Dr. Dobb's Journal - December 2008 - (Page 30)

d12espo_p5db 10/16/08 7:25 AM Page 30 Core Technology LINQ-TO-SQL AND T-SQL writing, maintaining, and fine-tuning stored procedures and indexes? Is LINQ-toSQL a tool that diminishes the role of handcrafted T-SQL code? Are T-SQL skills a thing of the past? Should we just take the T-SQL code that LINQ-to-SQL generates underthe-hood without any possibility of intervention? LINQ-to-SQL is not here to kill T-SQL and related skills; LINQ-to-SQL is here to help. But it is a tool that heralds upcoming radical changes in the development of multitier systems. The more we move towards an object-oriented design of the business logic, the more we need powerful tools to smooth the subsequent object/relational impedance mismatch. LINQ-to-SQL may not be the perfect tool for the purpose, but its introduction should be seen in this perspective. The real question is whether you’re okay with a table-based representation of data. Are you fine working with recordset-like data structures? Is it okay for you to implement CRUD and query services with a mix of stored procedures and ADO.NET-based PC Presents Bug of the Month #583 business components? If the answer is “yes,” then you probably don’t need LINQto-SQL. But if your answer to the previous question is “No, I would really like to employ objects to represent my problem’s domain,” then LINQ-to-SQL is the first step in a new direction. LINQ-to-SQL uses T-SQL underthe-hood, but leaves room for customization. As a SQL Server expert, you should be looking at LINQ-to-SQL internals to see where you can intervene to improve things. LINQ-to-SQL may become your best friend and a higher level tool to work with. -lint 9.0 for C/C++ #include const int NC = 2; extern char Cairo[], Tokyo[]; char *Cities[NC] = { Cairo, Tokyo }; FILE *f[NC]; int main() { char ch; int i; for( i = 0; i < NC; i++ ) { f[i] = fopen(Cities[i],"wb"); if( !f[i] ) return 0; } while( (ch = getchar()) != EOF ) { for( i = 0; i < NC; i++ ) putc( ch, f[i] ); } return 0; } The Object Model LINQ-to-SQL is all about its object model. Through the object model you define the model of data you’ll work with. The object model contains classes that may contain both data and behavior—persistence, logic, and validation. The Visual Studio 2008 wizard is the easiest starting point for building such an object model. However, it is ultimately a collection of classes that can be written manually. Suppose you intend to connect to the standard Northwind database and work with Customers and Orders tables. You end up with a Customer class as in Listing One. The LINQ-to-SQL object model is essentially a table-centric object model with a varying level of abstraction. In the default source code for the various classes, the abstraction over the physical structure of the tables is null. As you can see in Listing One, Customer is a faithful representation of a record in the Customers table. However, the class is decorated with a few attributes and is marked as partial. The class is a plain class that just exposes a few properties and implements a few interfaces. More precisely, it is a plain class that operates as a table record class. Properties and the class itself are mapped to columns of a particular table through attributes. Attributes contain metadata that bind a particular property to a particular column and the whole class to a table record. The attribute contains information about name and type of the column, plus additional information such as primary key, nullability, and constraints: WN NE SIO R VE In order to help Santa, the elves decided to teleport toys throughout the world. A recording of some gift is passed as standard input to this program and sent to two test cities. Why did Cairo receive only half a bicycle? Visit our web site at www.gimpel.com PC-lint for C/C++ will catch this and many other bugs. It will analyze a mixed suite of C and C++ modules to uncover bugs, glitches, quirks and inconsistencies. Introducing Version 9.0: What, you ask, can be added to our ground-breaking lint products -products that already contain interfunction value tracking, auto variable and member value tracking, customizable function semantics, a comprehensive system of message suppression, and a rich set of over 500 Warnings that all together provide an environment in which few bugs can survive and none can flourish? The answer to that question is found in Version 9.0, which provides support for pre-compiled headers, static variable tracking, muti-thread analysis, support for MISRA C 2004 and MISRA C++ 2008, a rich set of program information reports including stack usage, and over 146 new messages. Full Support for ANSI/ISO C and C++. PC-lint for C/C++ Numerous compilers/libraries supported. Runs on Windows, MSDOS, and OS/2. $389 Call FlexeLint for C/C++ 30 Day Money Back Guarantee The same great product for all UNIX systems. Distributed in shrouded C source form. Gimpel Software Serving the C/C++ Community for 22 Years. CALL TODAY (610) 584-4261 Or FAX (610) 584-4266 www.gimpel.com PC-lint and FlexeLint are trademarks of Gimpel Software 30 Dr. Dobb’s Journal l www.ddj.com l December 2008 http://www.gimpel.com http://www.gimpel.com http://www.gimpel.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - December 2008

Dr. Dobb's Journal - December 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Conversations The Man Who Sold the Sky Performance on Rails LINQ-to-SQL and T-SQL A Remote Java RMI Registry Beyond B-Trees File Descriptors and Multithreaded Programs Effective Concurrency The Agile Edge Swaine's Flames

Dr. Dobb's Journal - December 2008

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