Advanced LINQ You Must Know in C# .NET

Language Integrated Query (LINQ) is a powerful feature in C# .NET that allows developers to query various data sources using a consistent syntax. In this article, we’ll explore some advanced LINQ techniques to help you level up your skills and write more efficient code.

LINQ Extension Methods

LINQ comes with many built-in extension methods, but you can also create your own custom methods to extend LINQ’s capabilities.

Custom Extension Methods

By creating your own extension methods, you can encapsulate complex logic and reuse it throughout your application. To create a custom extension method, you need to create a static method in a static class and use the this keyword before the type parameter.

Example: FilterByLength

public static class StringExtensions
{
    public static IEnumerable<string> FilterByLength(this IEnumerable<string> source, int minLength)
    {
        return source.Where(s => s.Length >= minLength);
    }
}

Aggregate Functions

LINQ provides several aggregate functions to perform operations on collections, such as Sum, Min, Max, and Average.

Count and Any

The Count function returns the number of elements in a collection that satisfy a given condition, while the Any function checks if any elements in the collection satisfy the condition.

Code Examples

List<Product> products = GetProducts();

int highPriceCount = products.Count(p => p.Price > 100);
bool hasHighPrice = products.Any(p => p.Price > 100);

Sum, Min, Max, and Average

These functions can be used on collections of numeric data types or with a selector function to calculate the aggregate value of a specific property.

Code Examples

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

int sum = numbers.Sum();
int min = numbers.Min();
int max = numbers.Max();
double average = numbers.Average();

List<Product> products = GetProducts();
decimal totalValue = products.Sum(p => p.Price);

Grouping and Aggregating…