The .NET Framework

1. The .NET Framework • What is Microsoft .NET? • A programming model: CLR + Classes • XML Web services • Server and Client software and tools

2. Common Language Runtime (CLR) • It’s a VM (Java-like) on which any (supported) language can run. • Why a VM? • Memory Protection • Cross-language • Support for strong-typing across languages (the data are typed) • Thread support • JIT compilation in the VM

3. Languages in CLR • Language of choice is C# (“C-sharp”) a Java-like language • No inner classes • Better type checking • Other languages will run on CLR, but only within the CLR constraints • Visual Basic, JScript are full fledged CLR languages • For example, only C++ that is VM-safe will run • That subset looks much like C# • Under CLR, all languages get object features • Inheritance used extensively • Every language gets constructors

4. Languages compile to MSIL • Languages compile to MSIL (Microsoft Intermediate Language) • Can you say “bytecodes”? • MSIL is shipped in portable executable (PE) units • Can you say .class files or applets? • An application is made up of assemblies

5. Assemblies • In general, a static assembly can consist of four elements: • The assembly manifest, which contains assembly metadata. • Type metadata. • Microsoft intermediate language (MSIL) code that implements the types. • A set of resources.

6. Assemblies can be spread across .NET

7. Assemblies are the security unit • Each assembly has a set of corresponding grants • Each grant allows certain permissions • DnsPermission, Environment, FileDialog, FileIO, IsolatedStorage, Reflection, Registry, Security, UI, WebPermission, SocketPermission • The set of grants establishes a security policy

8. Class Library • Data classes support persistent data management and include SQL classes. • XML classes enable XML data manipulation and XML searching and translations. • Windows Forms support development of Windows GUI applications across CLR • Web Forms include classes that enable you to rapidly develop web GUI applications.

9. System.Object • Public methods: • Equals • GetHashCode • GetType • ToString • Overriding inherited behaviors is common

10. Web, Windows, Whatever • Part of the idea is to smooth transitions between Windows and Web • Web interfaces become easier for Windows developers • Windows apps become .NET Web-based apps

11. Data <-> XML, Everywhere • All CLR data can be serialized to XML • All XML can be expanded into CLR data • Thus, anything can be shipped around on the Web • Typing through XML Schema

12. XML Schema <xsd:complexType name="Person"> <xsd:sequence> <xsd:choice> <xsd:element name="name" type="xsd:string" xsi:nillable="true" /> <xsd:element name="id" type="xsd:string" /> </xsd:choice> <xsd:any processContents="lax"/> </xsd:sequence> </xsd:complexType> <xsd:complexType name="AgedPerson"> <xsd:complexContent mixed="false"> <xsd:extension base="target:Person"> <xsd:choice> <xsd:element name="age" type="xsd:double" /> <xsd:element name="timeOnEarth" type="xsd:double" /> </xsd:choice> </xsd:extension> </xsd:complexContent> </xsd:complexType> <xsd:element name="don" type="target:Person" />

13. Example Instance <ns:don xmlns:ns="uuid:048b2fa1-d557-473f-ba4c- acee78fe3f7d" > <name>Don Box</name> <niceStuffForDon/> </ns:don>

14. Second Example Instance <ns:don xmlns:ns="uuid:048b2fa1-d557-473f-ba4c-acee78fe3f7d" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns:AgedPerson" > <name>Don Box</name> <niceStuffForDon/> <age>26</age> </ns:don>

15. A Simpler Schema <element name="Book"> <complexType> <element name="author" type="xsd:string"/> <element name="preface" type="xsd:string"/> <element name="intro" type="xsd:string"/> </complexType> </e:Book>

16. Another Example Instance <e:Book> <author>Henry Ford</author> <preface>Prefatory text</preface> <intro>This is a book.</intro> </e:Book>

17. XML Schema Defined Types

18. Class Library Data Hierarchy

19. Reading in XML Data XmlReader reader = new XmlTextReader("http://foo.com/don.xsd"); XmlSchema schema = XmlSchema.Load(reader, null); schema.Compile(null); // turn xml into objects reader.Close();

20. ALL Interprocess Communication via SOAP • ALL Interprocess communication (across network or on same machine) is through SOAP • Simple Object Access Protocol • It’s a way of exchanging data and even calling other methods/threads, all via XML and plain old HTTP requests

21. Example SOAP Request POST /StockQuote HTTP/1.1 Host: www.stockquoteserver.com Content-Type: text/xml; charset="utf-8" Content-Length: nnnn SOAPAction: "Some-URI" <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"> <SOAP-ENV:Body> <m:GetLastTradePrice xmlns:m="Some-URI"> <symbol>DIS</symbol> </m:GetLastTradePrice> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

22. Example SOAP Response HTTP/1.1 200 OK Content-Type: text/xml; charset="utf-8" Content-Length: nnnn <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/> <SOAP-ENV:Body> <m:GetLastTradePriceResponse xmlns:m="Some-URI"> <Price>34.5</Price> </m:GetLastTradePriceResponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

23. ASP.NET • ASP => Active Server Pages • Put most of the computation in the server • Very simple model to use • ADO.NET is the database connection part

24. Calling Web Services • Any class can be converted into an XML Web Service with just a few lines of code, and can be called by any SOAP client. 

25. Take-away lessons • VM’s are important • Even Microsoft thinks so • Distributed apps are important, but to do so requires standard protocols • Ways of serializing data • Ways of doing RPC

26. Limitations of the .NET Framework • What if you’re not on the network? • Maybe that’s not an issue? • Mapping between XML and any object is hard • Any object is controlled by compiler. XML can be written by anybody with a text editor. • There’s a whole bunch of class support for modified serializers and compilers