Friday, October 07, 2005

Linq and DLinq in action

Beta version of Visual C# 2005 Express Edition was lying around my hard disk for some times. I was stuck with a project and didn't have chance to look into it. When I visited LINQ site, I found the way to use it. I've downloaded Tech Preview version of LINQ and installed it. Integration with Visual C# 2005 was not so hard and I was already in new Linq consol application window. I found couple of doc files on 'Hands on Lab' inside 'Docs' folder. After reading a file for DLinq, I got general idea on how actually LINQ works. In order to start with DLinq, I first made a ObjectModel of 'Pubs' database using a tool 'sqlmetal.exe'. This tool is installed in Bin folder and able to create a C# source file which contains mapping of every table and column to respective objects. The resulting source was then included in Linq console application. With little modification in ObjectModel, I was able to use SqlConnection object with my 'pubs' class. By writing a code (as shown below), I was able to see the result of database immediately. The bottom line is, with LINQ, there is no need to write SQL. The query language is now integrated in programming language. I think it is easy to use and developer doesn't need to have knowledge of SQL. Till now, I have learnt to get the result from database. Now my target is to learn how to insert, update and delete records using LINQ.

using System;
using System.Collections .Generic;
using System.Text;
using System.Query;
using System.Xml.XLinq;
using System.Data.DLinq;
using System.Data.SqlClient;
using pubs;

namespace LINQApp
    class Program
        static void Main(string[] args)

        static void dbQuery()
            SqlConnection conn = 
                     new SqlConnection(@"SERVER={YourDBServer};user id={uid};password=;database=pubs;");
            Pubs db = new Pubs(conn);

             var authors = 
                 from  a in db.Authors
                 select a;

            foreach (var auth in authors)
                Console.WriteLine(" {0} {1} | {2} | {3} ", 
                                       auth.AuFname, auth.AuLname, auth.Address, auth.Phone);

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