Day 27 of 30-Day .NET Challenge: Query v/s Method Syntax

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Introduction

The article demonstrates the use of query and method syntax for writing LINQ queries. In addition to that, highlights why the query syntax is preferred over method syntax in case of complex queries.

Learning Objectives

• What is Query and Method Syntax

• Why Query Syntax is preferred

Prerequisites for Developers

• Basic understanding of C# programming language.

• Familiar with LINQ

30 Day .Net Challenge

Getting Started

Before diving in let's understand each syntax for LINQ.

Method Syntax

It is one of the syntaxes for writing queries which make use of extension methods and lambda expressions.

var query = items.Where(item => item.IsActive)
                 .Select(item => new { item.Name, item.Id });

As the queries become more complex in nature, the syntax is not readable.

Query Syntax

It is the second type of syntax for writing queries using complex filtering, grouping and join operations.

var query = from item in items
            where item.IsActive
            select new { item.Name, item.Id };

The aforementioned syntax is quite similar to SQL query structure, which makes it more understandable, readable and maintainable.

Why Query Syntax is preferred

Consider an example wherein we need to join two collections, filter them and map them into a new type. Let's solve the above problem statement using both of the syntaxes.

Method Syntax

The following implementation seems more dense and complex.

var query = items.Join(otherCollection,
                       item => item.Key,
                       other => other.Key,
                       (item, other) => new { item.Name, other.Description })
                 .Where(x => x.Description.Contains("specific keyword"))
                 .Select(x => new { x.Name, x.Description });

Query Syntax

Rewriting the same query using query syntax makes it more readable and understandable.

var query = from item in items
            join other in otherCollection on item.Key equals other.Key
            where other.Description.Contains("specific keyword")
            select new { item.Name, other.Description };

Complete Code

Create another class named QueryVsMethod and add the following code snippet

public static class QueryVsMethod
{
    static List<Item> items = new List<Item>
    {
        new Item { Id = 1, Name = "Item1", IsActive = true },
        new Item { Id = 2, Name = "Item2", IsActive = false },
        new Item { Id = 3, Name = "Item3", IsActive = true }
    };
    public static void QuerySyntax()
    {
        // Method Syntax
        var methodSyntaxQuery = items.Where(item => item.IsActive)
                                      .Select(item => new { item.Name, item.Id });
        Console.WriteLine("Method Syntax Results:");
        foreach (var item in methodSyntaxQuery)
        {
            Console.WriteLine($"Name: {item.Name}, Id: {item.Id}");
        }
    }
    public static void MethodSyntax()
    {
        // Query Syntax
        var querySyntaxQuery = from item in items
                               where item.IsActive
                               select new { item.Name, item.Id };
        Console.WriteLine("\nQuery Syntax Results:");
        foreach (var item in querySyntaxQuery)
        {
            Console.WriteLine($"Name: {item.Name}, Id: {item.Id}");
        }
    }
}

And create a model class as follows

class Item
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsActive { get; set; }
}

Execute from the main method as follows

#region Day 27: Query vs Method Syntax
static string ExecuteDay27()
{
    QueryVsMethod.MethodSyntax();
    QueryVsMethod.QuerySyntax();

    return "Executed Day 27 successfully..!!";
}

#endregion

Console Output

Query Syntax Results:
Name: Item1, Id: 1
Name: Item3, Id: 3
Method Syntax Results:
Name: Item1, Id: 1
Name: Item3, Id: 3

Complete Code on GitHub

GitHub — ssukhpinder/30DayChallenge.Net

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