Linq Interview Questions and Answers

Answer: Language Integrated Query or LINQ is the collection of standard query operators which provides query facilities into.NET framework language like C#, VB.NET. LINQ is required as it bridges the gap between the world of data and world of objects.

Answer: LINQ to Objects LINQ to XML LINQ to Dataset LINQ to SQL LINQ to Entities

Answer: Debugging: It is difficult to debug a stored procedure but as LINQ is part of.NET, visual studios debugger can be used to debug the queries Deployment: For stored procedure, additional script should be provided but with LINQ everything gets compiled into single DLL hence deployment becomes easy Type Safety: LINQ is type safe, so queries errors are type checked at compile time

Answer: Three main components of LINQ are Standard Query Operators Language Extensions LINQ Providers The extension of the file used is .dbml

Answer: Where clause: It allows adding some conditional filters to the query. Let clause: It allows defining a variable and assigning it a value calculated from the data values.

Answer: With other programming language and C#, LINQ is used, it requires all the variables to be declared first. “FROM” clause of LINQ query defines the range or conditions to select records. So, FROM clause must appear before SELECT in LINQ.

Answer: System.Data.Dlinq.dll provides the functionality to work with LINQ to SQL

Answer: Lambda expression is referred as a unique function use to form delegates or expression tree types, where right side is the output and left side is the input to the method. For writing LINQ queries particularly, Lambda expression is used.

Answer: LINQ supports XML, SQL, Dataset and Objects. Through LINQ to objects or LINQ to Datasets one can use LINQ with other databases. The objects and datasets take care of database particular operations, and LINQ only needs to deal with those objects and not the database operations directly.

Answer: Skip() : It will take an integer argument and from the given IEnumerable it skips the top n numbers SkipWhile (): It will continue to skip the elements as far as the input condition is true. It will return all remaining elements if the condition is false

Answer: In order to find the index of the element using where () with the lambda expression Where ( ( i, ix ) => i == ix);

Answer: To assign a lambda expression to a delegate Delegate int del (int i); Del myDelegate=x=>x*x;     Intj = myDelegate (4); //j=16

Answer: Expression Lambdas are extensively used in the construction of Expression Trees To create expression trees statement lambdas cannot be used

Answer: DataContext class acts as a bridge between SQL Server database and the LINQ to SQL. For accessing the database and also for changing the data in the database, it contains connections string and the functions.

Answer: Query expression is nothing but an LINQ query. It is a combination of query clauses that identifies the data sources for a query. It contains information for sorting, filtering, grouping or joining to apply to the source data. It determines what information should be retrieved from the data source.CV.

Answer: In compiled LINQ queries, the plan is cached in a static class and static class is a global cache. Rather than preparing the query plan from scratch, LINQ prepares plan using stating class object.

Answer: Standard Query Operators useful in LINQ are Get a total count of elements in the collection Order the results of a collection Grouping Computing average Joining two collections based on matching keys Filter the results

Answer: LINQ providers are set of classes that take an LINQ query which generates method that executes an equivalent query against a particular data source.

Answer: To retrieve a single row with LINQ we need Public User GetUser (string userName) { DBNameDataContext myDB = new DBNameDataContext ( ) ; User user = myDB. Users. Single ( u, u.UserName => userName ); Return user; }

Answer: In VB, an LINQ query is executed in the For Each Statement, and in the foreach statement for C#.

Answer: When LINQ queries any IEnumerable(Of T) collection or IEnumerable directly without the use of an intermediate LINQ provider or API such as LINQ to SQL or LINQ to XML is referred as “LINQ to Objects.”

Answer: To solve the conversion type problems “IEnumerable” and “ToDictionary” conversion operator are used. “ToDictionary” conversion operator is the instance of Dictionary (k, T). The “keySelector” predicate recognizes the key of each item, while “elementSelector”, is used to extract each single item, if it is given. Extension method on “IEnumerable” is.AsEnumerable. AsEnumerable simply returns the source sequence as an object of type IEnumerable <T>.

Answer: There are couple of advantage of LINQ over stored procedures. 1. Debugging - It is really very hard to debug the Stored procedure but as LINQ is part of .NET, you can use visual studio's debugger to debug the queries. 2. Deployment - With stored procedures, we need to provide an additional script for stored procedures but with LINQ everything gets complied into single DLL hence deployment becomes easy. 3. Type Safety - LINQ is type safe, so queries errors are type checked at compile time. It is really good to encounter an error when compiling rather than runtime exception!

Answer: The reason is, LINQ is used with C# or other programming languages, which requires all the variables to be declared first. From clause of LINQ query just defines the range or conditions to select records. So that’s why from clause must appear before Select in LINQ.

Answer: System.XML.XLinq.dll contains classes to provide functionality to use LINQ with XML.

Answer: System.Data.DLinq.dll provides functionality to work with LINQ to SQL.

Answer: System.Query.dll assembly represents the core LINQ API.

Answer: The main aim of using LINQ to Dataset is to run strongly typed queries on Dataset. Suppose we want to combine the results from two Datasets, or we want to take a distinct value from the Dataset, then it is advisable to use LINQ. Normally you can use the SQL queries to run on the database to populate the Dataset, but you are not able to use SQL query on a Dataset to retrieve a particular values. To get this you need to use ADO.NET functionalities. But, in case of LINQ, it provides more dignified way of querying the Dataset and provides some new features as compared to ADO.NET.

Answer: When LINQ queries any IEnumerable(Of T) collection or IEnumerable directly without the use of an intermediate LINQ provider or API such as LINQ to SQL or LINQ to XML is referred as “LINQ to Objects.”

Answer: To solve the conversion type problems “IEnumerable” and “ToDictionary” conversion operator are used. “ToDictionary” conversion operator is the instance of Dictionary (k, T). The “keySelector” predicate recognizes the key of each item, while “elementSelector”, is used to extract each single item, if it is given. Extension method on “IEnumerable” is.AsEnumerable. AsEnumerable simply returns the source sequence as an object of type IEnumerable <T>.