A brief introduction to Csharp

A Brief Introduction to C#
David Buksbaum

Agenda
•
Goals
•
Background Information
•
C# - Up and Running
•
Quick Comparison to Java
•
Networking Namespaces
•
References

Goals
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Provide enough information to allow you to
follow the code samples
•
Highlight key differences with Java
•
Tell you where you can get the compilers
•
Tell you where to go for more details on C#
•
Tell you where to go for more detailed
comparisons with Java

•
Not to debate which is better, more important,
faster, slower, or looks better in emacs

Quick Glossary
•
BCL – Base Class Library
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CLR – Common Language Runtime
•
GUI – Graphic User Interface
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MSIL – Microsoft Intermediate Language
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MS – Microsoft
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SCM – Service Control Manager
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SOA – Service Oriented Architecture

.NET
•
.NET is:
•
Microsoft’s Platform for Windows Development
•
CLR – the Virtual Machine that runs MSIL aka MS
Byte Code
•
BCL aka .NET Framework

•
A set of compilers that can generate MSIL C#,
Visual Basic, C++, Java (the MS flavor)
•
There are 50+ languages that generate MSIL
•
/>•
Most interoperate with each other

C#
•
Language Created by Anders Hejlsberg (father of
Delphi)
•
The Derivation History can be viewed here:
/>•
Principle Influencing Languages:
•
C++
•
Delphi
•
Java
•
Designed to be an optimal Windows development
language

C# - Up and Running
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A Simple C# Application

•
Application Types
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Compiler & Run Time

A Sample C# Application

Application Types
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Console Application
•
Has standard streams (out, in, err)
•
GUI can be added manually
•
Windows Application
•
GUI based
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No standard streams (out, in, err)
•
Main thread is shared by the GUI message pump & your
code
•
Service
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No standard streams (out, in, err)
•
Main thread is commandeered by the SCM
•

No GUI

Compiler Options from MS
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SDK contains the command line compiler
(C:\WINDOWS\Microsoft.NET\Framework\
{version}\csc.exe)
•
{version} looks like v2.0.50727
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Express Edition – Free IDE to work with Visual
C#
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Reduced runctionality version of Visual Studio
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Visual Studio – The full development system
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Optimizations, Data Access, Multi-Language, etc
•
$$$

Options Beyond MS
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Mono
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Open source development SDK for .NET
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Windows, Linux, Mac OS X, Solaris, Unix
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Sponsored by Novell

•
Food for thought: Suse + KDE + Mono = ???
•
Sharp Develop
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Open source IDE that uses .NET SDK or Mono
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Written in C#

Quick Comparison to Java
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What’s the same
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Syntactically Similar
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Garbage Collected VM Environment
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Immutable Strings
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Exceptions (try / catch / finally)
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Object as root
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Single Inheritance model
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Multi-Interface model

What’s Different & Relevant
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Keywords

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base vs. super
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lock vs. synchronized
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: vs. extends & implements
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is vs. instanceof
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Exceptions
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No throws keyword
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See
/>032103.aspx

What’s Different & Relevant – cont.
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Namespaces
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namespace vs. package
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using vs. import
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No wildcard using
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using namespace; // brings it all in – non-recursive
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Type Aliasing
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using newtypename = namespace.type;
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Directory structure != namespace hierarchy (as in
C++)

What’s Different & Relevant – cont.
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Properties
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get, set and get/set
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public string MyProperty { get { return(_text); } set { _text =
value; } }
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Delegates
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Type safe function pointers
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To create
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public delegate bool CompareHandler(object left, object
right);
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To use
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CompareHandler ch = new CompareHandler(myMethod);
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bool retval = ch(obj1, obj2);

What’s Different & Relevant – cont.

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Enumerations
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public enum Protocol { UDP, TCP };
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public enum Direction { Up = 0, Down = 1, Left = 2,
Right = 4 };
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Direction d = Direction.Down;
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int x = (int)d;
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Direction d = Direction.Parse(“Up”);
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string s = d.ToString();

What’s Different & Relevant – cont.
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Value Types
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Primitives are the same plus
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Unsigned values
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ubyte, ushort, uint, ulong
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Careful: byte in java is sbyte in C#
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Class objects to wrap primitives
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Int32 x = new Int32(4);
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int x = Int32.Parse(“4”);

What’s Different & Relevant – cont.
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Structures
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Stack based elements, not heap based
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Value type
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struct packet { int code; string data; };
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Boxing / Unboxing
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Conversion between value type and reference type
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packet p = new packet();
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object o = (object)p; // boxed
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packet p2 = (packet)o; // unboxed
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Significant performance cost!

What’s Different & Relevant – cont.
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Cross Platform Support
•

.NET from Microsoft is not cross platform
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It is for Windows only
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Mono can run cross platform, but is unproven in
large production environments
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MS is currently resisting moving cross platform
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The future is not set

What’s not Relevant, but Useful
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App Domains
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One or more per process
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Represents a VM hosted logical process
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Communications between App Domains requires
marshalling (IPC)
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Assemblies
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Similar to Java JAR files
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Physically they are EXE and/or DLL files

What’s not Relevant, but Useful
•

Attributes
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Meta tags that provide run time information for a
type, NOT the instance
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Example: [Serializable] public class foo { int x; };
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[Serializable] is converted into the class
SerializableAttribute
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Attributes can be retrieved at run time
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Many framework sub-systems use attributes
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Serialization, XML, Interop, Conditional, Obsolete, etc…

What’s not Relevant, but Useful
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Polymorphism
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Methods default to being non-virtual
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To be virtual it must be defined as virtual
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eg: public virtual int Add(int x, int y);
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To override a virtual method, you use the override
keyword
•
eg. public override int Add(int x, int y);

•
Methods not marked virtual are equivalent to Java
final methods
•
Methods can be marked with new to break the
virtual chain

What’s not Relevant, but Useful
•
Interop
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Access to native code through attributes
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[DllImport(“user32.dll”)] static int
GetSystemMetrics(int);
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The DllImport attribute informs the compiler and
runtime that the tagged method is inside a native
DLL.
•
Options such as the actual name in the DLL,
marshalling strategies, calling convention, and more
can be set using the attribute

What’s not Relevant, but Useful
•
.NET 2.0 – out now
•
Generics
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Partial Types
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Anonymous Methods
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Nullable Types
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.Net 3.0
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Its all about data
•
Tuples & Query constructs
public void Linq1()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var lowNums = from n in numbers where n < 5 select n;
Console.WriteLine("Numbers < 5:");
foreach (var x in lowNums) { Console.WriteLine(x); }
}
Result
Numbers < 5:
4
1
3
2
0

Networking Namespaces
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System.Messaging
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Functionality for MSMQ
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System.Net
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Provides access to higher protocols (FTP, HTTP, DNS)
•
System.Net.Information
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Network information classes providing statistics, interface
information, and ping
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System.Net.Sockets
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Light weight wrappers around TCP and UDP sockets
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System.Runtime.Remoting
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Provides functionality for high level distributed programming
(similar to RMI)
•
System.Web
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Provides high level access to HTTP