Introduction

It’s like an old tradition to introduce new programming language to the readers using a ‘Hello World!’ program, so keeping that in mind here are the steps to create your first Hello World program in C# and a step by step explanation of each line and keyword used in the program. We also have some examples where we would be consuming C# code in PowerShell and executing it. This approach makes it easy for the reader to understand both these languages and also use them together.

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Table of Contents

 

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C# Types

  • A Data type is an attribute that tells the compiler how to use and represent the data in memory.

  • C# is a strongly-typed language

  • That means we must declare the type of a variable that indicates the kind of values it is going to store, such as integer, float, decimal, text, etc

  • This is also known as Type Declaration

    PowerShell Example:

    $str = "hello world!"
$str.GetType()

    C# Example:

    string str = "hello world!";
str.GetType()

All C# data types or simply ‘types’ can be classified into two broad categories:

  1. Value types
  2. Reference types
C# Data Types Tree

  1. Values Types

      • Holds a value within its own designated memory space
      • Can not contain null values
      • Derived from base class [System.ValueType]

    Following is a list of value data types you can use in your C# programs.

    .Net Type Type Alias Represents Range Default Value
    System.Byte byte 8-bit unsigned integer 0 to 255 0
    System.Boolean bool Boolean value True or False False
    System.Char char 16-bit Unicode character U+0000 to U+ffff ‘\0’
    System.Decimal decimal 128-bit precise decimal values with 28-29 significant digits (+/-)1.0 x 10^-28 to (+/-)7.9 x 10^28 0.0M
    System.Double double 64-bit double-precision floating point type (+/-)5.0 x 10^-324 to (+/-)1.7 x 10^308 0.0D
    System.Single float 32-bit single-precision floating point type (+/-)1.5 x 10^-45 to (+/-)3.4 x 1038 0.0F
    System.Int32 int 32-bit signed integer type -2,147,483,648 to 2,147,483,647 0
    System.Int64 long 64-bit signed integer type -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 0L
    System.SByte sbyte 8-bit signed integer type -128 to 127 0
    System.Int16 short 16-bit signed integer type -32,768 to 32,767 0
    System.UInt32 uint 32-bit unsigned integer type 0 to 4,294,967,295 0
    System.UInt64 ulong 64-bit unsigned integer type 0 to 18,446,744,073,709,551,615 0
    System.UInt16 ushort 16-bit unsigned integer type 0 to 65,535 0

  2. Reference Types

      • Contain references to other objects or memory locations

      • Actual data is not stored in a variable.

      • One or more variables can reference a single object, and any action performed by anyone variable changes the referenced object.

PowerShell Example:

$str = "This is a string"
$str.GetType() # reference type

$str[1].GetType() # value type

C# Example:

string str = "This is a string";
str.GetType() // reference type

str[1].GetType() // value type
    • Derived from base class [System.Object]

    • C# provides some built-in reference types such as: dynamic, object, string.

    • You can create custom reference types using keywords:

      • class
      • interface
      • delegate
      • string
add-type @"
public class TestDataType {
   public string First;
   public string Last;
   public string Phone;
}
"@
[TestDataType] @{First="Prateek";Last="Singh"}

$Object = [TestDataType] @{First="Prateek";Last="Singh"}
$Object.GetType()

Value vs Reference Types

Value type Reference type
Stores Actual value Memory location \ Reference to a value
Allocation Stack Heap
Lifetime Lifetime of variable Managed by .Net
Nullable Always has value Maybe null
Default 0 null
Assignment Copying actual data Copying reference

Type Conversions

PowerShell Example:

# float to int
[int] 3.14159

# string to char array
[char[]] 'prateek'

# int to char
[char] 97
[char] 98

# bool to int
[int] $true
[int] $false

# int to bool
[bool] 1
[bool] 0

# char to int
[int] [char]'Z'

# int to hex
"{0:x}" -f 397312

C# Examples:

// float to int
(int) 3.14159

// string to char array
"prateek".ToCharArray()

// int to char
(char) 97
(char) 98

// bool to int
(int) true // throws error - Cannot convert type 'bool' to 'int
true ? 1 : 0 // alternatively, use ternary operator

// char to int
(int) 'Z'

// int to hex
Convert.ToString(397312,16)
Convert.ToInt32(Convert.ToString(397312,16))

Type Conversion

C# Variables

  • A variable is the name of the storage location to store values of data types supported by the programming language.

  • In C# depending upon the data type of the variable, a memory location with a specific size and layout is assigned to the variable.

To define and initialize a variable we follow the below-mentioned syntax:

// variable definition
<data-type> <variable-name>;

// multiple variable definition
<data-type> <variable-name1>, <variable-name2>, <variable-name3>; 

// variable definition and initialization
<data-type> <variable-name> = value;

Here, <data-type> can be one of the data types that we discussed in the previous subsection such as value types: char,int,float and reference types or in other words a user-defined data types: Employee, Car etc. Following are some examples to demonstrate this:

public class example
{
    static void Main(string[] args)
    {
        // single variable declaration only
        bool flag;

        // multiple variable declaration only
        int a, b, c;

        // variable declaration and initialization
        double pi = 3.14;
        char chr = 'a';
        int num, count = 5;
        int[] list = { 2, 4, 6, 8, 10 };
    }
}

When declaring a variable in your C# program, you must explicitly specify the data type, otherwise, you can also use the ’var’ keyword to let the compiler implicitly decide the type of a variable at compilation time.

Var datatype was introduced in C# 3.0. var is used to declare implicitly typed local variable means it tells the compiler to figure out the type of the variable at compilation time.

var i = 0;

C# Operators, Operands and Expressions

Expressions are combinations or sequences of operands and operators and once an expression is evaluated, it returns a value.

The operators of expression represent operations to apply to the operands. For example: (x + y) * z is an expression in which x, y, z are operands and +, * are operators.

Operators

The operators in the C# Language can be categorized into, following 3 broad categories:

  1. Unary operator

    Unary operators take one operand to perform the operation and either prefixed or postfixed to the operand. Some common use cases can be increment (++), decrement (--) and negative boolean (!) operators, below are some examples that will help you understand.

    PowerShell Example:

    # increment and decrement operators
$x = 5;
(++$x) # pre increment operator
($x++) # post increment operator
(--$x) # pre decrement operator
($x--) # post decrement operator

# negative boolean operator
[bool] $flag = $true;
!$flag # alternatively, -not $flag
!$false
!$true

    C# Example:

    // increment and decrement operators
int x = 5;
++x // pre increment operator
x++ // post increment operator
--x // pre decrement operator
x-- // post decrement operator

// negative boolean operator
bool flag = true;
!flag
!false
!true

  2. Binary operator

    Binary operators take two operands to perform the operation and operator is in between the two operands,

    • Arithmetic Operators: (+, -, *, /, %)
    • Logical Operators: OR (||) and logical AND (&&) operators.
    • Relation Operators: (>, >=, <, <=, ==, !=)
    • Assignment Operators: (=)

    PowerShell Example:

    # arithmetic operators
1 + 2
13 - 12
5 * 5
15 / 3
29 % 4

# logical operators
$x = $true;
$y = $false;
$x -or $y
$x -and $y

    C# Example:

    // arithmetic operators
1 + 2
13 - 12
5 * 5
15 / 3
29 % 4

// logical operators
var x = true;
var y = false;
x || y
x && y

    PowerShell Example:

    # relational operators
1 -gt 0
"ONE" -eq "one"
5 -le 5
2 -ne 5

# assignment operators
[int] $x, $y
$x = 5
$y = $x + 3

    C# Example:

    // relational operators
1 > 0
"ONE" == "one"
5 <= 5
2 != 5

// assignment operators
int x, y;
x = 5
y = x + 3

  3. Ternary operator

A special operator that is used in decision making or to check conditions, this operator takes three operands.

Syntax:

<condition> ? <if true> : <if false>

PowerShell Example:

[int] $x = 5;
[int] $y = 7;

$x -gt $y ? "x greater-than y" : "x smaller-than y"

C# Example:

int x = 5;
int y = 7;

x > y ? "x greater-than y" : "x smaller-than y"

Video Tutorial

[02:22]PowerShell to C# and Back – Comments, Case sensitivity, Using directive
{ Presented by Deepak Dhami [Twitter] [Blog] }

[30:55] PowerShell to C# and Back –  Types, Type Conversion, Variables and Operators
{ Presented by Prateek Singh [Twitter] [Blog] }

  • C# Types
    • Value Types
    • Reference Types
  • Value vs Reference Types
  • Type Conversions
  • C# Variables
  • C# Operators
    • Unary operator
    • Binary operator
    • Ternary operator

 

Optical Character Recognition
Author of “PowerShell Guide to Python“, “Windows Subsystem for Linux (WSL)” and currently writing the most awaited book: “PowerShell to C# and Back” !

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