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•structs are value types that can contain data and functions
•structs are value types and do not require heap allocation.
•structs directly store their data in the struct, classes store a reference to a dynamically allocated object.
•structs are useful for small data structures
•structs can affect performance
•Constructors are invoked with the new operator, but that does not allocate memory on the heap
•A struct constructor simply returns the struct value itself (typically in a temporary location on the stack), and this value is then copied as necessary
•With classes, multiple variables may have a reference to the same object
•It is possible for operations on one variable to affect the object referenced by the other variable.
•With structs, the variables each have their own copy of the data, and it is not possible for operations on one to affect the other.
•structs do not support user-specified inheritance, and they implicitly inherit from type object
#2: How would you count the occurrences of a string within a string?
•The string type is a sealed class type that inherits directly from object. Instances of the string class represent Unicode character strings.
•Values of the string type can be written as string literals.
•The keyword string is simply an alias for the predefined class System.String so you can use string name = “Fred”; or String name = “Fred”;
•Likewise you can use string.Concat() or String.Concat()
•Use string for variable names
•Use String for class methods and reference
#3: Encrypt/Decrypt a String in .NET
Use C# inbuilt Cryptography Class (DES,RSA etc)
#4: How do I Make a Texbox that Only Accepts Numbers?
Use NumericUp Down
Handel the KeyPress Event(Text.isDigit )
Handel the Text_Changed Event (Not recommended)
#5: How Does One Parse XML Files?
•Reference System.Xml
•Use XmlReader to parse the text string
•You will need to have an idea of the XML elements and attributes for this example
•Use the XmlReader methods to read the XML data
#6: How to Check if a Number is a Power of 2
Use Regex or foreach
#7: How do I Get the Index of the Current Iteration of a foreach Loop?
Maintain a counter and increment it manually
Some collection type provide IndexOf()
#8: How do I Round a Decimal Value to 2 Places for Output?
•Use string format specifiers
•(“#.##”)
•(“{0:0.00}”, value)
•(“n2”)
•(“{0:c}”, value)
#9: What is the Difference between String and string
•The string type is a sealed class type that inherits directly from object. Instances of the string class represent Unicode character strings.
•Values of the string type can be written as string literals.
•The keyword string is simply an alias for the predefined class System.String so you can use string name = “Fred”; or String name = “Fred”;
•Likewise you can use string.Concat() or String.Concat()
•Use string for variable names
•Use String for class methods and reference
#10: C# Loop — break vs continue
• Break will exit the loop completely, Continue will just skip the current iteration and then test the while statement again.
#11: How to Get My Own IP address in C#
check private IP address
Use Dns.GetHostEntry , IPAddress and AddressList
Ignore APIPA 16.254 starting address
Check public IP address- Make External calls
To Check Public IP address
#12: Remove Duplicates from an Array
•Use LINQ (Use DistinctElement )
•Use a List
#13: How do I get the Application’s Path in a C# Console App?
•Use reflection to get the executing assembly path
•Pass that the IO.Path.GetDirectoryName
#14: Difference Between abstract and virtual functions
Abstract Method have no implementation and MUST be overridden
Virtual methods MAY have an implementation but are not requireed to and they can be overridden
You cannot call base,method() for abstract but you can for virtual methods
ref causes an argument to be passed by reference not by value .It provides a reference to the source value and changes made in the method will be made by the source object
arguments passed as ref must be initialized before thy are passed
out alos cause the argument to be passed as reference. Changes made to the parameters are also changed in the source
Arguments passed out do not have to be initialized first
The called method must assign a value prior to the method return
#19: How do I get the String Value of an enum?
Use Enum.GetName()
USe ToString
#20: How Can I Return Multiple Values From a Function in C#?
Object orineted Programing ; Managed Language & C#
What is Object Oriented Programming
To be object oriented, a language is designed around the concept of objects. that are something, have certain properties and exhibit certain behaviors. This means the language generally includes support for: —
Encapsulation — Inheritance — Polymorphism
What is Managed Language
Managed languages depend on services provided by a runtime environment.
• C# is one of many languages that compile into managed code.
• Managed code is executed by the Common Language Runtime (CLR).
• The CLR provides features such as: — Automatic memory management — Exception Handling — Standard Types — Security
There are 3 categories of types:
— Value types : these directly store values
— Reference types:or objects, store a reference to data
— Pointer types:only available in unsafe code
What are Lambda Expressions
An enhancement of anonymous methods
• An unnamed method written inline
• An alternative to a delegate
• At compile time a lambda expression becomes either: — An instance of a delegate — Or an expression tree
• Expressions are validated at compile time, but evaluated at run time.
• Dynamic expression trees are supported
Module 2:
Constructing Complex Types, Object Interfaces and Inheritance and Generics
Classes and Structs
• A class or struct defines the template for an object.
A class represents a reference type
A struct represents a value type
Reference and value imply memory strategies
When to Use Structs :
Use structs if:
— instances of the type are small
— the struct is commonly embedded in another type
— the struct logically represent a single value
— the values don’t change (immutable)
— It is rarely “boxed” (see later)
• Note: structs can have performance benefits in computational intensive applications
Note : Useful : 2 classes inside same namespace
Inheritance
— Classes can optionally be declared as:
static — can never be instantiated
abstract — can never be instantiated; it is an incomplete class
sealed — all classes can be inherited unless marked as sealed
— Virtual Methods
Virtual methods have implementations
They can be overridden in derived class.
What are Virtual Functions
Virtual Function is a function in base class, which is overrided in the derived class, and which tells the compiler to perform Late Binding on this function.
Virtual Keyword is used to make a member function of the base class Virtual.
