C, C++, and C# are all programming languages, but they differ in their syntax, features, and areas of application.

Programming in C#

Useful DOTNET Console Commands

> dotnet --help {show command line help}
> dotnet --info {display .NET information}
> dotnet --list-runtimes {display the installed runtimes}
> dotnet --list-sdks {display installed SDKs}
> dotnet --version {display .NET version information}
> dotnet new console {create new console application}

Create a new console application

For .NET versions below 6.0, the Program.cs is generated with the following template:

using System; // Use code in the .NET system 'namespace'

namespace project // Note: actual namespace depends on the project name.
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!"); // Console object is a terminal in the systen namespace
        }
    }
}

...however, for .NET 6 and above, the template is much simpler...

// See https://aka.ms/new-console-template for more information
Console.WriteLine("Hello, World!");

When you use this newer version, you only need to write the body of the Main method. The compiler synthesizes a Program class with a Main method and places all your top level statements in that Main method. You don't need to include the other program elements, the compiler generates them for you. You can still use the old program structure - the compiler doesn't need to generate the extra elements, is all.

Namespaces

Namespaces help organise programs and present names that are in your code from 'colliding' with names in other programs that you may be using or with names in the .NET programs themselves.

Classes

All C# programs are organised in classes.

The Main function

Each C# console has an entry point and that entry point is named Main. When .NET starts up a program, it looks for the Main entry point and begins execution there. The Main function has no return value (void). The string[] array takes any command line arguments that the app was started with and organises them in an array.

Variable types

int | 4 bytes | Stores whole numbers from -2,147,483,648 to 2,147,483,647 | int i = 10;
long (8 bytes) Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 | long myNum = 15000000000l;
float | 3 bytes | Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits | float f = 2.0f;
double | 8 bytes | Stores fractional numbers. Sufficient for storing 15 decimal digits | double d = 19.999d;
bool | 1 bit | Stores true or false values | bool valid = true;
char | 2 bytes | Stores a single character/letter, surrounded by single quotes | char c = 'c';
string | 2 bytes per character | Stores a sequence of characters, surrounded by double quotes | string s = "this is a string";

You can specify the type of variable. For example...

int i = 10;
float f = 2.0f;
decimal d = 10.0m;
bool b = true;
char c = 'c';
string str = "a string";

...although you can also let the compiler figure out what variable type using the var keyword.

var x = 10;
var z = "Hello!";

Arrays

Can be single dimensional, multi-dimensional or jagged