by using RAISERROR.  The general syntax is as below

Spell as you Type plug-in

Full clientside spell checker for IE 6.0+ users that underlines misspellt words as you type into a textbox or textarea. Right click to see a list of suggested corrections.

Browsers such as Firefox and Chrome have spell as you type built in, this plugin will not have any effect in other browsers.

Use the dictionary supplied or create you own (plain text file, one word per line) using the dictionary builder application. The dictionaries supplied are over 500k each, so enable caching (and compression if available) on the server.

User Control Example

In this example I show that how easily we can create User Control and then use it in asp.net. Here first I create a User Control name CalendarUserControl.ascx, then place it Default.aspx web form. Here is the source code of both files.

Creating a UserControl

we will be building a UserControl for displaying information about a community user.
First of all, let's add a UserControl to our project. In your Visual Studio or Visual Web Developer, you should be able to right click on your project and select Add new item.. A dialog will pop up, and you should select the Web User Control from the list of possible things to add. Let's call our UserControl UserInfoBoxControl, with the filename of UserInfoBoxControl.ascx. Make sure that you have checked the checkbox which places code in a separate file, the so-called CodeBehind file.

You should now have a UserInfoBoxControl.ascx and a UserInfoBoxControl.ascx.cs in your project. The first is where we put our markup, and the second is our CodeBehind file. Now, if UserInfoBoxControl.ascx is not already open and selected, do so now. You will see only one line of code, the UserControl declaration. As mentioned, this control will be displaying information about a user, so let's get started adding some markup to do so:

ASP.net Ajax

ASP.net Ajax is Microsoft's free framework for creating Ajax (Asynchronous Javascript and XML) web applications. At its simplest, it lets ASP developers do this - or add Ajax controls to their existing applications - without leaving their familiar drag-and-drop environment, and without having to understand Javascript or asynchronous communication with the host. According to the O'Reilly Network, it protects developers from "the underlying gibberish that makes it [Ajax] all work".

View State Rendering

The problem in earlier versions is that the viewstate is rendered at the bottom of the page.
If the page is posted back before the entire page is loaded, the viewstate that is being submitted back to the server is incomplete and thus invalid.

This was fixed with .NET 3.5 SP1.

But You can Fix it by below Render function in earlier version of .NET