1	C# Programming Language Overview Jim Fawcett CSE681 – SW Modeling & Analysis Summer 2003
2	C# Language Looks a lot like Java. A strong analogy between: Java Virtual Machine & .Net CLR Java bytecodes & .Net Intermediate Language Java packages & CRL components and assemblies Both have Just In Time (JIT) compilers Both support reflection, used to obtain class information at run time Both languages lack generics Differences: Java and C# do have significant differences C# has most of the operators and keywords of C++ C# has enumerations C# plans to add generics in the second release of Visual Studio 7 C# code supports attributes – tagged metadata
3	First C# Program
4	Differences Between C# and C++ In C# there are no global functions. Everything is a class. Main(string args[]) is a static member function of a class. The C# class libraries are like Java Packages, not like the C and C++ Standard Libraries. System, System.Drawing, System.Runtime.Remoting, System.Text, System.Web C# class hierarchy is rooted in a single “Object” class C# does not separate class declaration and member function definitions. Every function definition is inline in the class declaration – like the Java structure. There are no header files. Instead of #include, C# uses using statements: using System; using System.ComponentModel;
5	Differences between C++ and C# The C# object model is very different from the C++ object model. Illustrated on the next slide C# supports only single inheritence of implementation, but multiple inheritance of interfaces C# does not support use of pointers, only references, except in “unsafe” code. Use of a C# variable before initialization is a compile-time error.
6	C# Object Model
7	More Differences The CLR defines a new delegate type, used for callbacks. event is a keyword in all CLR languages. All memory allocations are subject to garbage collection – you don’t call delete. There are no #includes unless you want to use unmanaged C++ in the same file as managed C++. In managed C++ all class data members are either primitive value types, C++ references, or C++ pointers. Nothing else is allowed. The CLR provides threads, directory services, and remoting. The Standard C++ Library provides non of these, although the first two are easy to provide yourself.
8	Common Type System Value Types Primitive types See page 10 Structures methods fields properties Events Member adornments: public, protected, private, abstract, static Enumerations
9	Common Type System Reference Types Classes methods fields properties Events Member adornments: public, protected, private, abstract, static Interfaces Class can inherit more than one Must implement each base interface Delegates Instances used for notifications
10	C# Primitive Types .Net Base Class System.Byte System.SByte System.Int16 System.Int32 System.Int64 System.UInt16 System.UInt32 System.UInt64 System.Single System.Double System.Object System.Char System.String System.Decimal System.Boolean C# Types byte sbyte short int long ushort uint ulong float double object char string decimal bool
11	C# Object Type Object is the root class of the C# library Object’s members: public Object(); public virtual Boolean Equals(Object obj); Returns true if obj and invoker handles point to the same body. public virtual Int32 GetHashCode(); Return value identifies object instance. public Type GetType(); Type object supports RTTI – see next page public virtual String ToString(); Returns namespace.name protected virtual void Finalize(); Called to free allocated resources before object is garbage collected. protected Object MemberwiseClone(); Performs shallow copy To have your class instances perform deep copies you need to implement the ICloneable interface.
12	Type Class You get a type object in several ways: Type t = myObj.GetType(); Type t = Type.GetType(“myObj”); Some of Type’s members: IsAbstract IsArray IsClass IsComObject IsEnum IsInterface IsPrimitive IsSealed IsValueType InvokeMember() GetType() returns Type Object FindMembers() returns MemberInfo array GetEvents() returns EventInfo array GetFields() : GetMethods() : GetInterfaces() : GetMembers() : GetProperties() :
13	"You get type object this..." You get type object this way: Type t = myObj.GetType(); Type t = Type.GetType(“myObj”); Some of Type’s members: IsAbstract IsArray IsClass IsComObject IsEnum IsInterface IsPrimitive IsSealed IsValueType InvokeMember() GetType() returns Type Object FindMembers() returns MemberInfo array GetEvents() returns EventInfo array GetFields() : GetMethods() : GetInterfaces() : GetMembers() : GetProperties() :
14	WinCV – Class Viewer
15	System.string Class – view #1
16	Class Browser in IDE
17	Useful Interfaces IComparable - method Int CompareTo(object obj); Return: Negative => less Zero => equal Positive => greater ICloneable - method object clone(); ICollection – properties and method int count { get; } bool IsSynchronized { get; } object SyncRoot { get; } void CopyTo(Array array, int index);
18	Useful Interfaces IEnumerable - method System.Collections.IEnumerator GetEnumerator(); IEnumerator – property and methods object Current { get; } bool MoveNext(); void Reset();
19	Useful Interfaces IDictionary bool IsFixedSize { get; } bool IsReadOnly { get; } object this[ object key ] { get; set; } ICollection keys { get; } ICollection values { get; } void Add(object key, object value); void Clear(); bool Contains(object key); System.Collections.IDictionaryEnumerator GetEnumerator(); void Remove(object key); IList bool IsFixedSize { get; } bool IsReadOnly { get; } object this[ object key ] { get; set; } void Add(object key, object value); void Clear(); bool Contains(object key); int IndexOf(object value); void Insert(int index, object value); void Remove(object value); void RemoveAt(int index);
20	Delegates Delegates are used for callbacks: In response to some event they invoke one or more functions supplied to them. Library code that generates an event will define a delegate for application developers to use – the developer defines application specific processing that needs to occur in response to an event generated by the library code. A delegate defines one specific function signature to use: public delegate rtnType delFun(args…); This declares a new type, delFun that invokes functions with that signature. The developer supplies functions this way: libClass.delFun myDel = new libClass.delFun(myFun); This declares a new instance, myDel, of the delFun type.
21	Events Events are specialized delegates that are declared and invoked by a class that wants to publish notifications. The event handlers are functions created by an event subscriber and given to the delegate. A C# event uses the specialized delegate event handler of the form: public delegate void evDelegate( object sender, userEventArgs eArgs ); userEventArgs is a subscriber defined class, derived from System.EventArgs. You usually provide it with a constructor to allow you to specify information for the event to use. The event is then declared by the publisher as: public event evDelegate evt; Either publisher or subscriber has to create a delegate object, eveDel, and pass it to the other participant. The event is invoked by the publisher this way: evDel( this, new userEventArgs(arg) ); The subscriber adds an event handler function, myOnEvent, to the event delegate this way: Publisher.evDelegate evDel += new Publisher.evDelegate(myOnEvent);
22	Threads A C# thread is created with the statement: Thread thrd = new Thread(); System.Threading declares a delegate, named ThreadStart, used to define the thread’s processing. ThreadStart accepts functions that take no arguments and have void return type. You define a processing class that uses constructor arguments or member functions to supply whatever parameters the thread processing needs. To start the thread you simply do this: Thread thrd = new Thread(); ThreadStart thrdProc = new ThreadStart(myProc); thrd.Start(thrdProc);
23	Thread Synchronization The simplest way to provide mutually exclusive access to an object shared between threads is to use lock: lock(someObject) { // do some processing on // someObject } While a thread is processing the code inside the lock statement no other thread is allowed to access someObject.
24	Components Because C# classes are reference types, they expose no physical implementation detail to a client. What the client creates on its stack frames are simply handles to the class implementations. The compiler does type checking for a client from metadata in an accessed assembly. No header file is included, so the client is not dependent on implementation details of the class. Consequently, any C# library dll can serve as a component for local access. To make a component remotely accessible, you need to derive from System.MarshalByRefObject
25	C# Object Model
26	Assemblies An assembly is a versioned, self-describing binary (dll or exe) An assembly is the unit of deployment in .Net An assembly is one or more files that contain: A Manifest Documents each file in the assembly Establishes the assembly version Documents external assemblies referenced Type metadata Describes all the methods, properties, fields, and events in each module in the assembly MSIL code Platform independent intermediate code JIT transforms IL into platform specific code Optional resources Bitmaps, string resources, …
27	Assembly Structure Visual Studio does most of the work in configuring an assembly for you.
28	Metadata in demoFiles.exe
29	Versioning Assemblies can be public or private: A private assembly is used only by one executable, and no version information is checked at loadtime. Private assemblies are contained in the project directory or, if there is a config file, in a subdirectory of the project directory. A shared assembly is used by more than one executable, and is loaded only if the version number is compatible with the using executable. Shared assemblies reside in the Global Assembly Cache (GAC), a specific directory. Version compatibility rules can be configured by the user. Since no registry entries are made for the assembly, each user executable can attach to its own version of the assembly. This is called side-by-side execution by Microsoft. A shared assembly is created from a private assembly, using one of Microsoft’s utilities provided for that purpose.
30	C# Libraries System System.Collections ArrayList, Queue, Stack System.Collections.Specialized StringDictionary System.ComponentModel Used to create components and controls Used by WinForms System.ComponentModel.Design.Serialization Used to make state of an object persistant System.Data Encapsulates use of ADO.NET
31	More C# Libraries System.Drawing – GDI+ support System.Drawing.Drawing2D – special effects System.Drawing.Imaging – support for .jpg, .gif files System.Drawing.Printing – settings like margins, resolution System.Net – support for HTTP, DNS, basic sockets System.Net.sockets – sockets details System.Reflection view application’s meta data including RTTI System.Runtime.InteropServices Access COM objects and Win32 API
32	Remoting Libraries System.Runtime.Remoting System.Runtime.Remoting.Activation Activate remote objects System.Runtime.Remoting.Channels Sets up channel sinks and sources for remote objects System.Runtime.Remoting.Channels.HTTP Uses SOAP protocol to communicate with remote objects System.Runtime.Remoting.Channels.TCP Uses binary transmission over sockets System.Runtime.Remoting.Contexts Set threading and security contexts for remoting System.Runtime.Remoting.Messaging Classes to handle message passing through message sinks System.Runtime.Remoting.Meta data Customize HTTP SoapAction type output and XML Namespace URL System.Runtime.Remoting.Proxies System.Runtime.Remoting.Services
33	You must be joking – More Libraries! System.Runtime.Serialization System.Runtime.Serialization.Formatters System.Runtime.Serialization.Formatters.Soap System.Security System.ServiceProcess Create windows services that run as Daemons System.Text.RegularExpressions System.Threading Defines Mutex, Thread, and Timeout System.Timers Fire events at timed intervals, day, week, or month
34	Web Libraries System.Web System.Web.Hosting Communicate with IIS and ISAPI run-time System.Web.Mail System.Web.Security cookies, web authentication, Passport System.Web.Services – close ties to ASP.NET System.Web.Services.Description System.Web.Services.Discovery System.Web.Services.Protocol – raw HTTP and SOAP requests System.Web.SessionState – maintain state between page requests System.Web.UI – access to WebForms
35	WinForms and XML Libraries System.Windows.Forms – Forms based GUI design System.Xml – XML DOM System.Xml.Schema Authenticate XML structure System.Xml.Serialization Serialize to XML System.Xml.XPath Navigate XSL System.Xml.Xsl Support for XSL – XML stylesheets
36	So How do we Learn all this stuff! ClassView -> Class Browser -> Help to the rescue!
37	Access Class Browser from class View
38	Select Type to see its Members
39	Browsing System.DLL
40	Getting Help on a Selected Type or Member – Just hit F1
41	Takes you Immediately to Help Documentation for that Identifier