Notes on C# Programming

Access Modifiers in C#

In C#, access modifiers control the visibility of classes, methods, and other members:

• Public: Accessible by any code in the same or another assembly.
• Private: Accessible only within the same class or struct.
• Protected: Accessible within the same class, derived classes, or the same assembly.
• Internal: Accessible by any code in the same assembly.
• Protected internal: Accessible by code in the declaring assembly or derived classes in other assemblies.

Default Access Modifiers

In C#, classes are internal by default, while their members are private.

Interfaces in C#

Interfaces in C# can contain methods, properties, events, or indexers. Interface members are always public and cannot include access modifiers or be static.

Sealed Classes

A sealed class in C# cannot be inherited.

Constructor Behavior

If no constructor is explicitly defined, a default constructor is provided by the compiler.

Shadowing and Inheritance

When inheriting classes in C#, the new keyword can be used to indicate shadowing of inherited members.

Extension Methods

Extension methods allow adding new methods to existing types like integers using static classes and methods.

Named Arguments

In C#, named arguments can be used in method calls after positional arguments.

Indexers in C#

class IPAddress {
    public int[] ip;
    public int this[int index] {
        get { return ip[index]; }
        set { ip[index] = value; }
    }
}
IPAddress myIp = new IPAddress();
myIp[0] = 0;

Reference Variables and Generics

Reference variables use ref in both calling arguments and called parameters. They are commonly used in generics.

Conversion and Casting

C# provides various methods for conversions and casting, such as int.Parse for parsing integers and System.Convert.

Unmanaged Code

Unmanaged code in C# refers to code written outside the Common Language Runtime (CLR) and can be accessed using P/Invoke and COM Interop.

P/Invoke in C#

Static extern uint GetShortPathName([MarshalAs(UnmanagedType.LPStr)] string Pathname);

COM Interop

COM Interop in C# involves adding references, using dynamic data types, and utilizing interfaces for communicating with COM components.

Strings in C#

C# provides various constructors and methods for working with strings, including formatting options and immutable string behavior.

Delegates and Events

Delegates and events are powerful features in C# for implementing callbacks and event-driven programming.

Exception Handling

C# supports exception handling using try-catch blocks, custom exceptions, and serialization for cross-AppDomain exceptions.

Delegate in C# Programming

Introduction to Delegates

A delegate in C# is a type-safe function pointer that allows a method caller to connect dynamically to a target method. This feature enhances the flexibility and extensibility of C# code.

Key Points about Delegates:

• Delegates facilitate the writing of plug-in methods, enabling the dynamic invocation of methods at runtime, thus enhancing code flexibility and extensibility.
• Contravariance in delegates allows them to accept method parameters that are more derived than those of the target method, providing greater flexibility in method usage.
• Covariance enables a delegate’s return type to be more derived than the return type of its target method, allowing for a broader range of return types to be handled.
• C# provides built-in delegate types like Func and Action to simplify common scenarios where delegates are used.
• The System.Delegate class serves as the base for System.MulticastDelegate, which supports multiple methods within a single delegate instance and includes information about the target and method via the MethodInfo class.

Anonymous Delegates

An anonymous delegate in C# allows for the creation of a delegate without explicitly defining a named method. This is particularly useful for defining short, one-time method implementations inline.

delegate del = delegate(params) {};

Generics

Overview

Generics in C# allow for the creation of reusable classes, structures, methods, delegates, and interfaces with placeholder types.

Key Points

• Reusability: Generics provide reusability through a “template” that contains “placeholder” types.
• Covariance: Generic types are not covariant. This means that even if type B can be cast to type A, T<B> cannot be cast to T<A>.
• Constraints: There are three kinds of constraints in generics – derivation constraint, constructor constraint, and reference/value constraint.
• Derivation Constraint: In the derivation constraint, the base constrained type must never have lower visibility than the generic type parameter.
• Constraint Order: The order of constraints is important and should be followed as follows:
  1. Reference/Value Constraint
  2. Derivation Constraint
  3. Constructor Constraint

Example

            public class Example<T>
            {
                public T Value { get; set; }

                public Example(T value)
                {
                    Value = value;
                }
            }
        

Conclusion

Understanding generics in C# is crucial for creating flexible and reusable code. By leveraging generics, developers can write more efficient and maintainable code that can work with a variety of data types.

Understanding Indexers in C#

Indexers in C# provide a way to access elements in a class similar to arrays. They are defined using the this keyword, allowing objects of a class to be indexed like arrays. This feature enhances the flexibility and usability of classes in C#.

How Indexers Work

An indexer in C# is implemented using this keyword followed by square brackets containing the parameters that define the index. It can have one or more parameters based on the requirements. The get accessor is used to retrieve the value of an element at the specified index, while the set accessor is used to assign a value to the element at that index.

Here is a basic example of an indexer in C#:

public string this[int index]
{
    get { return someArray[index]; }
    set { someArray[index] = value; }
}

Benefits of Using Indexers

• Enhanced Readability: Indexers make the code more readable by providing a familiar syntax for accessing elements in a class.
• Custom Data Structures: Indexers allow for the creation of custom data structures that can be accessed using index notation.
• Convenience: Using indexers simplifies the process of accessing elements in a class, especially when dealing with collections or arrays.

Example of Indexer Implementation

Let’s consider an example where we create an indexer in a class to store and retrieve values based on a custom index:

public class CustomCollection
{
    private string[] data = new string[10];

    public string this[int index]
    {
        get { return data[index]; }
        set { data[index] = value; }
    }
}

Conclusion

Indexers in C# provide a powerful mechanism to access elements in a class in a way that resembles array indexing. By implementing indexers, developers can enhance the usability and functionality of their classes, making the code more intuitive and efficient.

Tags: C#, Programming World

The Power of LINQ in C# Programming

Introduction

LINQ (Language Integrated Query) is a powerful feature in C# that allows developers to write structured, type-safe queries over local object collections and remote data sources. It provides a more intuitive way to interact with data by using a set of query operators.

Key Concepts in LINQ

1. Sequences and Elements

In LINQ, sequences represent collections of data, while elements refer to individual items within those collections.

2. Query Operators

LINQ offers a wide range of query operators to manipulate data, including:
– Take, Skip, and Reverse for pagination.
– FirstOrDefault, LastOrDefault, SingleOrDefault, or ElementAtOrDefault for retrieving specific elements.
– Aggregation operators like Count, Min, Max, and Average for performing calculations.
– Contains, Any, All, and SequenceEquals for checking conditions.
– Concat, Union, Intersect, and Except for combining sets.

3. Lazy Evaluation

LINQ uses deferred or lazy evaluation, meaning that queries are not executed until the results are actually needed. However, lazy execution can be overridden by certain operators like element operators, aggregation operators, and conversion operators such as ToArray, ToList, ToDictionary, and ToLookup.

4. Chaining Query Operators

Developers can chain multiple query operators together to create complex queries that efficiently manipulate data.

5. Query Comprehension Syntax

LINQ supports query syntax or query comprehension syntax, which provides advantages such as:
– Ability to use let clauses to introduce new variables.
– Multiple generators (SelectMany) or Join/GroupJoin equivalents for complex queries.
– Proper scoping rules where variables declared in earlier parts of the query are accessible in subsequent parts.

6. Type Conversion

LINQ provides operators like Cast and OfType for type conversions, allowing developers to work with specific data types within their queries.

Conclusion

LINQ is a versatile tool in C# programming that simplifies data manipulation and querying. By leveraging LINQ’s query operators and syntax, developers can write efficient and expressive code to interact with various data sources seamlessly. Mastering LINQ can greatly enhance a developer’s productivity and the performance of their applications.

Understanding Interfaces in C# Programming

When working with C# programming, interfaces play a crucial role in defining the structure and behavior of classes. Here are some key points to keep in mind:

1. Implementing Multiple Interfaces

In C#, a class has the flexibility to implement multiple interfaces. This means that a class can inherit and define behaviors from multiple sources, enhancing its functionality and versatility.

2. Abstract Nature of Interfaces

Interfaces in C# are inherently abstract, meaning they provide a blueprint of methods and properties that must be implemented by any class that inherits them. This abstraction ensures consistency and standardization across different classes.

3. Contracts in Interfaces

An interface in C# can be viewed as a contract that defines a set of methods and properties that a class must implement. By adhering to this contract, classes ensure they provide specific functionalities, promoting code reusability and maintainability.

By understanding and effectively utilizing interfaces in C# programming, developers can create more structured, modular, and scalable codebases.

The Evolution of C# 4.0

C# 4.0 represented a significant advancement in the C# programming language, introducing new features that aimed to boost developer productivity and extend the language’s capabilities.

1. Dynamic Lookup with Dynamic Type

One of the standout additions in C# 4.0 was the introduction of the dynamic type. This feature allows for dynamic lookup of members during runtime, enabling developers to interact more seamlessly with dynamic languages and COM APIs. By postponing type checking until runtime, the dynamic type facilitates improved interoperability, particularly in scenarios where types are determined only at runtime.

2. Named and Optional Arguments

C# 4.0 introduced named and optional arguments to provide developers with enhanced flexibility when invoking methods. Named arguments allow parameters to be specified by name rather than by position, which contributes to better code readability and maintainability. On the other hand, optional arguments permit method parameters to have default values, reducing the necessity for numerous method overloads and simplifying method calls.

3. Variance in Generic Interfaces and Delegates

With C# 4.0, support for variance was extended to generic interfaces and delegates. This enhancement enables more flexibility in type assignments by allowing implicit conversions of generic types. By facilitating easier manipulation of collections and delegates, variance enhances code expressiveness and conciseness, streamlining the handling of generic types.

Understanding Boxing and Unboxing in C#

Boxing and Unboxing in C#

In C#, boxing is the process of converting a value type instance to an object reference type. It allows value types to be treated as objects, facilitating scenarios where value types need to be used as objects. On the other hand, unboxing is the reverse process of extracting the original value type from the object, requiring explicit type casting.

Boxing in C#

Boxing plays a crucial role when a value type needs to be stored in a data structure that expects objects, like collections. When a value type is boxed, it is wrapped inside an object allocated on the heap, enabling it to be manipulated as an object.

Unboxing in C#

Unboxing involves retrieving the original value type from the boxed object. This process requires explicit type casting to convert the object back to its original value type. Incorrect casting during unboxing can result in runtime errors, emphasizing the importance of accurate type conversions.

Key Points to Remember

• Boxing allows the conversion of a value type to a reference type, enabling value types to be treated as objects when necessary.
• Unboxing is the process of extracting the original value type from a boxed object by performing explicit type casting.
• Both boxing and unboxing incur performance overhead due to memory allocation and type conversions, so they should be used judiciously in C# programming.

Performance For Generics

Introduction

When working with generics in C#, it is essential to consider performance implications. The choice between using generics or objects can significantly impact the efficiency of your code.

Key Points to Consider:

• When we use object instead of a generic variable for value types, we incur overhead due to boxing. This inefficiency arises from the need to convert value types to objects, leading to performance degradation.
• Type safety during downcasting is crucial. Using generics ensures type safety, reducing the risk of runtime errors related to type mismatches.
• The server compiler compiles generics into Intermediate Language (IL), incorporating placeholders for types and associated metadata. This approach enables efficient handling of generic types during compilation.
• Client compilers convert IL to machine code, optimizing the performance for both value and reference types. This process involves replacing values directly and efficiently handling references by using objects where necessary. Emphasis is placed on code reuse rather than object reuse to enhance performance.
• Significant performance gains can be achieved by utilizing generics appropriately. Expect around a 200% performance improvement for value types and a 100% enhancement for reference types by leveraging generics effectively.

Conclusion

Understanding the performance implications of using generics in C# is crucial for developing efficient and optimized code. By prioritizing type safety and leveraging generics’ capabilities, developers can enhance the performance of their applications significantly.

Understanding Classes in C# Programming

Partial Classes and Methods

Partial classes in C# provide a way to split the definition of a class across multiple files. This feature is particularly useful in scenarios where a class becomes too large or when separating auto-generated code from custom code.

Automatic Properties

Automatic properties offer a convenient syntax for defining properties without explicitly specifying the backing field. They are commonly used for straightforward properties that do not require additional logic in their getter or setter methods.

Class Inheritance

• In C#, class inheritance allows a reference to a base class to point to an object of a subclass. This relationship enables code reusability and the implementation of polymorphism.
• Upcasting involves creating a reference to a base class from a subclass reference, while downcasting is the process of creating a subclass reference from a base class reference, requiring explicit casting.
• The as operator in C# performs a safe downcast, returning null if the downcast is not valid, while the is operator verifies the possibility of a successful downcast.

Abstract Classes and Virtual Members

An abstract class in C# serves as a template for other classes to inherit from but cannot be instantiated itself. Abstract members within such a class must be implemented by its subclasses, ensuring a consistent structure across derived classes.

By marking a method as virtual, it can be overridden by subclasses to provide specialized implementations, enabling polymorphic behavior in the program.

Constructor Behavior

When initializing objects in C#, constructors are executed in reverse order of declaration when transitioning from a subclass to a base class. This ensures that the initialization process occurs correctly within the class hierarchy.

Method Overloading

In C#, method overloading allows multiple methods within the same class to have the same name but with different parameters. During compilation, the most specific method based on the provided arguments is selected, promoting code flexibility and reusability.

Accessibility in Classes

• By default, classes in C# have internal accessibility if not nested within other classes. Internal classes are only accessible within the same assembly, promoting encapsulation and modular design.
• In C#, a subclass can have lower accessibility than its base class but not higher. This restriction ensures that the subclass does not expose more than what the base class intends to make available, maintaining the principle of least privilege.