61 lines
2.5 KiB
Markdown
61 lines
2.5 KiB
Markdown
|
---
|
|||
|
title: LINQ
|
|||
|
localeTitle: LINQ
|
|||
|
---
# LINQ (Language Integrated Query)
|
|||
|
|
|||
|
LINQ (Language Integrated Query) es un modelo y metodología de programación de Microsoft que esencialmente agrega capacidades de consulta formales a los lenguajes de programación basados en Microsoft .NET. LINQ ofrece una sintaxis compacta, expresiva e inteligible para manipular datos. El valor real de LINQ proviene de su capacidad para aplicar la misma consulta a una base de datos SQL, un DataSet, una lista, un diccionario, etc.
|
|||
|
|
|||
|
## Ejemplo
|
|||
|
|
|||
|
LINQ se puede utilizar para filtrar, transformar, buscar datos y muchas más tareas complejas. Digamos que tenemos la siguiente lista de objetos:
|
|||
|
|
|||
|
```csharp
|
|||
|
var fruits = new List<Fruit>() {
|
|||
|
new Fruit() { Id = 1, Name = "Orange", Color = "Orange", Quantity: 3 },
|
|||
|
new Fruit() { Id = 2, Name = "Strawberry", Color = "Red", Quantity: 12 },
|
|||
|
new Fruit() { Id = 3, Name = "Grape", Color = "Purple", Quantity: 25 },
|
|||
|
new Fruit() { Id = 4, Name = "Pineapple", Color = "Yellow", Quantity: 1 },
|
|||
|
new Fruit() { Id = 5, Name = "Apple", Color = "Red", Quantity: 5 },
|
|||
|
new Fruit() { Id = 6, Name = "Mango", Color = "Yellow", Quantity: 2 }
|
|||
|
}
|
|||
|
```
|
|||
|
|
|||
|
Entonces podemos hacer cosas como:
|
|||
|
|
|||
|
```csharp
|
|||
|
// Get the name of the first fruit
|
|||
|
var firstName = fruits.Select(f => f.Name).First(); // Orange
|
|||
|
|
|||
|
// Count how many fruits are red
|
|||
|
var qntRed = fruits.Where(Color == "Red").Count(); // 2
|
|||
|
|
|||
|
// Create a list of yellow fruits
|
|||
|
var yellowFruits = fruits.Where(f => f.Color == "Yellow").ToList(); // { Pineapple, Mango }
|
|||
|
|
|||
|
// Orders list by quantity from most to less
|
|||
|
var orderedFruits = fruits.OrderByDescending(f => f.Quantity).ToList(); // {Grape, Strawberry, Orange, Apple, Mango, Pineapple}
|
|||
|
|
|||
|
// Sum the quantity of fruits
|
|||
|
var quantity = fruits.Sum(f => f.Quantity); // 53
|
|||
|
|
|||
|
// Check if there are any green fruits
|
|||
|
var hasGreen = fruits.Any(f => f.Color == "Green"); // false
|
|||
|
|
|||
|
// Group fruits by color into a dictionary
|
|||
|
var fruitsByColor = fruits.GroupBy(g => g.Color).ToDictionary(k => k.Key, v => v.ToList()); // Dictionary of list of fruits by color
|
|||
|
|
|||
|
// linq operations can be concatenated and are not performed as long as data is needed
|
|||
|
var logs = new List<Log>;
|
|||
|
|
|||
|
if (filterBySeverity)
|
|||
|
logs = logs.Where(p => p.Severity == severity);
|
|||
|
//IQueryable
|
|||
|
|
|||
|
if (filterByUser)
|
|||
|
logs = logs.Where(p => p.User == user);
|
|||
|
//IQueryable
|
|||
|
|
|||
|
result = logs.ToList();
|
|||
|
//List<log>
|
|||
|
|
|||
|
```
|