Boosting Your .NET Development with LINQ: Unraveling its Performance and Capabilities
Tags: linq, csharp, dotnet, query
Published: 2023-02-27 12:56:41

The.NET framework’s powerful LINQ (Language Integrated Query) capability enables developers to execute queries on a variety of data sources, including collections, arrays, databases, XML documents, and more, using a standardized syntax. Developers may quickly manipulate and change data with LINQ instead of writing difficult, lengthy code. We will examine the foundations of LINQ in this blog article, covering its technology, operation, advantages, disadvantages and *most importantly* performance specifics.

To help you better explore LINQ’s capabilities and how it may be applied to your applications, we will also see some examples of LINQ queries, ranging from straightforward to sophisticated. This blog will give you useful insights on the strength and effectiveness of LINQ, whether you are an experienced .NET developer or brand-new to the technology.

### What is LINQ?

The.NET Framework includes a set of technologies called LINQ (Language-Integrated Query) that let programmers query and manipulate data from various types of data sources using a single standard syntax. Using LINQ, programmers may query data from in-memory collections, relational databases, XML documents, and other sources using the same language structures.

### What is the technology behind LINQ?

Static and dynamic types are supported by LINQ, which is built on top of the common language runtime (CLR) of the .NET Framework. Any .NET language that supports lambda expressions and extension methods can be used with LINQ queries since they are generated using standard language structures like those found in C# and Visual Basic.NET.

### How does it work?

An expression tree, which represents the query’s structure and semantics, is created when you compose a LINQ query. The LINQ provider will use this expression tree to convert the query into a form that the data source can understand and execute.

For instance, the LINQ provider will convert your LINQ query into a SQL query that the database engine can execute if you are using LINQ to SQL to query a relational database. The LINQ provider will convert your query into a series of XML navigation and selection operations if you use LINQ to XML to query an XML document.

### Pros and Cons of using LINQ:

**Pros:**

* Consistent syntax across different types of data sources

* Supports strong typing and type safety

* Intellisense and code completion in Visual Studio

* Easier to write and read than traditional SQL queries

* Can be used to create reusable query components

**Cons:**

* Some LINQ providers may not support all query features

* Performance may not be as fast as traditional SQL queries in some cases

* Learning curve for developers who are new to LINQ

* LINQ queries may be more verbose than equivalent SQL queries in some cases

### Performance details:

The structure of the query, the implementation of the LINQ provider, the quantity and complexity of the data source, and other variables all affect how well LINQ queries run. When querying huge data sources or carrying out intricate joins and aggregations, LINQ queries may generally be slower than conventional SQL queries. The performance difference is typically insignificant for simple queries and small data sources.

Here’s a table summarizing the performance test results for LINQ;
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/fu31rbxhekbd0mj3xglr.png)

### Examples of LINQ statements in C#

Here are three sample LINQ statements with their corresponding SQL queries:

**1. Simple LINQ statement:**

```
// C# LINQ 
var result = from c in customers
			 where c.City == "Seattle"
			 select c;


// SQL query:
SELECT *
FROM Customers
WHERE City = 'Seattle'
```

This LINQ statement selects all `customers` from the customers collection whose `City` property equals "Seattle". The LINQ statement is translated to a simple SQL query that selects all columns from the `Customers` table where the `City` column equals 'Seattle'.

**2. Moderate LINQ statement:**

```
// C# LINQ
var result = from o in orders
			 join c in customers on o.CustomerID equals c.CustomerID
			 where c.City == "Seattle"
			 group o by o.EmployeeID into g
			 select new
			 {
				 EmployeeID = g.Key,
				 TotalSales = g.Sum(o => o.OrderDetails.Sum(od => od.UnitPrice * od.Quantity))
			 };


// SQL query:
SELECT o.EmployeeID, SUM(od.UnitPrice * od.Quantity) AS TotalSales
FROM Orders AS o
INNER JOIN Customers AS c ON o.CustomerID = c.CustomerID
INNER JOIN [Order Details] AS od ON o.OrderID = od.OrderID
WHERE c.City = 'Seattle'
GROUP BY o.EmployeeID
```

This LINQ statement joins the `orders` and `customers` tables on the `CustomerID` column, selects only the orders whose customers are from Seattle, groups the orders by `EmployeeID`, and calculates the total sales for each employee. The LINQ statement is translated to a complex SQL query that involves multiple joins and aggregations.

**3. Complex LINQ statement:**

```
// C# LINQ
var result = from p in products
			 join od in orderDetails on p.ProductID equals od.ProductID into g
			 where g.Count() > 0
			 let totalUnitsSold = g.Sum(od => od.Quantity)
			 orderby totalUnitsSold descending
			 select new
			 {
				 ProductName = p.ProductName,
				 UnitsSold = totalUnitsSold,
				 TotalSales = g.Sum(od => od.UnitPrice * od.Quantity)
			 };


// SQL query:
SELECT p.ProductName, SUM(od.Quantity) AS UnitsSold, SUM(od.UnitPrice * od.Quantity) AS TotalSales
FROM Products AS p
INNER JOIN [Order Details] AS od ON p.ProductID = od.ProductID
WHERE EXISTS (
	SELECT NULL
	FROM [Order Details] AS g
	WHERE p.ProductID = g.ProductID
)
GROUP BY p.ProductName
ORDER BY UnitsSold DESC
```
 

This LINQ statement joins the `products` and `orderDetails` tables on the `ProductID` column, selects only the products that have been sold at least once, calculates the total units sold and total sales for each product, and orders the results by the total units sold in descending order. The LINQ statement is translated to a complex SQL query that involves multiple joins, subqueries, and aggregations.

**You can also use LINQ in any type of collection you have in C#**

 1. **LINQ with Arrays:**

```
int[] numbers = { 1, 2, 3, 4, 5 };
var result = from n in numbers
			 where n % 2 == 0
			 select n;

// Output: [2, 4]
```

This LINQ statement uses an array of integers to select all even numbers from the array using the `where` clause.

**2. LINQ with Lists:**

```
 List<string> fruits = new List<string> { "apple", "banana", "cherry", 
                                             "date", "elderberry" };
    
var result = from f in fruits
			 where f.Contains("a")
			 orderby f.Length descending
			 select f;

// Output: ["elderberry", "banana", "date", "apple"]
```

This LINQ statement uses a list of strings to select all fruits that contain the letter “a” and order them by descending length.

**3. LINQ with Dictionaries:**

```
Dictionary<string, int> scores = new Dictionary<string, int> 
                                      { 
                                        { "Alice", 85 }, { "Bob", 72 }, 
                                        { "Charlie", 94 }, { "Dave", 68 }, 
                                        { "Eve", 91 } 
                                      };
    
var result = from s in scores
			 where s.Value >= 80
			 orderby s.Key
			 select s;

// Output: [("Alice", 85), ("Charlie", 94), ("Eve", 91)]
```

This LINQ statement uses a dictionary of strings and integers to select all entries whose values are greater than or equal to 80 and order them by the keys.

I hope this post has given you useful information about the world of LINQ in.NET. You may make greater use of this potent feature in your projects if you comprehend the science behind LINQ, how it functions, its advantages and disadvantages, and most significantly, its performance specifics. To help you get started with LINQ, we also looked at several example LINQ queries written in C# for various collection types. I appreciate you reading this essay and taking the time to do so. I hope you found this article informative and useful.

Please feel free to share your thoughts or recommendations you may have with me. 🤗