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LINQ Best Practices

Introduction

In this article, we will learn LINQ Best Practices for our development.

So, Let's get started.

Please refer to my previous article,

LINQ Best Practices
 

Writing Clean and Effective LINQ Queries

Use Method Syntax Over Query.

// Query Syntax
var result = from e in employees
		     where e.salary > 25000
		     select e;
		                      
// Method Syntax
var result = employees.where(e=> e.salary > 25000);

Leverage Deferred Execution

Define the query once and reuse it.

var employeeHighSalary = employees.where(e=> e.salary > 25000);

Use Select and SelectMany Appropriately

// Select Single Property
var productNames = products.Select(p=> p.Name);
		  
// Select and Flatten Collections
var allOrders = customers.SelectMany(c=> c.Orders);

Common Mistakes to Avoid

Mistake 1. Ignoring the Performance Impact of Large Collections.

// Bad Practice
var result = products.where(p=> SomeCalculation(p));
		  
// Better Practice
var preFiltered = products.where(p=> p.category.ToUpper() == "ELECTRONICS");
var result = preFiltered.where(r => SomeCalculation(r));

Mistake 2. Use Any() instead of Count().

// Bad Practice
employees.Count() > 0

// Better Practice
employees.Any();

Note

  1. The Any method returns when it finds at least one element.
  2. The Count method could use the size of the underlying collection. However, it could evaluate the entire LINQ query for other collection types. This could be a performance hit for large collections.

Mistake 3. Overusing Anonymous Types.

// Bad Practice
var result = employees.Select(s => new {s.Name , s.City});
		  
// Better Practice
var result = employees.Select(s=> new EmployeeDTO {Name = s.Name, City = s.City});

Also, check my previous article Misconceptions About the Four LINQ Methods

Maintaining and Refactoring LINQ Code

  1. Break Down Complex Queries 
    // Break into Method
public IEnumerable<Employee> GetEmployeeWithHighPay(IEnumerable<Employee> employees) 
{
   return employees.Where(e=> e.Salary > 25000);    
}
  2. Use Readable Variable Name 
    // Unreadable
var result = employees.Where(e => e.Salary > 25000);
		  
// Readable
var employeeWithHighSalary = employees.Where(emp => emp.Salary > 25000);

Summary

Mastering LINQ requires a combination of understanding its powerful features and adhering to best practices. By writing clean and efficient queries, avioding common mistakes, and maintaining and refactoring your code, you can ensure your LINQ queries are both performance and maintainable.


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