See Sharp Cheat Sheet by Kemmojoo

// Single line
/* Multiple
line */
/// XML comments on single line
/* XML comments on multiple lines /

enum Action {Start, Stop, Rewind, Forward};
enum Status {Flunk = 50, Pass = 70, Excel = 90};

Action a = Action.Stop;
if (a != Action.Start)
//Prints "Stop is 1"
  System.Console.WriteLine(a + " is " + (int) a);
 
// Prints 70
System.Console.WriteLine((int) Status.Pass);
// Prints Pass
System.Console.WriteLine(Status.Pass);

enum Weekdays{
  Saturday, Sunday, Monday, Tuesday, Wednesday, Thursday, Friday
}

delegate void MsgArrivedEventHandler(string message);
 
event MsgArrivedEventHandler MsgArrivedEvent;
 
//Delegates must be used with events in C#
 
MsgArrivedEvent += new MsgArrivedEventHandler
  (My_MsgArrivedEventCallback);
//Throws exception if obj is null
MsgArrivedEvent("Test message");
MsgArrivedEvent -= new MsgArrivedEventHandler
  (My_MsgArrivedEventCallback);
 
using System.Windows.Forms;
 
Button MyButton = new Button();
MyButton.Click += new System.EventHandler(MyButton_Click);

private void MyButton_Click(object sender, System.EventArgs e) {
  MessageBox.Show(this, "Button was clicked", "Info",
    MessageBoxButtons.OK, MessageBoxIcon.Information);
}

//Pre-test Loops: while (i < 10)
  i++;
for (i = 2; i < = 10; i += 2)
  System.Console.WriteLine(i);


//Post-test Loop:
do
  i++;
while (i < 10);

// Array or collection looping
string[] names = {"Steven", "SuOk", "Sarah"};
foreach (string s in names)
  System.Console.WriteLine(s);

TopAuthor author = new TopAuthor();
 
//No "With" construct
author.Name = "Steven";
author.AuthorRanking = 3;
 
author.Rank("Scott");
TopAuthor.Demote() //Calling static method
 
TopAuthor author2 = author //Both refer to same object
author2.Name = "Joe";
System.Console.WriteLine(author2.Name) //Prints Joe
 
author = null //Free the object
 
if (author == null)
  author = new TopAuthor();
 
Object obj = new TopAuthor(); 
if (obj is TopAuthor)
  SystConsole.WriteLine("Is a TopAuthor object.");

namespace ASPAlliance.DotNet.Community {
  ...
}
 
// or
 
namespace ASPAlliance {
  namespace DotNet {
    namespace Community {
      ...
    }
  }
}

using ASPAlliance.DotNet.Community;

using System
Namespace MyNameSpace{
  class HelloWorld  {     
    static void Main(string[] args)    {
      System.Console.WriteLine("Hello World")
    }
  }
}

//Escape sequences
\n, \r
\t
\\
\
 
Convert.ToChar(65) //Returns 'A' - equivalent to Chr(num) in VB
// or
(char) 65
 
System.Console.Write("What's your name? ");
string name = SYstem.Console.ReadLine();
System.Console.Write("How old are you? ");
int age = Convert.ToInt32(System.Console.ReadLine());
System.Console.WriteLine("{0} is {1} years old.", name, age);
//or
System.Console.WriteLine(name + " is " + age + " years old.");
 
int c = System.Console.Read(); //Read single char
System.Console.WriteLine(c); //Prints 65 if user enters "A"

//Comparison
==  <  >  <=  >=  !=
 
//Arithmetic
+  -  *  /
%  (mod)
/  (integer division if both operands are ints)
Math.Pow(x, y)
 
//Assignment
=  +=  -=  *=  /=   %=  &=  |=  ^=  <<=  >>=  ++  --
 
//Bitwise
&  |  ^   ~  <<  >>
 
//Logical
&&  ||   !
 
//String Concatenation
+

struct AuthorRecord {
  public string name;
  public float rank;
 
  public AuthorRecord(string name, float rank) {
    this.name = name;
    this.rank = rank;
  }
}

AuthorRecord author = new AuthorRecord("Steven", 8.8);
AuthorRecord author2 = author
 
author.name = "Scott";
SystemConsole.WriteLine(author.name); //Prints Steven
System.Console.WriteLine(author2.name); //Prints Scott

// Pass by value (in, default), reference
//(in/out), and reference (out)
void TestFunc(int x, ref int y, out int z) {
  x++;
  y++;
  z = 5;
}
 
int a = 1, b = 1, c; // c doesn't need initializing
TestFunc(a, ref b, out c);
System.Console.WriteLine("{0} {1} {2}", a, b, c); // 1 2 5
 
// Accept variable number of arguments
int Sum(params int[] nums) {
  int sum = 0;
  foreach (int i in nums)
    sum += i;
  return sum;
}
 
int total = Sum(4, 3, 2, 1); // returns 10
 
/* C# doesn't support optional arguments/parameters.
Just create two different versions of the same function. */
void SayHello(string name, string prefix) {
  System.Console.WriteLine("Greetings, " + prefix + " " + name);
}
 
void SayHello(string name) {
  SayHello(name, "");
}

using System.IO;

//Write out to text file
StreamWriter writer = File.CreateText
  ("c:\\myfile.txt");
writer.WriteLine("Out to file.");
writer.Close();
 
//Read all lines from text file
StreamReader reader = File.OpenText
  ("c:\\myfile.txt");
string line = reader.ReadLine();
while (line != null) {
  Console.WriteLine(line);
  line = reader.ReadLine();
}
reader.Close();
 
//Write out to binary file
string str = "Text data";
int num = 123;
BinaryWriter binWriter = new BinaryWriter(File.OpenWrite
  ("c:\\myfile.dat"));
binWriter.Write(str);
binWriter.Write(num);
binWriter.Close();
 
//Read from binary file
BinaryReader binReader = new BinaryReader(File.OpenRead
  ("c:\\myfile.dat"));
str = binReader.ReadString();
num = binReader.ReadInt32();
binReader.Close();

//Accessibility keywords
public
private
internal
protected
protected internal
static
 
 
//Inheritance
class Articles: Authors {
  ...
}
 
using System;
 
interface IArticle{
  void Show();
}
 
 
class IAuthor:IArticle{
  public void Show()  {
    System.Console.WriteLine("Show() method Implemented");
  }
 
 
  public static void Main(string[] args)  {
    IAuthor author = new IAuthor();
    author.Show();
  }
}

int[] nums = {1, 2, 3};
for (int i = 0; i < nums.Length; i++)
  Console.WriteLine(nums[i]);
 

// 5 is the size of the array
string[] names = new string[5];
names[0] = "Steven";
// Throws System.IndexOutOfRangeException
names[5] = "Sarah"
 

// C# can't dynamically resize an array.
//Just copy into new array.
string[] names2 = new string[7];
// or names.CopyTo(names2, 0);
Array.Copy(names, names2, names.Length);
 
float[,] twoD = new float[rows, cols];
twoD[2,0] = 4.5;
 
int[][] jagged = new int[3][] {
  new int[5], new int[2], new int[3] };
jagged[0][4] = 5;

//Value Types
bool
byte, sbyte
char (example: 'A')
short, ushort, int, uint, long, ulong
float, double
decimal
DateTime

//Reference Types
object
string

int x;
Console.WriteLine(x.GetType())
Console.WriteLine(typeof(int))
 
//Type conversion
float d = 3.5;
int i = (int) d

class TopAuthor {
  private int _topAuthor;
 
  public TopAuthor() {
     _topAuthor = 0;
  }
 
  public TopAuthor(int topAuthor) {
    this._topAuthor= topAuthor
  }
 
  ~TopAuthor() {
    // Destructor code to free unmanaged resources.
    // Implicitly creates a Finalize method
  }
}

class  Withfinally{
  public static void Main() {
    try {
      int x = 5;
      int y = 0;
      int z = x/y;
      Console.WriteLine(z);
    } catch(DivideByZeroException e) {
      System.Console.WriteLine("Error occurred");
    } finally {
      System.Console.WriteLine("Thank you");
    }
  }
}

private int _size;
 
public int Size {
  get {
    return _size;
  }
  set {
    if (value < 0)
      _size = 0;
    else
      _size = value;
  }
}
 
foo.Size++;

using System;
class Date{
    public int Day{
        get {
            return day;
        }
        set {
            day = value;
        }
    }
    int day;
 
 
    public int Month{
        get {
            return month;
        }
        set {
            month = value;
        }
    }
    int month;
 
 
    public int Year{
        get {
            return year;
        }
        set {
            year = value;
        }
    }
    int year;
 
 
    public bool IsLeapYear(int year)    {
        return year%4== 0 ? true: false;
    }
    public void SetDate (int day, int month, int year)    {
        this.day   = day;
        this.month = month;
        this.year  = year;
    }
}

greeting = age < 20 ? "What's up?" : "Hello";

if (x != 100 && y < 5){
  // Multiple statements must be enclosed in {}
  x *= 5;
  y *= 2;
}

if (x > 5)
  x *= y;
else if (x == 5)
  x += y;
else if (x < 10)
  x -= y;
else
  x /= y;

//Must be integer or string
switch (color){
  case "black":
  case "red":    r++;
   break;
  case "blue"
   break;
  case "green": g++;  
   break;
  default:    other++;
   break;
}

const int MAX_AUTHORS = 25;
readonly float MIN_RANKING = 5.00;