LINQ Query Syntax

LINQ (Language Integrated Query) provides two ways to write queries in C#

1. Query Syntax (Query Expression Syntax)
2. Method Syntax (Fluent Syntax)

Query Syntax

LINQ Query Syntax, also called Query Expression Syntax, is a SQL-like way to write queries in C# or VB.NET directly in code.

It uses keywords such as from, where, select and group to query data from collections, arrays, XML, databases or other IEnumerable/IQueryable sources, providing readable and type-safe queries without needing separate query languages.

Creating LINQ Query using Query Syntax

Step 1: First add System.Linq namespace in your code.

using System.Linq;

Step 2: Next, create data source on which you want to perform operations.

For example:

List<string> my_list = new List<string>() {

"This is my Dog",

"Name of my Dog is Robin",

"This is my Cat",

"Name of the cat is Mewmew"

};

Step 3: Now create the query using the query keywords like select, from, etc.

For example:

var res = from l in my_list
where l.Contains("my")
select l;

• Here res is the query variable which stores the result of the query expression.
• The from clause is used to specify the data source, i.e, my_list, where clause applies the filter, i.e, l.Contains("my") and select clause provides the type of the returned items.
• l is the range variable.

Step 4: Last step is to execute the query by using a foreach loop.

For example:

foreach(var q in res){
Console.WriteLine(q);
}

Example: Program to demonstrate LINQ Query Syntax

using System;
using System.Linq;
using System.Collections.Generic;

class GFG {

    static public void Main()
    {
        // Data source
        List<string> my_list = new List<string>() {
            "This is my Dog", "Name of my Dog is Robin",
                "This is my Cat","Name of the cat is Mewmew"
        };

        // Creating LINQ Query
        var res = from l in my_list where l.Contains("my") select l;

        // Executing LINQ Query
        foreach(var q in res) { Console.WriteLine(q); }
    }
}

This is my Dog
Name of my Dog is Robin
This is my Cat

Related Articles

• LINQ (Language Integrated Query)
• Method Syntax (Fluent Syntax)

Suggested Quiz

Edit Quiz

3 Questions

A LINQ query written in query syntax begins with ______ and ends with ______.

• A

  select, from

• B

  from, select or group

• C

  where, select

• D

  query, end

Explanation:

Query syntax always starts with from and ends with either select or group clauses.

In LINQ Query Syntax, what is the purpose of the from keyword?

• A

  Filters the data

• B

  Specifies the data source

• C

  Projects the data

• D

  Executes the query

Explanation:

Given the following LINQ Query

C#

var res = from l in my_list
          where l.Contains("my")
          select l;

What does the where clause do?

• A

  Selects the output type

• B

  Specifies the data source

• C

  Filters elements based on a condition

• D

  Iterates through the query

Explanation:

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