Mastering c and NET framework deep dive into c and NET architecture to build efficient, powerful applications

Other tools and utilities can be installed from the Extensions and Updates menu option, linked to the Tools menu in the different versions of Visual Studio.. Context As Wikipedia states:

Mastering C# and NET

Mastering C# and NET Framework

Copyright © 2016 Packt Publishing

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Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals However, Packt Publishing cannot guarantee the accuracy of this information.First published: December 2016

About the Author

Marino Posadas is an independent senior trainer, writer, and consultant in

Microsoft Technologies and Web Standards He is a Microsoft MVP in C#, Visual Studio, and Development Technologies; an MCT, MAP (2013), MCPD, MCTS, MCAD, MCSD, and MCP Additionally, he was the former director for development

in Spain and Portugal for Solid Quality Mentors

He's published 14 books and more than 500 articles on development technologies in several magazines Topics covered in his books range from Clipper and Visual Basic 5.0/6.0 to C #, NET-safe programming, Silverlight 2.0 and 4.0, and Web Standards

The Guide to Programming in HTML5, CSS3 and JavaScript with Visual Studio is his

latest book

He is also a speaker at Microsoft events, having lectured in Spain, Portugal, England, the USA, Costa Rica, and Mexico

You can find him on LinkedIn at https://es.linkedin.com/in/mposadas

His website, http//elavefenix.net, also contains developer's resources and videos, in English and Spanish, interviewing representatives of the Microsoft and Web Standards development world

I'd like to thank Denim Pinto, Priyanka Mehta, and Fabio Claudio Ferracchiati from Packt Publishing for their continuous support and confidence while writing this book

Special thanks to some professionals and technology evangelists whose work

inspired different parts of this book, in particular, Mark Russinowich, Scott

Hanselman, Scott Hunter (the "lesser" Scotts), Daniel Roth, Lluis Franco, Luis Ruiz Pavón, Dino Esposito, Miguel Katrib, James Gray, Paul Cotton, Stephen Toub, and Troy Hunt

Also, I would like to remember my MVP lead, Cristina González Herrero, for her continuous encouragement and help, and other people at Microsoft who have always supported my activities My memories go here to Alfonso Rodríguez, David Carmona, David Salgado, José Bonnín, César de la Torre, Andy Gonzalez, and Leon Welicki

My appreciation also goes to my mates at Netmind, Alex and Bernat Palau, Miquel Rodriguez, Israel Zorrilla, and Angel Rayo, for their support in this initiative from the beginning

About the Reviewer

Fabio Claudio Ferracchiati is a senior consultant and a senior analyst/

developer using Microsoft technologies He works for React Consulting (www

reactconsulting.it) as Microsoft Dynamics 365 Solution Architect He is a

Microsoft Certified Solution Developer for NET, a Microsoft Certified Application Developer for NET, a Microsoft Certified Professional, and a prolific author

and technical reviewer Over the past 10 years, he's written articles for Italian

and international magazines and coauthored more than 10 books on a variety of computer topics

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with a special mention to my nephews and nieces: Fernando, Sarah, Ana, Paula, Pablo, Javier, Adrian, Irene, Luis, and Juan.

Table of Contents

Preface xi

Metadata 21

A quick tip on the execution and memory analysis of an assembly in

Relevant features appearing in versions 4.5x, 4.6, and

Chapter 2: Core Concepts of C# and NET 53

Generics 64

Chapter 3: Advanced Concepts of C# and NET 83

Tuples: implementation in C# 93

Tuples 122 Decomposition 124

Lists 137

A note on TypeScript's object-oriented syntax 155

Summary 156

Chapter 5: Reflection and Dynamic Programming 157

Interoperability 173

Summary 197

Chapter 6: SQL Database Programming 199

Summary 224

Chapter 7: NoSQL Database Programming 225

MongoDB on Windows 233

Deletion 248 Insertion 249

Summary 251

An entire open source sample for you to check: ScriptCS 265

TypeScript 277

Functions 285

Summary 295

Chapter 9: Architecture 297

Reports 324

BPMN 2.0 (Business Process Model and Notation) 326

Testing 332

Summary 338

Dependency Inversion principle 359

Singleton 365

Summary 379

Chapter 11: Security 381

Prevention 387

Prevention 408

A8 – Cross-Site Request Forgery 409

Prevention 410

Summary 445

.NET and the C# language have continuously grown in adoption since its release

in early 2001 C#'s main author, Anders Hejlsberg, has lead several groups of

developers in constant growing and improvement, until reaching the current

version, NET 4.6, and the very important NET Core 1.0/1.1, and keeps on going with this work, also linked to the new TypeScript language, which we will also cover

in this book

This book is a journey through the different options and possibilities NET

Framework in general, and C# in particular, provide to developers to build

applications that run on Windows and, as seen in the last chapter, on other platforms and devices

I believe that it can be a reference for programmers wanting to update their

knowledge to the latest versions of this set of technologies, but also for those who, coming from other environments, would like to approach NET and the C# language

to extend their skills and programming toolset

All the main points discussed in here are illustrated with examples, and the

important parts of these demos are explained in detail, so you can easily follow this route

What this book covers

Chapter 1, Inside the CLR, goes through the internal structure of NET, the way

assemblies are built, the tools and resources we have to work with them,

and the way NET integrates with the operating system

Chapter 2, Core Concepts of C# and NET, reviews the foundations of the language,

its main characteristics, and some of the true reasons for the appearance of certain features, such as delegates

Chapter 3, Advanced Concepts of C# and NET, starts with version 4.0, viewing some

common practices new to the language and Framework libraries, especially those related to synchronicity, execution threads, and dynamic programming Finally,

we can find many new aspects that appeared in versions 6.0 and 7.0, intended to simplify the way we write code

Chapter 4, Comparing Approaches for Programming, deals with two members of the

.NET language ecosystem: F# and TypeScript (also called functional languages), which are gaining momentum among the programmer's community

Chapter 5, Reflection and Dynamic Programming, covers the ability of a NET program

to examine, introspect, and modify its own structure and behavior, and also how

to interoperate with other programs, such as the Office Suite

Chapter 6, SQL Database Programming, deals with access to databases built according

to the principles of the Relational Model, and in particular to SQL databases It covers Entity Framework 6.0 and gives a brief reminder of ADO.NET

Chapter 7, NoSQL Database Programming, reviews the emerging database paradigm

called NoSQL databases We will use MongoDB, the most popular of its kind, and see how to manage it from C# code

Chapter 8, Open Source Programming, goes through the current state of open source

programming with Microsoft technologies, the open source ecosystem We will review Node.js, Roselyn, and also TypeScript, although with a slightly different point of view

Chapter 9, Architecture, goes through the structure of an application and the tools

available in its construction, such as MSF, good practices, and so on

Chapter 10, Design Patterns, focuses on the quality of the code and its structures in

terms of efficacy, precision, and maintainability It deals with SOLID principles, the Gang of Four patterns, and other proposals

Chapter 11, Security, analyzes the OWASP Top 10 security recommendations from

the point of view of the NET developer

Chapter 12, Performance, deals with common issues that a developer encounters

in relation to an application's performance, and which techniques and tips are commonly suggested in order to obtain flexible, responsive, and well-behaved software, with a special emphasis on web performance

Chapter 13, Advanced Topics, covers interaction with the OS via subclassing and

platform/invoke, system data retrieval through WMI, parallel programming, and an introduction to the new NET Core and ASP.NET Core multiplatform technologies

What you need for this book

As this book is dedicated to C# and NET, the main tool to use is Visual Studio However, you can use several versions to follow the majority of the sections in this book

I've used Visual Studio 2015 Ultimate Update 3, but you can also use the free

Community Edition for more than 90% of its contents Other available options are Visual Studio 2015 Express Edition, which is also free, and Visual Studio Code, which is also free and multiplatform

Additionally, a basic installation of SQL Server Express 2014, which is free, is

required together with the SQL Server Management Studio (version 2016 works equally well with the topics covered here)

For the NoSQL part, MongoDB is also required in its basic installation

To debug websites, it's good to have Chrome Canary or Firefox Developer Edition, for they have extended capabilities for developers

Other tools and utilities can be installed from the Extensions and Updates menu option, linked to the Tools menu in the different versions of Visual Studio.

Finally, in some cases, there are tools that you can download from the sites

indicated in this book; although, they're not an absolute requirement for the full comprehension of this book's contents

Who this book is for

This book was written exclusively for NET developers If you're creating C#

applications for your clients, at work or at home, this book will help you develop the skills you need to create modern, powerful, and efficient applications in C#

No knowledge of C# 6/7 or NET 4.6 is needed to follow along—all the latest features are included to help you start writing cross-platform applications immediately You will need to be familiar with Visual Studio, although all the new features in Visual Studio 2015 will also be covered

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information Here are some examples of these styles and an explanation of their meaning

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows:

"We use the ForEach method, which receives an Action delegate argument."

A block of code is set as follows:

static void GenerateStrings()

{

string initialString = "Initial Data-";

for (int i = 0; i < 5000; i++)

New terms and important words are shown in bold Words that you see on the

screen, for example, in menus or dialog boxes, appear in the text like this: "In the

Memory Usage tab, we can take a snapshot of what's going on."

Warnings or important notes appear in a box like this

Tips and tricks appear like this

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In short, this chapter covers the following topics:

• A brief, but carefully selected, dictionary of the common terms and concepts utilized in general and NET programming

• A rapid review of goals after the creation of NET and the main architects behind its construction

• Explanations of each of the main parts that compose the CLR, its tools, and how the tools work

• A basic approach to the complexity of algorithms and how to measure it

• A select list of the most outstanding characteristics related to the CLR that appeared in recent versions

An annotated reminder of some

important computing terms

Let's check out some important concepts widely used in software construction that show up frequently in NET programming

Context

As Wikipedia states:

In computer science, a task context is the minimal set of data used by a task (which may be a process or thread) that must be saved to allow a task interruption at a

given date, and a continuation of this task at the point it has been interrupted and

at an arbitrary future date.

In other words, context is a term related to the data handled by a thread Such data is conveniently stored and recovered by the system as required

Practical approaches to this concept include HTTP request/response and database scenarios in which the context plays a very important role

The OS multitask execution model

A CPU is able to manage multiple processes in a period of time As we mentioned, this is achieved by saving and restoring (in an extremely fast manner) the context of execution with a technique called context switch

When a thread ceases to execute, it is said to be in the Idle state This categorization

might be useful at the time of analyzing processes execution with the tools that are

able to isolate threads in the Idle state:

Process P0 Operating System Process P1

Executing Interrupt or system call

Save state into PCB0

Reload state from PCB1

Save state into PCB1

Reload state from PCB0

Context types

In some languages, such as C#, we also find the concept of safe or secure context In

a way, this relates to the so-called thread safety

Thread safety

A piece of code is said to be thread-safe if it only manipulates shared data structures

in a manner that guarantees safe execution by multiple threads at the same time There are various strategies used in order to create thread-safe data structures, and the NET framework is very careful about this concept and its implementations

Actually, most of the MSDN (the official documentation) includes the indication this

type is thread-safe at the bottom for those to whom it is applicable (a vast majority).

The state of a computer program is a technical term for all the stored information, at

a given instant in time, to which the program has access The output of a computer program at any time is completely determined by its current inputs and its state A very important variant of this concept is the program's state

In addition, a common taxonomy of programming languages establishes two

categories: imperative and declarative programming C# or Java are examples of the former, and HTML is a typical declarative syntax (since it's not a language itself) Well, in declarative programming, sentences tend to change the state of the program while using the declarative paradigm, languages indicate only the desired result, with no specifications about how the engine will manage to obtain the results

Serialization

Serialization is the process of translating data structures or the object state into a format that can be stored (for example, in a file or a memory buffer) or transmitted across a network connection and reconstructed later in the same or another computer environment

So, we used to say that serializing an object means to convert its state into a byte stream in such a way that the byte stream can be converted back into a copy of the object Popular text formats emerged years ago and are now well known and accepted, such as XML and JSON, independently of other previous formats (binary included):

DeserializationSerialization

The OS fragments operations among several functional units This is done by

allocating different memory areas for each unit in execution It's important to

distinguish between processes and threads

Each process is given a set of resources by the OS, which—in Windows—means that a process will have its own virtual address space allocated and managed

accordingly When Windows initializes a process, it is actually establishing a context

of execution, which implies a process environment block, also known as PEB and a data structure However, let's make this clear: the OS doesn't execute processes; it only establishes the execution context

A thread is the functional (or working) unit of a process And that is what the OS executes Thus, a single process might have several threads of execution, which is something that happens very often Each thread has its own address space within the resources previously allocated by the creation of the process These resources are shared by all threads linked to the process:

A process with two threads of execution, running on a single processor

Process

Thread #2 Thread #1

as memory and data

Different processes do not share these resources In particular, the threads of a process share its instructions (the executable code) and its context (the values of its variables at any given moment)

Programming languages such as NET languages, Java, or Python expose threading

to the developer while abstracting the platform-specific differences in threading implementations at runtime

Note that communication between threads is possible through the common set of resources initialized by the process creation

Of course, there is much more written about these two concepts, which go far beyond the scope of this book (refer to Wikipedia, https://en.wikipedia.org/wiki/

Thread_(computing), for more details), but the system provides us with mechanisms

to check the execution of any process and also check what the threads in execution are

If you are curious about it or just need to check whether something is going wrong, there are two main tools that I recommend: the Task Manager (included in the operating system, which you'll probably know), and—even better—one of the tools designed by the distinguished engineer and technical fellow Mark Russinowitch, available for free and composed of a set of more than 50 utilities.

Some have a Windows interface and others are console utilities, but all of them are highly optimized and configurable to monitoring and controlling the inner aspects

of our operating system at any moment They are available for free at https://technet.microsoft.com/en-us/sysinternals/bb545021.aspx

If you don't want to install anything else, open Task Manager (just right-click on the task bar to access it) and select the Details tab You will see a more detailed

description of every process, the amount of CPU used by each process, the

memory allocated for each process, and so on You can even right-click on one of the processes and see how there is a context menu that offers a few possibilities, including launching a new dialog window that shows some properties related to it:

If you really want to know how a process behaves in its entirety, the tools to use are SysInternals If you go to the link indicated earlier, you'll see an item menu especially dedicated to process utilities There, you have several choices to work with, but the

most comprehensive are Process Explorer and Process Monitor.

Process Explorer and Process Monitor don't require installation (they're written in

C++), so you can execute them directly from any device for a Windows platform

For example, if you run Process Explorer, you'll see a fully detailed window showing

every single detail of all the processes currently active in the system

With Process Explorer, you can find out what files, registry keys, and other objects

processes have opened, together with the DLLs they have loaded, who owns each process, and so on Every thread is visible and the tool provides you with detailed information, available through a very intuitive user interface:

It's also very useful to check the system's general behavior at real time, since it creates graphics of activities of CPU usage, I/O, Memory, among others, as shown

in the following screenshot:

In a similar way, Process Monitor, focuses on monitoring the filesystem, the

Registry, and all processes and threads with their activities in real time, since it

actually is a mixture of two previous utilities merged together: FileMon (File

Monitor) and RegMon (Registry Monitor), which are not available anymore.

If you try out PM, you'll see some of the information included in PE, plus the specific information provided by PM—just conveyed in a different manner

Static versus dynamic memory

When a program starts execution, the OS assigns a process to it by means of

scheduling: the method by which work specified by some means is assigned to resources that complete the work This means that the resources for the process are assigned, and that implies memory allocation

As we'll see, there are mainly two types of memory allocation:

• Fixed memory (linked to the stack), determined at compile time Local variables are declared and used in the stack Note that it is a contiguous block of memory allocated when the process resources are initially assigned The allocation mechanism is very fast (although the access not so much)

• The other is dynamic memory (the heap), which can grow as the program required it, and it's assigned at runtime This is the place where instance variables are allocated (those that point to an instance of a class or object).Usually, the first type is calculated at compile time since the compiler knows how much memory will be needed to allocate the variables declared depending on its type (int, double, and so on) They are declared inside functions with a syntax such

as int x = 1;

The second type requires the new operator to be invoked Let's say there is a class named Book in our code, we create an instance of such Book with an expression of this type:

Book myBook = new Book();

This instructs the runtime to allocate enough space in the heap to hold an instance

of that type along with its fields; the state of the class is allocated in the heap This means that the whole state of a program will store its state in a different memory (and, optionally, disk) locations

Of course, there are more aspects to account for, which we'll cover in the The Stack

and the Heap section in this chapter Luckily, the IDE lets us watch and analyze all

these aspects (and many more) at debug time, offering an extraordinary debugging experience

Garbage collector

Garbage collection (GC) is a form of automatic memory management The GC in

.NET, attempts to reclaim garbage or the memory occupied by objects that are no longer in use by the program Going back to the previous code declaration of Book, when there are no references to the Book object in the stack, the GC will reclaim that space to the system, liberating memory (it's a bit more complex, in fact, and I'll get into further detail later in this chapter—when we talk about memory management—but let's put it that way for the moment)

It's important to note that garbage collectors are not something exclusive to the NET platform Actually, you can find it in all platforms and programs even if you're dealing with browsers Current JavaScript engines, for instance, such as Chrome's V8, Microsoft's Chakra—and others—use a garbage collection mechanism as well

Concurrent computing

Concurrency or concurrent computing is a very common concept nowadays, and we'll discover it at several instances along this book The official definition in

Wikipedia (https://en.wikipedia.org/wiki/Concurrent_computing) says:

"Concurrent computing is a form of computing in which several computations are executed during overlapping time periods—concurrently—instead of sequentially (one completing before the next starts) This is a property of a system—this may be

an individual program, a computer, or a network—and there is a separate execution point or "thread of control" for each computation ("process") A concurrent system

is one where a computation can advance without waiting for all other computations

to complete; where more than one computation can advance at the same time."

Parallel computing

Parallel computing is a type of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved at the same time .NET offers several variants of this type of computing, which we'll cover over the next few chapters:

Serial Approach Parallel Approach

Start

Stop

workers

Evaluate model Evaluatemodel

Evaluate model

Evaluate model Start

Stop

For k =1 : N

Evaluate model

Imperative programming

Imperative programming is a programming paradigm that describes computation

in terms of the program's state C#, JavaScript, Java, or C++ are typical examples of imperative languages

Declarative programming

In contrast to imperative programming, languages considered declarative describe only the desired results without explicitly listing commands or steps that must be performed Many markup languages, such as HTML, XAML, or XSLT, fall into this category

The evolution of NET

Until the arrival of NET, the Microsoft programming ecosystem had been ruled by a few classic languages, Visual Basic and C++ (with the Microsoft Foundation classes) being typical examples of this

Also known as MFC, Microsoft Foundation Classes is a library

that wraps portions of the Windows API in C++ classes, including

functionalities that enable them to use a default application framework

Classes are defined for many of the handle-managed Windows

objects and also for predefined windows and common controls It was

introduced in 1992 with Microsoft's C/C++ 7.0 compiler for use with

16-bit versions of Windows as an extremely thin object-oriented C++

wrapper for the Windows API

However, the big changes proposed by NET were started using a totally different component model approach Up until 2002, when NET officially appeared, such

a component model was COM (Component Object Model), introduced by the

company in 1993 COM is the basis for several other Microsoft technologies and frameworks, including OLE, OLE automation, ActiveX, COM+, DCOM, the Windows

shell, DirectX, UMDF (User-Mode Driver Framework), and Windows runtime.

A device-driver development platform (Windows Driver Development

Kit) first introduced with Microsoft's Windows Vista operating system

is also available for Windows XP It facilitates the creation of drivers for

certain classes of devices

At the time of writing this, COM is a competitor with another specification named

CORBA (Common Object Request Broker Architecture), a standard defined by

the Object Management Group (OMG), designed to facilitate the communication

of systems that are deployed on diverse platforms CORBA enables collaboration between systems on different operating systems, programming languages, and computing hardware In its life cycle, it has received a lot of criticism, mainly

because of poor implementations of the standard

.NET as a reaction to the Java World

In 1995, a new model was conceived to supersede COM and the unwanted effects related to it, especially versions and the use of the Windows Registry on which COM depends to define accessible interfaces or contracts; a corruption or modified fragment of the registry could indicate that a component was not accessible at runtime Also, in order to install applications, elevated permissions were required, since the Windows Registry is a sensible part of the system

A year later, various quarters of Microsoft started making contacts with some of the most distinguished software engineers, and these contacts remained active over the years These included architects such as Anders Hejlsberg (who became the main author of C# and the principal architect of NET framework), Jean Paoli (one of the signatures in the XML Standard and the former ideologist of AJAX technologies), Don Box (who participated in the creation of SOAP and XML Schemas), Stan

Lippman (one of the fathers of C++, who was working at the time at Disney),

Don Syme (the architect for generics and the principal author of the F# language), and so on

The purpose of this project was to create a new execution platform, free from the caveats of COM and one that was able to hold a set of languages to execute in a secure and extensible manner The new platform should be able to program and integrate the new world of web services, which had just appeared—based on

XML—along with other technologies The initial name of the new proposal was

Next Generation Windows Services (NGWS).

By late 2000, the first betas of NET framework were released, and the first version appeared on February 13, 2002 Since then, NET has been always aligned with new versions of the IDE (Visual Studio) The current version of the classic NET framework at the time of writing this is 4.6.1, but we will get into more detail on this later in the chapter

An alternative NET appeared in 2015 for the first time In the //BUILD/ event, Microsoft announced the creation and availability of another version of NET, called NET Core

The open source movement and NET Core

Part of an idea for the open source movement and NET Core comes from a deep change in the way software creation and availability is conceived in Redmond nowadays When Satya Nadella took over as the CEO at Microsoft, they clearly

shifted to a new mantra: mobile-first, cloud-first They also redefined themselves

as a company of software and services.