c#

[gustavo-fior]

I've been coding in Java for couple of years now, so my notes are gonna be based on the differences between Java and C#

[gustavo-fior]

• https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2008/ms228358(v=vs.90)?redirectedfrom=MSDN (maybe a little old)
• https://learn.microsoft.com/en-us/dotnet/standard/design-guidelines/naming-guidelines
• https://www.youtube.com/watch?v=6SeHv5x_OFA&ab_channel=AnubhavShrivastava
• http://www.25hoursaday.com/CsharpVsJava.html

[gustavo-fior]

• packages -> namespaces
• class.java -> class.cs (can have multiple top-level classes and don't need to match filename)
• extends/implements -> : (for interfaces and abstract classes)
• maven (pom.xml) / gradle (build.gradle) -> NuGet (nuget.config) / MSBuild
• garbage collector works similarly in both
• if, else, and else if are identical
• for, do, and do while are identical

as far as I searched, there's no available version of visual studio (not vs code) for Linux :/

[gustavo-fior]

Packages and namespaces

• you can have multiple classes from multiple namespaces in the same file
• imports -> using and it comes before the namespace declaration
• DataTier is an alias for a class imported from another namespace

using System.IO;
using DataTier = Acme.SQLCode.Client;

namespace AcmeAccounting
{
    public class GetDetails
    {
        // ...
    }
}

namespace AcmeFinance
{
    public class ShowDetails
    {
        // ...
    }
}

[gustavo-fior]

Data types

• c# has automatic boxing and unboxing (which means no int -> Integer or double -> Double)
• every data type name is an alias for a class in the System namespace
• Boolean -> bool

Short Name	.NET Class	Type	Width	Range (bits)
byte	Byte	Unsigned integer	8	0 to 255
sbyte	SByte	Signed integer	8	-128 to 127
int	Int32	Signed integer	32	-2,147,483,648 to 2,147,483,647
uint	UInt32	Unsigned integer	32	0 to 4294967295
short	Int16	Signed integer	16	-32,768 to 32,767
ushort	UInt16	Unsigned integer	16	0 to 65535
long	Int64	Signed integer	64	-9223372036854775808 to 9223372036854775807
ulong	UInt64	Unsigned integer	64	0 to 18446744073709551615
float	Single	Single-precision floating point type	32	-3.402823e38 to 3.402823e38
double	Double	Double-precision floating point type	64	-1.79769313486232e308 to 1.79769313486232e308
char	Char	A single Unicode character	16	Unicode symbols used in text
bool	Boolean	Logical Boolean type	8	True or false
object	Object	Base type of all other types
string	String	A sequence of characters
decimal	Decimal	Precise fractional or integral type that can represent decimal numbers with 29 significant digits	128	±1.0 × 10e−28 to ±7.9 × 10e28

[gustavo-fior]

Constants

• final -> const
• readonly (variables that can be initialized only once, through the constructor or in the declaration)

Enums

• don't need to specify that value (optional)
• .toString() returns the name of the constant

public enum Color
{
    Green,   //defaults to 0
    Orange,  //defaults to 1
    Red,     //defaults to 2
    Blue     //defaults to 3
}  

public enum Color2
{
    Green = 10,
    Orange = 20,
    Red = 30,
    Blue = 40
}

[gustavo-fior]

String

• also immutable
• can compare strings with == (java sucks at this)
• StringBuilder is the equivalent to StringBuffer (adding new string without creating new objects)

• String literals:

  static void Main()
  {
  //Using escaped characters: 
  string path1 = "\\\\FileShare\\Directory\\file.txt";
  System.Console.WriteLine(path1);
  
  //Using String Literals: 
  string path2 = @"\\FileShare\Directory\file.txt";
  System.Console.WriteLine(path2);
  }

[gustavo-fior]

Value and Reference Types

in c# we have:

• value reference

  
  int i = 10;
  int k = i;
  i = 30;

System.Console.WriteLine(i); // 30 System.Console.WriteLine(k); // 10

- **type reference** -> will point to the same object, which means if you made a change through ee2, ee1 will also be updated
```cs
Employee ee1 = new Employee();
Employee ee2 = ee1;

[gustavo-fior]

Operators

• same as Java, just some additions:

Category	Symbol
Type of Operand	typeof
Size of Operand	sizeof
Enforce Overflow Checking	checked
Suppress Overflow Checking	unchecked

[gustavo-fior]

Checked and Unchecked operations

• you can check or uncheck operations that may cause exception

class TestCheckedAndUnchecked
{
    static void Main()
    {
        short a = 10000;
        short b = 10000;

        short c = (short)(a * b);                     // unchecked by default 
        short d = unchecked((short)(10000 * 10000));  // unchecked 
        short e = checked((short)(a * b));            // checked - run-time error

        System.Console.WriteLine(10000 * 10000);  // 100000000
        System.Console.WriteLine(c);              // -7936
        System.Console.WriteLine(d);              // -7936
        System.Console.WriteLine(e);              // no result
    }    
}

[gustavo-fior]

Switches

• you can make switches with strings

• you need to specify what you want to do at the end of the case (e.g. break; or goto case "idk";)

  static void Main(string[] args)
  {
  switch (args[0])
  {
      case "copy":
          //... 
          break;
  
      case "move":
          //... 
          goto case "delete";
  
      case "del":
      case "remove":
      case "delete":
          //... 
          break;
  
      default:
          //... 
          break;
  }
  }

[gustavo-fior]

Foreach

static void Main()
{
    string[] arr= new string[] {"Jan", "Feb", "Mar"};

    foreach (string s in arr)
    {
        System.Console.WriteLine(s);
    }
}

[gustavo-fior]

Access modifiers

• public Visible to all.

• protected Visible only from derived classes.

• private DEFAULT Visible only within the given class.

• internal Visible only within the same assembly.

• protected internal Visible only to the current assembly or types derived from the containing class.

• sealed (structs) The class can´t be inherited.

• readonly / const Create constants like final in Java. Can only assign in constructor or declaration.

[gustavo-fior]

Main method

static int Main(string[] args)
{
    //... 
    return 0;
}

[gustavo-fior]

Passing by reference/value

if a parameter is a primitive, it will be passed as a value, if it's an object it will be passed as a reference. if you want to pass primitives as reference, use keyword out or ref.

[gustavo-fior]

Infinite params in method

• you can pass a indeterminate number of params for a function like this:

  class TestParams
  {
  private static void Average(string title, params int[] values)
  {
      int sum = 0;
      System.Console.Write("Average of {0} (", title);
  
      for (int i = 0; i < values.Length; i+)
      {
          sum += values[i];
          System.Console.Write(values[i] + ", ");
      }
      System.Console.WriteLine("): {0}", (float)sum/values.Length);
  }
  static void Main()
  {
      Average ("List One", 5, 10, 15);
      Average ("List Two", 5, 10, 15, 20, 25, 30);
  }
  }