Lecture introduction to Csharp

Introduction to C#
Tom Roeder
CS 215 2006fa

Goals of the course

Introduce C# language

ECMA standard

originally developed by MSR

not just Java + C++

many extensions

Introduce .NET framework

future of Windows

base of Microsoft’s C# implementation

Non-goals

Teach you to program

should be very comfortable writing OO code

we will not cover much if any basic programming


Introduce object oriented
languages

not even teach you OO style (except wrt C#)

expected to write all code in OO style

Give you a detailed grade

S/U only

even homework

S/U Details

Requirements for the course

come to lecture

participate

do three assignments

Assignments are S/U

will not be giving a detailed grade

show me that you understand the concepts, and can write C#
code


All three assignments will be online
soon

must be completed by the end of the course

Administrative Details

Class time MWF 12:20-1:10

office hours: W 10:30-12 or by
appointment

(4112 Upson)

Prerequisites: CS 211/212

really: experience in OO coding/concepts

Academic Integrity

Do not submit work that is not your own

minimum penalty: U in the course

Useful Tools

Visual C#

Express: Google “Visual C# Express”


in Visual Studio: MSDNAA

must be version 2005: we need C# 2.0

Mono:

Open Source impl for Linux: not quite at 2.0

Rotor:


Shared Source impl for Windows (through 2.0)

Used to work on BSD / OS X, too

Useful Tools

Portable.NET:

yet another open source impl

CMS:

we will use this for homework

turn on your email notifications!

Course Webpage: http
://www.cs.cornell.edu/courses/cs215


will post lectures online

as well as any errata for the homework

CSUGLab

You all will have accounts

MSDNAA access: let me know if you don’t
currently have it

/>
Visual Studio .NET 2005 should be installed there

Syllabus

Syllabus (10 more lectures)

C# constructs: 5 lectures

Types, Delegates, Generics, Reflection, Iterators

.NET Memory Management: 1 lecture

Topics: 4 lectures

C# 3.0, Threading, Security, MSIL, MSH

Quiz 1


Each class will begin with a quiz

not for credit but for knowledge

but I will collect them and see what you know

Today’s quiz will be on
prerequisites

OO programming, mainly to do with Java

If you don’t know Java, but do have OO
experience, it’s OK

talk to me after if you have trouble

What is .NET?

A Framework in which to run code

A Common Language Runtime (CLR)

runs all programs

C# compiles to Microsoft Intermediate Language

MSIL runs on CLR

Virtual Machine like Java


code written in many languages compiles to MSIL

A Common Language Specification
(CLS)

A Common Type System (CTS)

What is .NET?
Runtime
Operating System
.NET Framework
Common
Type
System
Common
Language
Runtime
Building Blocks (e.g. for Services)
Services: .NET and COM+
SQL Server BizTalk
Languages:
C#, Visual Basic, etc
.NET Applications
Enterprise Servers

Sharepoint
Web Services
From MSDN

What is the CLR?

Class Loader
MSIL to Native
Compilers (JIT)
Code
Manager
Garbage
Collector (GC)
Security Engine Debug Engine
Type Checker Exception Manager
Thread Support COM Marshaler
Base Class Library Support
From MSDN

What is the CTS?

A set of common types

any language that runs in CLR should implement

no syntax specified

Languages often define aliases

For example

CTS defines System.Int32 – 4 byte integer

C# defines int as an alias of System.Int32

What is the CTS?

From MSDN

What is the CLS?

A specification of language
features

how methods may be called

when constructors are called

subset of the types in CTS are allowed

For example

Code that takes UInt32 in a public method

UInt32 is not in the CLS

Can mark classes as CLS-compliant

not marked is assumed to mean not compliant

The Class Libraries

The common classes used in many
programs

like Java Class Library


eg.

System.Console.WriteLine

XML, Networking, Filesystem, Crypto, containers

Can inherit from many of these classes

Many languages run on .NET framework

C#, C++, J#, Visual Basic

even have Python (see IronPython)

Assemblies

Code contained in files called
“assemblies”

code and metadata

.dll as before

to run: public static void Main(string[] args)

types

private: local directory, not accessible by others

eg. Wolfram .NETLink


shared: well-known location, can be GAC

strong names: use crypto for signatures

then can add some versioning and trust

COM vs .NET

Historically, COM provided this
integration

support for interfaces and interaction

given a GUID, lookup the type library

dynamically instantiate class

do RPC to make calls in many cases

Difficult to get right

software engineering problems

not type safe at all

ASP.NET and ADO.NET

Use .NET languages in web pages


thus can write typesafe code

server-side or client-side

Sharepoint interactions

can log in

Use the CLR to access databases

in the manner of ODBC

provides classes for access

Windows PowerShell

New shell originally for MS Vista

available for WinXP/2k3

native .NET

instantiates arbitary .NET classes and accesses them

Also can access COM objects

Allows better interaction with
programs

Can it surpass bash and others?

First C# Program
using System;
namespace Test {
int a = 137;
class Hello {
public static void Main(string[] args) {
Console.WriteLine(“Hello {0}”, a);
}
}
}

Constructions of Note

using

like import in Java: bring in namespaces

namespace

disambiguation of names

like Internet hierarchical names and Java naming

class

like in Java

single inheritance up to object

Constructions of Note

Console.Write(Line)

Takes a formatted string: “Composite Format”

Indexed elements: e.g., {0}

can be used multiple times

only evaluated once

{index [,alignment][:formatting]}

also can use as in Java

“Test “ + a

More C# : basic inheritance
class A {
protected int a;
public virtual void print() {
Console.WriteLine(“a = “ + a);
}
}
class B : A {
public override void print() {
Console.WriteLine(“a really = “ + (a + 137));
}
}