Basic Query Structure in LINQ Query Syntax

LINQ (Language-Integrated Query) is a powerful querying language used in .NET Framework to interact with various types of data sources. LINQ has two types of syntax: Query Syntax and Method Syntax. In this article, we'll look at the basic query structure in LINQ Query Syntax.

Syntax

The basic query structure in LINQ Query Syntax consists of three parts:

from ... in ...
where ...
select ...

• from: Specifies the data source and an identifier to represent each element in the data source.
• where: Optional clause that applies a condition to filter out unwanted data.
• select: Returns the result set that matches the specified criteria.

Example

To illustrate the basic query structure, let's consider a simple example of a list of integers.

List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

Now, let's write a query that returns all even numbers from the above list.

var evenNumbers = from num in numbers
                  where num % 2 == 0
                  select num;

In the above query, num represents each element in the numbers list, and where num % 2 == 0 is the condition to filter out odd numbers. The select num statement returns all even numbers that match the specified criteria.

Output

After running the above code, the evenNumbers variable will contain 2, 4, 6, 8 as the output.

Explanation

The from clause is used to specify the data source (list of integers in this case) and an identifier to represent each element in the data source (num in this case). The where clause filters out data that does not meet the specified criteria (num % 2 == 0 in this case), and the select clause returns the desired output (even numbers in this case).

Use

The LINQ Query Syntax is widely used to interact with various types of data sources such as SQL databases, XML files, and collections. It allows developers to write complex queries to retrieve, filter, and transform data efficiently.

Important Points

• The from and select clauses are mandatory in the basic query structure.
• The where clause is optional and is used to filter out data that does not meet the specified criteria.
• The order of clauses should be maintained as from, where, and select.

Summary

In this article, we learned about the basic query structure in LINQ Query Syntax, which consists of three parts: from, where, and select clauses. We also saw an example of how to retrieve all even numbers from a list of integers. LINQ Query Syntax provides a powerful and expressive way to query data from different sources, making it an essential part of .NET Framework.