LINQ is Language Integrated query. It is a integral part of visual studio 2008 and Microsoft .NET Framework 3.5. It is object to database mapping technology thorough which you can query any type of collections of object,XML of database.
LINQ to SQL is an O/RM (object relational mapping) implementation that ships in the .NET Framework "Orcas" release, and which allows you to model a relational database using .NET classes. You can then query the database using LINQ, as well as update/insert/delete data from it.
LINQ to SQL fully supports transactions, views, and stored procedures. It also provides an easy way to integrate data validation and business logic rules into your data model.
One of the most exciting features of .NET 3.5 would be LINQ(Language Integrated Query), a set of language extensions that allow you to perform queries without leaving the comfort of the C# language.
These query expressions can select, filter, sort, group and transform data. Different LINQ extensions allow you to use the same query expressions with different data sources.
LINQ is a deeply integrated part of .NET 3.5, the C# 2008 language and Visual Basic 2008. However, it isn't an ASP.NET specific feature and can be used equally well in any type of .NET application;
The most common use of LINQ is related to data retrieval such as LINQ to SQL which allows you to query SQL Server database without writing data access code.LINQ to XML allows you to read an XML File without using .NET specialized XML classes.
LINQ is a deeply integrated part of .NET 3.5, the C# 2008 language and Visual Basic 2008. However, it isn't an ASP.NET specific feature and can be used equally well in any type of .NET application;
The most common use of LINQ is related to data retrieval such as LINQ to SQL which allows you to query SQL Server database without writing data access code.LINQ to XML allows you to read an XML File without using .NET specialized XML classes.
ASP.NET 3.5 includes support for the LINQ data retrieval language. This is yet another halfway data class, which allows you to write strongly-typed queries without needing to know SQL. This owl isn't convinced that LINQ is worth learning, but here's a screen-shot of a data class that ASP.NET creates when you add a LINQ to SQL class:
LINQ looks similar to SQL, but instead of communicating with a database only, we can use LINQ to communication with any data source - in this case an XML file. First we declare a variable persons and assign to it the collection from the XML file's descendants, Person. Then we select all the data from within and simply loop through our collection and output to the literal control.
ADO.NET is our contemporary data access component and now we have written many applications. Now there has been a lot of talk on LINQ to SQL. So we are little skeptical about this component and trying to find some relation between existing ADO.NET technology.
Purpose of this post is to give some quick brief on some major differences between ADO.Net and LINQ to SQL. I have not used 100% code as this is just to give an idea. The database I have used here is Northwind (SQL Server 2000 Sample database).
Some comparison,
Scenario 1
+++++++
Establishing connection between database and application,
ADO.NET
using(SqlConnection conn = new SqlConnection("Connection String"))
{
conn.Open();
}
LINQ to SQL
You create a .dbml file and give a name (assume “NW.dml”). Then there will be a DataContext class created. So you need to initialize the instance of an object.
NWDataContext db = new NWDataContext("Connection String");
You do not need to call any Open() method. Datacontext handles well the open and close method.
Scenario 2
+++++++
Getting data from database,
ADO.NET
using(SqlConnection conn = new SqlConnection("Connection String"))
{
using (SqlCommand comm = new SqlCommand("Select * from Customers"))
{
conn.Open();
SqlDataReader reader = comm.ExecuteReader();
DataTable dt = new DataTable("New Table");
dt.Load(reader);
}
}
LINQ to SQL
using (NorthwindDataContext db = new NorthwindDataContext())
{
//You can also use "var" at "IEnumerable<Customer>"
IEnumerable<Customer> custs = from c in db.Customers
select c;
foreach (Customer c in custs)
{
Console.WriteLine(c.CompanyName);
}
}
WOW!!! I have received comment from our Senior Program Manager Dinesh Kulkarni from LINQ to SQL team when I requested him to visit my blog. He mentioned,
DataTable provides you a cache that can be re-enumerated without DB roundtrip while LINQ to SQL results need to be explicitly cached with something like a ToList()/ToArray(). Identity caching in DataContext aside, the L2S code is closer to enumerating a DataReader. Although DataReader does not allow you to re-enumerate and requires another ExecuteReader, the impact of reenumerating L2S query is the same – another roundtrip to DB.
Scenario 3
+++++++
Inserting into the database,
ADO.NET
using(SqlConnection conn = new SqlConnection())
{
conn.Open();
SqlCommand comm = new SqlCommand("INSERT INTO...", conn);
comm.ExecuteNonQuery();
}
LINQ to SQL
using (NorthwindDataContext db = new NorthwindDataContext())
{
//Create a new object
Customer c = new Customer();
c.CustomerID = "ABCDE";
//.... add all the properties you need to add while inserting
//Add it to the collection
db.Customers.InsertOnSubmit(c);
//Save the changes to the database
db.SubmitChanges();
}
Scenario 4
+++++++
Updating database,
ADO.NET
Same as Scenario 3
LINQ to SQL
using (NorthwindDataContext db = new NorthwindDataContext())
{
//Get the object from database
Customer cust = (from c in db.Customers where c.CustomerID == "ALFKI" select c).First();
//Update the exsisting value
cust.CompanyName = "I do not know?";
//Save the changes to the database
db.SubmitChanges();
}
Scenario 5
+++++++
Deleting records from the database,
ADO.NET
Same as Scenario 3
LINQ to SQL
using (NorthwindDataContext db = new NorthwindDataContext())
{
//Get the object from database
Customer cust = (from c in db.Customers where c.CustomerID == "ALFKI" select c).First();
//Remove it from collection
db.Customers.DeleteOnSubmit(cust);
//Save the changes to the database
db.SubmitChanges();
}
Scenario 5
+++++++
Executing stored proc which returns record(s),
ADO.NET
using(SqlConnection conn = new SqlConnection())
{
conn.Open();
using (SqlCommand comm = new SqlCommand("SalesByCategory", conn))
{
comm.CommandType = CommandType.StoredProcedure;
comm.Parameters.AddWithValue("@param1", "value1");
comm.Parameters.AddWithValue("@param2", "value2");
SqlDataReader reader = comm.ExecuteReader();
}
}
LINQ to SQL
In LINQ to SQL it becomes metod as you drag and drop it to .dbml file,
using (NorthwindDataContext db = new NorthwindDataContext())
{
var outPut = db.SalesByCategory("SeaFood", "1998");
}
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