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The C# Definitive Guide

The C# Definitive Guide

17 Nov 2018 #tutorial #csharp

Are you looking for a learning path to be “fluent” in C#? This is the right place for you! This is my definitive guide to what every beginner and intermediate C# developer should know.

Every intermediate C# developer should know how to productively work with Visual Studio or Visual Studio Code, use async/await keywords, most common LINQ methods and regular expressions. Also, to get around large codebases and be aware of the latest C# features.

1. Environment

Visual Studio is the de-facto Integrated Development Environment (IDE) for C#. Since we will spend most of our workdays with Visual Studio, we should setup Visual Studio to make use more productive.

For more settings and extensions, check my Visual Studio setup for C#.

The C# Definitive Guide
Have everything ready to level up your C#. Photo by Andrew Neel on Unsplash

2. Git and Github

Git

Git is a version control system. A time machine to go back in time, create alternate stories from a point in time and make alternate stories join our present. You got the analogy?

If we are creating a zip file with our code and naming it after the date of our latest change, Git is a better way.

GitHub

Programming is about collaboration. GitHub is the social network for programmers.

With GitHub, we can show our own code, ask for new features in a library, and report bugs in the software we use.

Microsoft, Facebook, Google have some of their own code available on GitHub.

3. Design Patterns and Object-Oriented Design Principles

Desing patterns are recipes to solve common problems in code. This is, given a certain problem, there is a blueprint or an outline that will help us to solve that problem.

4. Dealing with large codebases

Programming is also about reading code. Get used to navigate throught large codebases.

For more guidelines about reading code, check Changelog’s One sure-fire way to improve your coding.

5. Unit tests

A unit test is a “safety net” to make sure we don’t break things when we add new features or modify our codebase. A unit test is a piece of code that uses our code base from a “user” point of view and verifies a given behavior.

6. LINQ

Language-Integrated Query, LINQ, is the declarative way to work with collections in C# or anything that looks like one. Instead of writing foreach, for or while loops to work with collections, let’s give LINQ a try.

7. Regular Expressions

Have you ever used *.txt in the file explorer to find all text files in a folder? If so, we have already used regular expressions. But, *.txt is just the tip of the iceberg.

Regular expressions give us a search syntax to find patterns of text in a string. For example, to find all phone numbers like this one (+57) 3XX XXX-XXX, let’s use (\(\+\d{2}\))\s(\d{3})\s(\d{3})\-(\d{3}).

8. async/await

Asyncronous code is code that doesn’t block when executing long-running operations.

9. New C# features

C# is an evolving language. With every new version, we have more features to write more concise code. These are some of the new features in C# since C# 6.0.

String interpolation

Before we wrote,

string.Format("Hello, {0}", name);

Now we can write,

$"Hello, {name}";

Null-conditional operators

There are two new operators to check for null values: ?? and ?..

Before,

string name = ReadNameFromSomewhere();
if (name == null)
    name = "none";
else
    name.Trim();

After,

string name = ReadNameFromSomewhere();
name?.Trim() ?? "none"

Inlined out variables

Now, we can inline the variable declaration next to the out keyword.

Before,

int count = 0;
int.TryParse(readFromKey, out count);

After,

int.TryParse(readFromKey, out var count)

Or even,

int.TryParse(readFromKey, out _)

Using declarations

A variable preceded by using is disposed at the end of the scope.

Before,

using (var reader = new StreamReader(fileName))
{
    string line; 
    while ((line = reader.ReadLine()) != null)  
    {  
        // Do something  
    }  
}

After,

using var reader = new StreamReader(fileName);

string line; 
while ((line = reader.ReadLine()) != null)  
{  
    // Do something  
}

Nullable reference types

All reference variables are non-nullable by default. Any attempt to dereference a nullable reference gets a warning from the compiler. Goodbye, NullReferenceException!

We need to turn on this feature at the project level in our csproj files.

Before,

int notNull = null;
//  ^^^^^
// error CS0037: Cannot convert null to 'int'
int? canBeNull = null;

string name = null;
SayHi(name);
// ^^^^^
// System.NullReferenceException

void SayHi(string name) => Console.WriteLine(name.Trim());

After,

string name = null;
// ^^^^^
// warning CS8600: Converting null literal or possible null value to non-nullable type.

string? canBeNullName = null;
SayHi(name);
// ^^^^^
// warning CS8604: Possible null reference argument for parameter 'name'

To learn other techniques to prevent the NullReferenceException, start checking what the NullReferenceException is and when it’s thrown.

Records

A record is an immutable reference type with built-in equality methods. When we create a record, the compiler creates a ToString method, a value-based equality methods and other methods for us.

public record Movie(string Title, string ReleaseYear);

Top-level statements

All the boilerplate is now gone from Main methods.

Before,

using System;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}

After,

Console.WriteLine("Hello World!");

To learn about other C# features, check my top 10 or so best C# features.

10. Bonus Points

Voilà! That’s my take on what every intermediate C# developer should know! Don’t be overwhelm by the amount of things to learn. Don’t try to learn everything at once, either. Learn one subject at a time! And, start using it in your every day coding as you learn it.

If you want to write more expressive code to work with collections, check my course Getting Started with LINQ on Educative, where I cover from what LINQ is, to refactoring conditionals with LINQ and to the its new methods and overloads in .NET6. All you need to know to start using LINQ in your everyday coding.

Happy coding!

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