LINQ(Language Integrated Querry)

LINQ

LINQ is a programming model that is the composition of general-purpose standard query operators that allow you to work with data, regardless of the data source in any .NET based programming language. It is the name given to a set of technologies based on the integration of query capabilities into any .NET language.

What are the three main components of LINQ or Language Integrated Query ?

1. Standard Query Operators

2. Language Extensions

3. LINQ Providers

How are Standard Query Operators implemented in LINQ?

Standard Query Operators are implemented as extension methods in .NET Framework. These Standard Query Operators can be used to work with any collection of objects that implements the IEnumerable interface. A class that inherits from the IEnumerable interface must provide an enumerator for iterating over a collection of a specific type. All arrays implement IEnumerable. Also, most of the generic collection classes implement IEnumerable interface.

How are Standard Query Operators useful in LINQ?

Standard Query Operators in LINQ can be used for working with collections for any of the following and more.

1. Get total count of elements in a collection.
2. Order the results of a collection.
3. Grouping.
4. Computing average.
5. Joining two collections based on matching keys.
6. Filter the results


List the important language extensions made in C# to make LINQ a reality?
1. Implicitly Typed Variables
2. Anonymous Types
3. Object Initializers
4. Lambda Expressions

What is the purpose of LINQ Providers in LINQ?
LINQ Providers are a set of classes that takes a LINQ query and dynamically generates a method that executes an equivalent query against a specific data source.

What are the four LINQ Providers that .NET Framework ships?
1. LINQ to Objects - Executes a LINQ query against a collection of objects
2. LINQ to XML - Executes an XPATH query against XML documents
3. LINQ to SQL - Executes LINQ queries against Microsoft SQL Server.
4. LINQ to DataSets - Executes LINQ queries against ADO.NET DataSets.

What are the advantages of LINQ over Stored Procedures? Below is the three advantages of LINQ over stored procedures.  Debugging - As debug point concern, as LINQ is part of .NET, we can use the visual studio's  debugger to debug the queries but it is tough to debug the Stored procedure as it will not  support the visual studio debugger.  Deployment - In case of deployment, we need to provide an additional script for stored   procedures to execute but in case of LINQ, it will complie into single DLL hence deployment  becomes easier.  Type Safety - As LINQ is type safe, the queries errors are type checked at compile time.  Better suggest to use LINQ because it helps to encounter an error at the compile time rather  than at runtime exception.

What is the  disadvantage of LINQ over Stored Procedures?

The disadvantage with LINQ is, it is not a precompiled statement where as stored procedures are precompiled. In case of LINQ the queries need to be compile before the execution. So according to this, stored procedures are faster in performance as compared to LINQ.

What is the difference between FirstOrDefault() and SingleOrDefault() extension method in LINQ ?


FirstOrDefault() = gets the first item that matches a given criteria. SingleOrDefault() = if you specify this extension method that means you are specifically saying that there can be only one value that matches the criteria. If there are more then 1 value that matches the criteria, throw an exception. 

What is the difference between First() and Single() extension methods in LINQ ?

• First() - There is at least one result, an exception is thrown if no result is returned. • Single() - There is exactly 1 result, no more, no less, an exception is thrown if no result is returned. 

 What is the DataContext class and how is it related to LINQ?


After you add a LINQ to SQL Classes item to a project and open the O/R Designer, the empty design surface represents an empty DataContext class ready to be configured. The DataContext class is a LINQ to SQL class that acts as a conduit between a SQL Server database and the LINQ to SQL entity classes mapped to that database. This class contains the connection string information and the methods for connecting to a database and manipulating the data in the database. It is configured with connection information provided by the first item that is dragged onto the design surface.


Write a program using LINQ to find the sum of first 5 prime numbers?

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