Saturday 8 April 2017

Angular 1 vs Angular 2

First thing, Angular 2 is not the upgrade of Angular 1 Angular 2 is completely rewritten.
Angular is using Typescript which is super set of javascript (It doesn’t mean only typescript, dart also).
Angular 1.x was not built with mobile support in mind, where Angular 2 is mobile oriented.
Angular 1 core concept was $scope, and you will not find $scope in angular 2.0. Angular 2 is using zone.js to detect changes. See the below code.
Angular 1.x controllers are gon. We can say that controllers are replaced with “Components” in Angular 2.

In Angular 2, Structural directives syntax is changed. ng-repeat is replaced with *ngFor.

In Angular 2, local variables are defined using hash(#) prefix.

Two-way data binding: ng-model replaced with [(ngModel)]

In Short below are the comparison points

· Angular 2 is mobile oriented & better in performance.

· Angular 2 provides more choice for languages.

· Angular 2 implements web standards like components.

· AngularJS 2.0 is not easy to setup as AngularJS 1.x.

· Angular 1.x controllers and $scope are gone.

· Different ways to define local variables.

· Structural directives syntax is changed.

· Angular 2 uses camelCase syntax for built-in directives.

· Angular 2, directly uses the valid HTML DOM element properties and events.

· One-way data binding directive replaced with [property].

· Two-way data binding: ng-model replaced with [(ngModel)]

· Way of Bootstrapping Angular Application is changed:

· Ways of Dependency Injection is Changed- syntax changed.

· Way of routing is Changed- syntax changed.

Saturday 10 December 2016

Exception Handling

Exception Handling (try- catch- finally)

What happens if a finally block throws an exception?

Three things will be happen

ONE # That exception propagates out and up, and it should be handled at a higher level. If it is not handled at the higher level, the application crashes.

TWO # The "finally" block execution stops at the point where the exception thrown.

Three #

a) if the "finally" block is being executed after an exception has occurred in the try block,

b)and if that exception is not handled

c) and if the finally block throws an exception

Then the original exception occurs in the try block is lost.

Will finally run if i put return in catch block?

Yes.The finally section is guaranteed to execute whatever happens including exceptions or return statement.

Does finally get executed if the code throws an error ?

Finally is always executed.

Is it mandatory for a piece of code to have catch or finally when try block is there ?

Yes. If a try block is there then either catch or finally has to be there or else a compiler error is generated.

Can finally bock have return statement ?

No,a compile time error is generated. Thats bcz finally contains the clean up code.

Can there be many catch statements for a single try block ?

Yes.But the rule is most specific exceptions should be caught first.

Will the foll code compile ?

           try
            {
                throw new SystemException();
            }
            catch(Exception e)
            {
            }
            catch(ArgumentException e)
            {
            }
No.It gives the foll error
A previous catch clause already catches all exceptions of this or of a super type ('System.Exception')

Thank you for taking your valuable time look at my blog - Sadiq Ali Syed

Friday 9 December 2016

Sealed Class

Sealed Class

Sealed classes are used to restrict the inheritance feature of object oriented programming. Once a class is defined as a sealed class, the class cannot be inherited.

In C#, the sealed modifier is used to define a class as sealed. If a class is derived from a sealed class then the compiler throws an error.
If you have ever noticed, structs are sealed. You cannot derive a class from a struct.
The following class definition defines a sealed class in C#:

// Sealed class

sealed class SealedClass

{

}

In the following code, I create a sealed class SealedClass and use it from Class1. If you run this code then it will work fine. But if you try to derive a class from the SealedClass, you will get an error.

using System;

class Class1

{

}

// Sealed class

sealed class SealedClass

{

}

Sealed Methods and Properties

You can also use the sealed modifier on a method or a property that overrides a virtual method or property in a base class. This enables you to allow classes to derive from your class and prevent other developers that are using your classes from overriding specific virtual methods and properties.

class X
{
  protected virtual void F() { Console.WriteLine("X.F"); }
  protected virtual void F2() { Console.WriteLine("X.F2"); }
}

class Y : X
{
  sealed protected override void F() { Console.WriteLine("Y.F"); }
protected override void F2() { Console.WriteLine("X.F3"); }
}

class Z : Y
{
  // Attempting to override F causes compiler error CS0239. 
  // protected override void F() { Console.WriteLine("C.F"); }
// Overriding F2 is allowed. 
  protected override void F2() { Console.WriteLine("Z.F2"); }
}

Why Sealed Classes?

We just saw how to create and use a sealed class. The main purpose of a sealed class is to take away the inheritance feature from the user so they cannot derive a class from a sealed class. One of the best usage of sealed classes is when you have a class with static members. For example, the "Pens" and "Brushes" classes of the "System.Drawing" namespace.

The Pens class represents the pens for standard colors. This class has only static members. For example, "Pens.Blue" represents a pen with the blue color. Similarly, the "Brushes" class represents standard brushes. "Brushes.Blue" represents a brush with blue color.

So when you're designing your application, you may keep in mind that you have sealed classes to seal the user's boundaries.

Thank you for taking your time to look at my blog- Sadiq Ali Syed.

Using

USING BLOCK

Generally in our applications we will write code like create connection object to handle connectionstring after that open a connection and create command object etc. to interact with database to get data that would be like this

It’s very easy way to write above code but problem is SqlConnection and SqlCommand objects will create IDISPOSABLE interface that means it could create unmanaged resources in our application to cleanup those objects we need to call Dispose() method at the end of our process otherwise those objects will remain in our application.

Suppose we use using statement in our applications it will automatically create try / finally blocks for the objects and automatically runs Dispose() method for us no need to create any try/finally block and no need to run any Dispose() method.

If we use using statement we need to write code will be like this

C# Code

In above code using statement no need to worry about close connection because using statement automatically close the connection once process is complete and automatically it will run Dispose() method to dispose objects.

The above using statement code will equal to below code

Thank you for taking your valuable time look at my blog - Sadiq Ali Syed

Wednesday 7 December 2016

Named Vs Optional Parameters

Optional Parameters

In C# 4.0 Parameters could be either required or optional. Now as a functional call, only required parameter is needed to pass. Optional Parameter, if not passed will take default value.

Syntax

Key Points about Optional Parameter:

Each Optional Parameter has a default value as its part of the definition.
If no argument is sent for the Optional Parameter default is being used.
Default value of the Optional Parameter must be constant

Optional Parameter must define at the end of the any required parameter.

Optional Parameter could be applied on Constructor, Method, and Indexer etc.

Named Parameters

One case where optional parameters run into trouble is when there is more than one optional parameter with the same data type. For example:

public void DoSomething(int a = 5, int b = 10){
...
}

In this case, it's not clear what a call to DoSomething(37) means. Are you passing in a or b? This is where named arguments come in handy. Named parameters (also new to .NET 4.0) allow you to specify which parameter you intended.

// a = 37.  b = the default value.

DoSomething(a: 37);

// a = the default value.  b = 37.

DoSomething(b: 37);

Syed Sadiq Ali

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Saturday 8 April 2017

Angular 1 vs Angular 2

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In Short below are the comparison points

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