|
|
' Single line only
Rem Single line only |
// Single line
/* Multiple
line */
/// XML comments on single line
/** XML comments on multiple lines */ |
|
|
| Value Types
Boolean
Byte
Char (example: "A"c)
Short, Integer, Long
Single, Double
Decimal
Date Reference Types
Object
String
Dim x As Integer
Console.WriteLine(x. GetType ()) ' Prints System.Int32
Console.WriteLine( GetType (Integer)) ' Prints System.Int32
Console.WriteLine( TypeName (x)) ' Prints Integer ' Type conversion
Dim d As Single = 3.5
Dim i As Integer = CType (d, Integer) ' set to 4 (Banker's rounding)
i = CInt (d) ' same result as CType
i = Int (d) ' set to 3 (Int function truncates the decimal) |
Value Types
bool
byte, sbyte
char (example: 'A')
short, ushort, int, uint, long, ulong
float, double
decimal
DateTime (not a built-in C# type) Reference Types
object
string
int x;
Console.WriteLine(x. GetType ()); // Prints System.Int32
Console.WriteLine( typeof (int)); // Prints System.Int32
Console.WriteLine(x. GetType().Name ); // prints Int32
// Type conversion
float d = 3.5f;
int i = (int) d; // set to 3 (truncates decimal)
|
|
|
| Const MAX_STUDENTS As Integer = 25 ' Can set to a const or var; may be initialized in a constructor
ReadOnly MIN_DIAMETER As Single = 4.93 |
const int MAX_STUDENTS = 25; // Can set to a const or var; may be initialized in a constructor
readonly float MIN_DIAMETER = 4.93f; |
|
|
Enum Action
Start
[Stop] ' Stop is a reserved word
Rewind
Forward
End Enum
Enum Status
Flunk = 50
Pass = 70
Excel = 90
End Enum
Dim a As Action = Action.Stop
If a <> Action.Start Then _
Console.WriteLine(a.ToString & " is " & a) ' Prints "Stop is 1"
Console.WriteLine(Status.Pass) ' Prints 70
Console.WriteLine(Status.Pass.ToString()) ' Prints Pass |
enum Action {Start, Stop, Rewind, Forward};
enum Status {Flunk = 50, Pass = 70, Excel = 90};
Action a = Action.Stop;
if (a != Action.Start)
Console.WriteLine(a + " is " + (int) a); // Prints "Stop is 1"
Console.WriteLine((int) Status.Pass); // Prints 70
Console.WriteLine(Status.Pass); // Prints Pass |
|
|
| Comparison
= < > <= >= <> Arithmetic
+ - * /
Mod
\ (integer division)
^ (raise to a power) Assignment
= += -= *= /= \= ^= <<= >>= &= Bitwise
And Or Not << >> Logical
AndAlso OrElse And Or Xor Not Note: AndAlso and OrElse perform short-circuit logical evaluations String Concatenation
& + |
Comparison
== < > <= >= != Arithmetic
+ - * /
% (mod)
/ (integer division if both operands are ints)
Math.Pow(x, y) Assignment
= += -= *= /= %= &= |= ^= <<= >>= ++ -- Bitwise
& | ^ ~ << >> Logical
&& || & | ^ ! Note: && and || perform short-circuit logical evaluations String Concatenation
+ |
|
|
| greeting = IIf (age < 20, "What's up?", "Hello") ' One line doesn't require "End If"
If age < 20 Then greeting = "What's up?"
If age < 20 Then greeting = "What's up?" Else greeting = "Hello" ' Use : to put two commands on same line
If x <> 100 And y < 5 Then x *= 5 : y *= 2 ' Preferred
If x <> 100 And y < 5 Then
x *= 5
y *= 2
End If ' To break up any long single line use _
If whenYouHaveAReally < longLine And _
itNeedsToBeBrokenInto2 > Lines Then _
UseTheUnderscore(charToBreakItUp) ' If x > 5 Then
x *= y
ElseIf x = 5 Then
x += y
ElseIf x < 10 Then
x -= y
Else
x /= y
End If Select Case color ' Must be a primitive data type
Case "pink", "red"
r += 1
Case "blue"
b += 1
Case "green"
g += 1
Case Else
other += 1
End Select |
greeting = age < 20 ? "What's up?" : "Hello"; if (age < 20)
greeting = "What's up?";
else
greeting = "Hello"; // Multiple statements must be enclosed in {}
if (x != 100 && y < 5) {
x *= 5;
y *= 2;
}
No need for _ or : since ; is used to terminate each statement.
if (x > 5)
x *= y;
else if (x == 5)
x += y;
else if (x < 10)
x -= y;
else
x /= y;
// Every case must end with break or goto case
switch (color) { // Must be integer or string
case "pink":
case "red": r++; break;
case "blue": b++; break;
case "green": g++; break;
default: other++; break; // break necessary on default
}
|
|
|
| Pre-test Loops: |
While c < 10
c += 1
End While |
Do Until c = 10
c += 1
Loop |
Do While c < 10
c += 1
Loop |
For c = 2 To 10 Step 2
Console.WriteLine(c)
Next |
Post-test Loops: |
Do
c += 1
Loop While c < 10 |
Do
c += 1
Loop Until c = 10 |
' Array or collection looping
Dim names As String() = {"Fred", "Sue", "Barney"}
For Each s As String In names
Console.WriteLine(s)
Next ' Breaking out of loops
Dim i As Integer = 0
While (True)
If (i = 5) Then Exit While
i += 1
End While
' Continue to next iteration
For i = 0 To 4
If i < 4 Then Continue For
Console.WriteLine(i) ' Only prints 4
Next |
Pre-test Loops: // no "until" keyword
while (c < 10)
c++;
for (c = 2; c <= 10; c += 2)
Console.WriteLine(c);
Post-test Loop:
do
c++;
while (c < 10);
// Array or collection looping
string[] names = {"Fred", "Sue", "Barney"};
foreach (string s in names)
Console.WriteLine(s);
// Breaking out of loops
int i = 0;
while (true) {
if (i == 5)
break;
i++;
} // Continue to next iteration
for (i = 0; i < 5; i++) {
if (i < 4)
continue;
Console.WriteLine(i); // Only prints 4
} |
|
|
| Dim nums () As Integer = {1, 2, 3}
For i As Integer = 0 To nums.Length - 1
Console.WriteLine(nums(i))
Next
' 4 is the index of the last element, so it holds 5 elements
Dim names(4) As String
names(0) = "David"
names(5) = "Bobby" ' Throws System.IndexOutOfRangeException
' Resize the array, keeping the existing values (Preserve is optional)
ReDim Preserve names(6)
Dim twoD(rows-1, cols-1) As Single
twoD(2, 0) = 4.5
Dim jagged ()() As Integer = { _
New Integer(4) {}, New Integer(1) {}, New Integer(2) {} }
jagged(0)(4) = 5
|
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] = "David";
names[5] = "Bobby"; // Throws System.IndexOutOfRangeException
// C# can't dynamically resize an array. Just copy into new array.
string[] names2 = new string[7];
Array.Copy(names, names2, names.Length); // or names.CopyTo(names2, 0); float [,] twoD = new float[rows, cols];
twoD[2,0] = 4.5f; int [][] jagged = new int[3][] {
new int[5], new int[2], new int[3] };
jagged[0][4] = 5; |
|
|
| ' Pass by value (in, default), reference (in/out), and reference (out)
Sub TestFunc( ByVal x As Integer, ByRef y As Integer, ByRef z As Integer)
x += 1
y += 1
z = 5
End Sub Dim a = 1, b = 1, c As Integer ' c set to zero by default
TestFunc(a, b, c)
Console.WriteLine("{0} {1} {2}", a, b, c) ' 1 2 5 ' Accept variable number of arguments
Function Sum(ByVal ParamArray nums As Integer()) As Integer
Sum = 0
For Each i As Integer In nums
Sum += i
Next
End Function ' Or use Return statement like C#
Dim total As Integer = Sum(4, 3, 2, 1) ' returns 10 ' Optional parameters must be listed last and must have a default value
Sub SayHello(ByVal name As String, Optional ByVal prefix As String = "")
Console.WriteLine("Greetings, " & prefix & " " & name)
End Sub
SayHello("Strangelove", "Dr.")
SayHello("Madonna")
|
// 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);
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) {
Console.WriteLine("Greetings, " + prefix + " " + name);
}
void SayHello(string name) {
SayHello(name, "");
} |
|
|
| Special character constants
vbCrLf, vbCr, vbLf, vbNewLine
vbNullString
vbTab
vbBack
vbFormFeed
vbVerticalTab
"" ' String concatenation (use & or +)
Dim school As String = "Harding" & vbTab
school = school & "University" ' school is "Harding (tab) University" ' Chars
Dim letter As Char = school.Chars(0) ' letter is H
letter = Convert.ToChar(65) ' letter is A
letter = Chr (65) ' same thing
Dim word() As Char = school.ToCharArray() ' word holds Harding ' No string literal operator
Dim msg As String = "File is c:\temp\x.dat"
' String comparison
Dim mascot As String = "Bisons"
If (mascot = "Bisons") Then ' true
If (mascot. Equals ("Bisons")) Then ' true
If (mascot. ToUpper (). Equals ("BISONS")) Then ' true
If (mascot. CompareTo ("Bisons") = 0) Then ' true Console.WriteLine(mascot.Substring(2, 3)) ' Prints "son" ' String matching
If ("John 3:16" Like "Jo[Hh]? #:*") Then 'true
Imports System.Text.RegularExpressions ' More powerful than Like
Dim r As New Regex ("Jo[hH]. \d:*")
If (r.Match("John 3:16").Success) Then 'true ' My birthday: Oct 12, 1973
Dim dt As New DateTime(1973, 10, 12)
Dim s As String = "My birthday: " & dt.ToString("MMM dd, yyyy") ' Mutable string
Dim buffer As New System.Text. StringBuilder ("two ")
buffer.Append("three ")
buffer.Insert(0, "one ")
buffer.Replace("two", "TWO")
Console.WriteLine(buffer) ' Prints "one TWO three" |
Escape sequences
\n, \r
\t
\\
\"
// String concatenation
string school = "Harding\t";
school = school + "University"; // school is "Harding (tab) University" // Chars
char letter = school[0]; // letter is H
letter = Convert.ToChar(65); // letter is A
letter = (char) 65; // same thing
char[] word = school.ToCharArray(); // word holds Harding // String literal
string msg = @ "File is c:\temp\x.dat";
// same as
string msg = "File is c:\\temp\\x.dat";
// String comparison
string mascot = "Bisons";
if (mascot == "Bisons") // true
if (mascot. Equals ("Bisons")) // true
if (mascot. ToUpper (). Equals ("BISONS")) // true
if (mascot. CompareTo ("Bisons") == 0) // true Console.WriteLine(mascot. Substring (2, 3)); // Prints "son" // String matching
// No Like equivalent - use regular expressions
using System.Text.RegularExpressions;
Regex r = new Regex (@"Jo[hH]. \d:*");
if (r.Match("John 3:16").Success) // true // My birthday: Oct 12, 1973
DateTime dt = new DateTime(1973, 10, 12);
string s = "My birthday: " + dt.ToString("MMM dd, yyyy"); // Mutable string
System.Text. StringBuilder buffer = new System.Text. StringBuilder ("two ");
buffer. Append ("three ");
buffer. Insert (0, "one ");
buffer. Replace ("two", "TWO");
Console.WriteLine(buffer); // Prints "one TWO three" |
|
|
| ' Throw an exception
Dim ex As New Exception("Something is really wrong.")
Throw ex ' Catch an exception
Try
y = 0
x = 10 / y
Catch ex As Exception When y = 0 ' Argument and When is optional
Console.WriteLine(ex.Message)
Finally
Beep()
End Try
' Deprecated unstructured error handling
On Error GoTo MyErrorHandler
...
MyErrorHandler: Console.WriteLine(Err.Description)
|
// Throw an exception
Exception up = new Exception("Something is really wrong.");
throw up; // ha ha // Catch an exception
try {
y = 0;
x = 10 / y;
}
catch (Exception ex) { // Argument is optional, no "When" keyword
Console.WriteLine(ex.Message);
}
finally {
// Requires reference to the Microsoft.VisualBasic.dll
// assembly (pre .NET Framework v2.0)
Microsoft.VisualBasic.Interaction.Beep();
} |
|
|
| Namespace Harding.Compsci.Graphics
...
End Namespace ' or Namespace Harding
Namespace Compsci
Namespace Graphics
...
End Namespace
End Namespace
End Namespace Imports Harding.Compsci.Graphics |
namespace Harding.Compsci.Graphics {
...
} // or namespace Harding {
namespace Compsci {
namespace Graphics {
...
}
}
} using Harding.Compsci.Graphics; |
|
|
| Accessibility keywords
Public
Private
Friend
Protected
Protected Friend
Shared ' Inheritance
Class FootballGame
Inherits Competition
...
End Class ' Interface definition
Interface IAlarmClock
...
End Interface // Extending an interface
Interface IAlarmClock
Inherits IClock
...
End Interface // Interface implementation
Class WristWatch
Implements IAlarmClock, ITimer
...
End Class |
Accessibility keywords
public
private
internal
protected
protected internal
static // Inheritance
class FootballGame : Competition {
...
}
// Interface definition
interface IAlarmClock {
...
}
// Extending an interface
interface IAlarmClock : IClock {
...
}
// Interface implementation
class WristWatch : IAlarmClock, ITimer {
...
}
|
|
|
Class SuperHero
Private _powerLevel As Integer
Public Sub New ()
_powerLevel = 0
End Sub
Public Sub New (ByVal powerLevel As Integer)
Me._powerLevel = powerLevel
End Sub
Protected Overrides Sub Finalize ()
' Desctructor code to free unmanaged resources
MyBase.Finalize()
End Sub
End Class |
class SuperHero {
private int _powerLevel;
public SuperHero() {
_powerLevel = 0;
}
public SuperHero(int powerLevel) {
this._powerLevel= powerLevel;
}
~ SuperHero() {
// Destructor code to free unmanaged resources.
// Implicitly creates a Finalize method
}
} |
|
|
| Dim hero As SuperHero = New SuperHero
' or
Dim hero As New SuperHero With hero
.Name = "SpamMan"
.PowerLevel = 3
End With
hero.Defend("Laura Jones")
hero.Rest() ' Calling Shared method
' or
SuperHero.Rest() Dim hero2 As SuperHero = hero ' Both reference the same object
hero2.Name = "WormWoman"
Console.WriteLine(hero.Name) ' Prints WormWoman hero = Nothing ' Free the object If hero Is Nothing Then _
hero = New SuperHero Dim obj As Object = New SuperHero
If TypeOf obj Is SuperHero Then _
Console.WriteLine("Is a SuperHero object.") ' Mark object for quick disposal
Using reader As StreamReader = File.OpenText("test.txt")
Dim line As String = reader.ReadLine()
While Not line Is Nothing
Console.WriteLine(line)
line = reader.ReadLine()
End While
End Using |
SuperHero hero = new SuperHero();
// No "With" construct
hero.Name = "SpamMan";
hero.PowerLevel = 3;
hero.Defend("Laura Jones");
SuperHero.Rest(); // Calling static method
SuperHero hero2 = hero; // Both reference the same object
hero2.Name = "WormWoman";
Console.WriteLine(hero.Name); // Prints WormWoman
hero = null ; // Free the object if (hero == null )
hero = new SuperHero(); Object obj = new SuperHero();
if (obj is SuperHero)
Console.WriteLine("Is a SuperHero object."); // Mark object for quick disposal
using (StreamReader reader = File.OpenText("test.txt")) {
string line;
while ((line = reader.ReadLine()) != null)
Console.WriteLine(line);
} |
|
|
| Structure StudentRecord
Public name As String
Public gpa As Single
Public Sub New(ByVal name As String, ByVal gpa As Single)
Me.name = name
Me.gpa = gpa
End Sub
End Structure Dim stu As StudentRecord = New StudentRecord("Bob", 3.5)
Dim stu2 As StudentRecord = stu
stu2.name = "Sue"
Console.WriteLine(stu.name) ' Prints Bob
Console.WriteLine(stu2.name) ' Prints Sue |
struct StudentRecord {
public string name;
public float gpa;
public StudentRecord(string name, float gpa) {
this.name = name;
this.gpa = gpa;
}
}
StudentRecord stu = new StudentRecord("Bob", 3.5f);
StudentRecord stu2 = stu;
stu2.name = "Sue";
Console.WriteLine(stu.name); // Prints Bob
Console.WriteLine(stu2.name); // Prints Sue |
|
|
| Private _size As Integer
Public Property Size() As Integer
Get
Return _size
End Get
Set (ByVal Value As Integer)
If Value < 0 Then
_size = 0
Else
_size = Value
End If
End Set
End Property foo.Size += 1 |
private int _size;
public int Size {
get {
return _size;
}
set {
if (value < 0)
_size = 0;
else
_size = value;
}
}
foo.Size++;
|
|
|
| Delegate Sub MsgArrivedEventHandler(ByVal message As String) Event MsgArrivedEvent As MsgArrivedEventHandler ' or to define an event which declares a delegate implicitly
Event MsgArrivedEvent(ByVal message As String) AddHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback
' Won't throw an exception if obj is Nothing
RaiseEvent MsgArrivedEvent("Test message")
RemoveHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback
Imports System.Windows.Forms Dim WithEvents MyButton As Button ' WithEvents can't be used on local variable
MyButton = New Button Private Sub MyButton_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyButton.Click
MessageBox.Show(Me, "Button was clicked", "Info", _
MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub |
delegate void MsgArrivedEventHandler(string message); event MsgArrivedEventHandler MsgArrivedEvent; // Delegates must be used with events in C#
MsgArrivedEvent += new MsgArrivedEventHandler(My_MsgArrivedEventCallback);
MsgArrivedEvent("Test message"); // Throws exception if obj is null
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);
} |
|
|
| Console.Write("What's your name? ")
Dim name As String = Console.ReadLine()
Console.Write("How old are you? ")
Dim age As Integer = Val(Console.ReadLine())
Console.WriteLine("{0} is {1} years old.", name, age)
' or
Console.WriteLine(name & " is " & age & " years old.")
Dim c As Integer
c = Console.Read() ' Read single char
Console.WriteLine(c) ' Prints 65 if user enters "A" |
Console.Write("What's your name? ");
string name = Console.ReadLine();
Console.Write("How old are you? ");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("{0} is {1} years old.", name, age);
// or
Console.WriteLine(name + " is " + age + " years old.");
int c = Console.Read(); // Read single char
Console.WriteLine(c); // Prints 65 if user enters "A"
|
|
|
| Imports System.IO ' Write out to text file
Dim writer As StreamWriter = File.CreateText("c:\myfile.txt")
writer.WriteLine("Out to file.")
writer.Close() ' Read all lines from text file
Dim reader As StreamReader = File.OpenText("c:\myfile.txt")
Dim line As String = reader.ReadLine()
While Not line Is Nothing
Console.WriteLine(line)
line = reader.ReadLine()
End While
reader.Close() ' Write out to binary file
Dim str As String = "Text data"
Dim num As Integer = 123
Dim binWriter As New BinaryWriter (File.OpenWrite("c:\myfile.dat"))
binWriter.Write(str)
binWriter.Write(num)
binWriter.Close()
' Read from binary file
Dim binReader As New BinaryReader (File.OpenRead("c:\myfile.dat"))
str = binReader.ReadString()
num = binReader.ReadInt32()
binReader.Close() |
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 |
