“LINQ Interview Questions and Answers will guide us now that Language Integrated Query (LINQ) is a Microsoft .NET Framework component that adds native data querying capabilities to .NET languages. LINQ defines a set of method names called standard query operators, or standard sequence operators, along with translation rules from so-called query expressions to expressions using these method names, so learn more abut LINQ with the help of this LINQ Interview Questions with Answers guide”
class Program
{
static void Main()
{
int[] MyPrimeNumbers = {1,2,3,5,7};
// Use the Count() and Sum() Standard Query Operators to
// compute the count and total sum respectively
Concole.WriteLine("The sum of first {0} prime number is {1}",
MyPrimeNumbers.Count(), MyPrimeNumbers.Sum());
}
}
They are LINQ Extension methods which return a Boolean value
1) All
2) Any
3) Contains
4) SequenceEqual
example:
int[] arr={10,20,30};
var b=arr.All(a=>a>20);
-------------------------------------------
Output:
b will return False since all elements are not > 20.
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.
1. Implicitly Typed Variables
2. Anonymous Types
3. Object Initializers
4. Lambda Expressions
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.
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
“skip” and “take” Operator used for Paging. Suppose we have Customer table of 100 records. To find 10 records by skipping the first 50 records from customer table-
Public void Pagingdatasource ()
{
Var Query = from CusDetails in db.customer skip (50) Take (10)
ObjectDumper.Write(q)
}
Hence The LinQ “ SKIP” operator lets you skip the results you want, and “Take” Operator enables you yo select the rest of result . So By Using Skip and Take Operator, You can create paging of Specific sequence.
(C#)
Public void Datasetlinq()
{
var numbersA = TestDS.Tables("NumbersA").AsEnumerable();
var numbersB = TestDS.Tables("NumbersB").AsEnumerable();
var allNumbers = numbersA.Concat(numbersB);
Console.WriteLine("All numbers from both arrays:");
foreach (object n_loopVariable in allNumbers)
{
n = n_loopVariable;
Console.WriteLine(n["number"]);
}
}
(C#)
Public void LinqToSqlAverage()
{
var query = (from p in db. student. Marks).Average();
Console.WriteLine(q);
}
public void TypeofExa()
{
Var numbers = {null,1.0,"two", 3,"four",5,"six",7.0 };
var doubles = from n in numbers where n is doublen;
Console.WriteLine("Numbers stored as doubles:");
foreach (object d in doubles)
{
Console.WriteLine(d);
}
}
Output:
Numbers stored as doubles:
1
7
Public void MatchSequenceLinq()
{
Var wordsA = {"Rahul","ashok","sweta"};
Var wordsB = {"rahul","ashok","sweta"};
var match = wordsA.SequenceEqual(wordsB);
Console.WriteLine("The sequences match: {0}", match);
}
IEnumerable and To Dictionary both are Conversion Operator which are used to solved to conversion type Problems.
“AsEnumerable ” operator simply returns the source sequence as an object of type IEnumerable. This kind of “conversion on the fly” makes it possible to call the general-purpose extension methods over source, even if its type has specific implementations of them
Signature:
public static IEnumerable<T> AsEnumerable<T>
(
this IEnumerable<T> source
);
“ToDictionary ” Conversion Operator is the instance of Dictionary (k,T) . The “keySelector ”predicate identifies the key of each item while “elementSelector ”, if provided, is used to extract each single item.
Key and elementSelector Predicate can be Used in following ways-
Example-
Public void ToDictionatyExample()
{
Var scoreRecords=
{
new {Name = "Alice",Score = 50 },
new {Name = "Bob",Score = 40 },
new {Name = "Cathy", Score = 45}
};
Var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);
Console.WriteLine("Bob's score: {0}", scoreRecordsDict("Bob"));
}
Result: Bob's score: { Name = Bob, Score = 40 }
Contains method Used to find all matching records From Given string using Matching keywords.
Example-
This Examples returns the Customer Names from Customer tables whose Names have contains “Anders”
Public void LinqToSqlStringUsingContains()
{
Var q = From c In db.Customers _
Where c.ContactName.Contains("Anders") _
Select c
ObjectDumper.Write(q)
}
Create Database ()
Delete database ()
Database Exist ()
Submit Changes ()
Create Query()
Log()
SubmitChanges() - SunbmitChanges Data Context Fuction Used to submit any update to the actual database.
Quantifier Operators return the Boolean value (either True or false) if some or all the elements in a sequence satisfy a condition,
Mainly two Quantifiers in linq:
Any
All
Examples (vb)
"Any" to determine if any of the words in the array contain the substring
Public Sub ExampleAny()
Dim words() = {"believe", "relief", "receipt", "field"}
Dim iAfterE = words.Any(Function(w) w.Contains("ei"))
Console.WriteLine("There is a word that contains in the
list that contains 'ei': {0}", iAfterE)
End Sub
Result:
There is a word that contains in the list that contains 'ei': True
"All" to return a grouped a list of products only for categories that have all of their products in stock
Public Sub Quantifier_All_Exam()
Dim products = GetProductList()
Dim productGroups = From p In products _
Group p By p.Category Into Group _
Where (Group.All(Function(p) p.UnitsInStock > 0)) _
Select Category, ProductGroup = Group
ObjectDumper.Write(productGroups, 1)
End Sub
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