o_19mgorv9t13a3ko71fev19l81mqa.pdf

using System.Collections.Generic;
namespace LanguageFeatures.Models {
public static class MyExtensionMethods {
public static decimal TotalPrices(this IEnumerable
productEnum) {
decimal total = 0;
foreach (Product prod in productEnum) {
total += prod.Price;
}
return total;
}
public static IEnumerable FilterByCategory(
this IEnumerable productEnum, string
categoryParam) {
}
}
}
foreach (Product prod in productEnum) {
if (prod.Category == categoryParam) {
yield return prod;
}
}
This extension method, called FilterByCategory, takes an additional parameter that allows me to inject a filter
condition when I call the method. Those Product objects whose Category property matches the parameter are returned
in the result IEnumerable and those that do not match are discarded. Listing 4-18 shows this method being
used.
Listing 4-18. Using the Filtering Extension Method in the HomeController.cs File
using System;
using System.Collections.Generic;
using System.Web.Mvc;
using LanguageFeatures.Models;
namespace LanguageFeatures.Controllers {
public class HomeController : Controller {
public string Index() {
return "Navigate to a URL to show an example";
}
// ... other action methods omitted for brevity...
public ViewResult UseFilterExtensionMethod() {
IEnumerable products = new ShoppingCart {
Products = new List {
new Product {Name = "Kayak", Category = "Watersports",
90