Introduction to C#

1. Introduction to C# Tom Roeder CS 215 2006fa

2. 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

3. 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

4. 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

5. Administrative Details • Class time MWF 12:20-1:10 • office hours: W 10:30-12 or by appointment • tmroeder@cs.cornell.edu (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

6. Useful Tools • Visual C# • Express: Google “Visual C# Express” • in Visual Studio: MSDNAA • must be version 2005: we need C# 2.0 • Mono: http://www.go-mono.com • Open Source impl for Linux: not quite at 2.0 • Rotor: http://msdn.microsoft.com/net/sscli • Shared Source impl for Windows (through 2.0) • Used to work on BSD / OS X, too

7. Useful Tools • Portable.NET: http://www.dotgnu.org • yet another open source impl • CMS: http://cms.csuglab.cornell.edu • 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

8. CSUGLab • You all will have accounts • MSDNAA access: let me know if you don’t currently have it • http://www.csuglab.cornell.edu/userinfo.html • Visual Studio .NET 2005 should be installed there

9. 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

10. 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

11. 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)

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

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

14. 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

15. What is the CTS? From MSDN

16. 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

17. 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)

18. 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

19. 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

20. 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

21. 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?

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

23. 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

24. 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

25. 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)); } }