Assume how the Facebook application will store the millions of customer's record in real-time:

facebook = {
'jose': {
'name': 'jose', 'age': 33,
'hobby': ['cricket', 'python'], # cricket,football
'mobile': 1111111111, 'email': 'joset@gmail.com',
'contacts':[6666666666,3333333333,4444444444],
'pages': {
'python': {'sudha', 'priyanka'},
'BusinessMantra': {'sudha', 'oviya'}
}
},
'sudha': {
'name': 'sudha', 'age': 32, 'hobby': ['Khabadi', 'Movies', chess'],
'mobile': 2222222222, 'email': 'sudha.ram@gmail.com',
'contacts':[5555555555],
'pages':{
'python':{'sudha', 'lok'},
'furnitures': {'chris', 'priyanka'}
}
},
'lok': {
'name': 'lok', 'age': 26, 'hobby': ['python','football'],
'mobile': 3333333333, 'email': 'lok123@gmail.com',
'contacts':[3333333333,7777777777],
'pages':{
'python':{'chris', 'priyanka', 'jose'}
}
},
'priyanka': {
'name': 'priyanka', 'age': 26, 'hobby': 'football',
'mobile': 4444444444, 'email': 'pravi@gmail.com',
'contacts':[5555555555,3333333333,4444444444],
'pages':{'python':{'chris', 'jose'}}
},
'chris': {
'name': 'chris', 'age': 35, 'hobby': 'football',
'mobile': 5555555555, 'email': 'christopher.e@gmail.com',
'contacts':[6666666666,3333333333,4444444444]}
}

Assignment I(Store data):

1. You have to allow fb-customer to enter multiple hobbies with comma separator(,) and you have to store them as a list in db.
   Ex: 'jose': {'name': 'jose', 'age': '33', 'hobby': ['cricket', 'python']
2. Sync Contacts: Basically facebook(Messenger) will sync all your contacts to it's database. Here, the user will enter all his contacts(mobile numbers) with comma separator, that you have to store as a list like below,
   input: '6666666666,3333333333,4444444444' and store it in db like the below,
   'contacts':[6666666666,3333333333,4444444444]
3. Validate the input of mobile number as 10-digit(Ex:9876543210), ask repeatedly if they enter invalid input.
   Ex: Enter you mobile number:88 (if the user entered non 10-digit number, ask them correct mobile number until the valid input)
   Enter valid mobile number: 9876543210
4. Validate the Email-id with the format of Gmail account
5. Get the Age and Mobile number as integer input
6. A customer can run any number of pages, add an item as the above sample into their database with the pages and it's followers(set datatype)

Assignment II(Read operation):

1. Find the person who has the hobby same as I am looking: List all the customer who has cricket as hobby
2. Find the Target group for digital advt: A customer approaching FB to promote his page. How will they find the intended audience for the page-suggestion?
   Ex: I wants to promote my 'Python Development&Automation' page, then how will you pick the right person for my page among the millions of user-profile exist in the fb db.
3. Suggest Friend: We usually get friend suggestion from facebook analytics. Have you ever wonder how does it work..? Let's simulate this.
   As you know the pattern of stored data(facebook), you can classify the category like(same School/Company/Community/Birthplace/CurrentLocation/Contacts)
4. When the customer posting a status on their page, we have to let this know to all the followers
   Ex: sudha wants to post the status in his ‘furnitures’ page, notify this to all it's followers

- Basically , a Method is a piece of code used for the re-usability purpose. 

- Method is of 2 types Function and Procedure

- Function is a method which returns a value to the calling place

Procedure is a method which returns nothing to the calling place.

Procedure syntax:

<procedurename>(<params>[optional])

{

    //code

}

Procedure samples:

Display()

{

     Console.WriteLine("Procedure returns no value");

}

Add(int a, int b)

{

     Console.WriteLine("Sum : "+(a+b));

}

Hence, a function always returns a value or void to the calling place and a procedure returns nothing.

C# do not support Procedure. So functions in C# should be defined with the return type.

Control to validate an error message. Are common feature in all the controls.

Various validators are requiredfeild validator ,compare validator ,regular expression validator,custom validator,range validator  and validation summary.

1. Required field validator asks for the missing field in server side controls like textboxes dropdowlistot list box or checkboxlist and tells to populate in the form of error message.

2. Compare validator asks for two textboxes or familiar controls to have the exact match of the data types ore expressions.

3. Regular expression validator asks for correct format of email passwords and phone numbers or website address.

4. The custom validator does the same what regular expression validator does additionally it can customize its own features of validation by language coding means.

5.Validation summary. Display list of error messages in the form of bullet list on the top of the registration page etc.

6. Range validator checks whether the data types entered is falling in the correct ranges. Example values between two integer or dates or strings or float currencies etc..

• ArgumentException, ArgumentNullException, and ArgumentOutOfRangeException.
• NullReferenceException, IndexOutOfRangeException, SQL exceptions
• Stack Overflow Exception, Invalid Castexception

ArgumentException occurs due to the appearance of invalid argument types

argument null exception is due to null argument appearances. and out of range is when argument is defined which exceeds within its own bound levels.

null reference exception is when referencing an object you come across null character.

 IndexOutOfRangeException is when the index is defined beyond the actual bound levels. like in arrays. carrying integers of other characters.

sql exception is when mismatch happens between the number of rows or columns or irrelevant data types happens when client-side access the server side. in the database.

InvalidCastexception happens when the wrong type of casting happens between to data types for example between string and integer.

StackOverflowException happens when stacks try to acquire values beyond its own bound levels preassigned.

foreach is a looping statement :

• repeats a group of statements for each element in an array or an object collection. (or)
• used to iterate through the collection/ an array to get the required information.

Advantages:

• Easy implementation.
• Least possibility of errors. [ especially when working with index based values, like in arrays. ]

Syntax:

foreach(<datatype of collection / array> <variablename> <in> <collection/array>)
{

code....

}

Example:

foreach(string courseName in coursesList)
{

code....

}

• here, coursesList is a string collection
• string courseName is called as the "loop variable" which represents the element from the collection in each iteration.
• in is the pre-defined keyword

Working style of foreach loop:

• data type of loop variable must and should be the same as the data type of the array/collection that has to be referred.
• At the time of execution, first the foreach loop goes to the array/collection, counts the number of elements & repeats the loop that many times automatically.
• At each iteration array/collection location value will be copied into loop variable.

Example 1: In the below example, we'll see how to iterate a group of int type array elements using foreach loop.

Example 2: In the below example, we'll see how to iterate a group of values in a collection.

NOTE : in .NET we've different types of collections. For example we took "List" a generic collection

.NET development has started in the year 2000 , a product of Microsoft. From the begining of .NET development till now, it has got many RAD [ rapid application development ] facilities. 

Why .NET?

developed for distributed computing applications [ which access the data from any centralized locations ] , later due it's advantages and features started using for the development of desktop applications , web applications , mobile applications etc,.

What is .NET?

It's a framework which creates a "runtime environment" for .NET based applications.

Supports 61 programming languages like C# , Vb.net , F# etc,.

Components of .NET framework:

1. CLR [ common language runtime ] - which provides all the facilities and features to the .net application at the time of execution to execute the code. 
2. Assemblies / Base class libraries [BCL] - collection of types and resources that forms a logical unit of functionality. Also , known as building blocks for the .net applications and are self-describing in nature.