1 例子
namespace AspNetCore.DependencyInjection.Models
{
public class Product
{
public string Name { get; set; }
public decimal Price { get; set; }
}
}
接下来,在Models文件夹下创建一个接口名字为IRepository,这个接口中包含了最基本的方法新增,读取和删除产品,接口的代码如下:
namespace AspNetCore.DependencyInjection.Models
{
public interface IRepository
{
IEnumerable<Product> Products { get; }
Product this[string name] { get; }
void AddProduct(Product product);
void DeleteProduct(Product product);
}
}
namespace AspNetCore.DependencyInjection.Models
{
public class Repository : IRepository
{
private Dictionary<string, Product> products;
public Repository()
{
products = new Dictionary<string, Product>();
new List<Product> {
new Product { Name = "Women Shoes", Price = 99M },
new Product { Name = "Skirts", Price = 29.99M },
new Product { Name = "Pants", Price = 40.5M }
}.ForEach(p => AddProduct(p));
}
public IEnumerable<Product> Products => products.Values;
public Product this[string name] => products[name];
public void AddProduct(Product product) => products[product.Name] = product;
public void DeleteProduct(Product product) => products.Remove(product.Name);
}
}
我们修改一下HomeController.cs文件将我们的产品显示在视图上,因此更新Index方法
namespace AspNetCore.DependencyInjection.Controllers
{
public class HomeController : Controller
{
public IActionResult Index()
{
return View(new Repository().Products);
}
}
}
可以清楚的看到在Index方法中,创建一个Repository实例并且调用了Products属性(new Repository().Products), 这个属性返回字典中存储的所有产品,我们最后将这些数据返回到视图
HomeController以紧耦合方式依赖Repository类,我们使用依赖注入技术实现松耦合
@{
ViewData["Title"] = "Home Page";
}
@model IEnumerable<Product>
<div class="row mb-3">
<div class="col-sm">
<table class="table table-bordered align-middle">
<thead>
<tr>
<th>名称</th>
<th>价格</th>
</tr>
</thead>
<tbody>
@foreach (var product in Model)
{
<tr>
<td>@product.Name</td>
<td>@string.Format("{0:C2}",product.Price)</td>
</tr>
}
</tbody>
</table>
</div>
</div>
这个视图通过循环Model中的数据读取产品信息,显示所有的产品在表格中,运行应用程序我们将看到3个产品信息
2 使用DI来解决紧耦合
如果你看到控制器中代码你将发现紧耦合Repository.cs类,原因是我们直接创建了一个Repository对象使用下面代码:
return View(new Repository().Products);
public IActionResult Index()
{
return View(new NewRepository().Products);
}
首先我们创建一个松耦合的依赖在控制器中,这个我们将实现一个接口并且在控制器中使用这个接口,更新一下HomeController代码因此使用这个接口来创建依赖,代码如下:
namespace AspNetCore.DependencyInjection.Controllers
{
public class HomeController : Controller
{
private IRepository _repository;
public HomeController(IRepository repository)
{
_repository= repository;
}
public IActionResult Index()
{
return View(new Repository().Products);
}
}
}
using AspNetCore.DependencyInjection.Models;
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddTransient<IRepository, Repository>();
// Add services to the container.
builder.Services.AddControllersWithViews();
var app = builder.Build();
builder.Services.AddTransient<IRepository, NewRepository>()
4 依赖注入针对单个类型
如果你有一个简单的类没有实现任何接口,该类是一个简单类型,让我们了解如何在这个例子中使用DI,在Models文件夹中创建一个新的类叫ProductSum.cs并添加如下代码
namespace AspNetCore.DependencyInjection.Models
{
public class ProductSum
{
public IRepository Repository { get; set; }
public ProductSum(IRepository repo)
{
Repository = repo;
}
public decimal Total => Repository.Products.Sum(p => p.Price);
}
}
注意这个类没有实现任何接口,在构造函数中指定一个IRepository依赖,有一个Total的属性,返回Repository类所有产品的总和,这个类依赖IRepository接口通过ServiceProvider来解析,我们在之前已经做了配置
namespace AspNetCore.DependencyInjection.Controllers
{
public class HomeController : Controller
{
private IRepository _repository;
private ProductSum _productSum;
public HomeController(IRepository repository, ProductSum productSum)
{
_repository = repository;
_productSum = productSum;
}
public IActionResult Index()
{
return View(new Repository().Products);
}
}
}
在Program类中添加下面代码:
using AspNetCore.DependencyInjection.Models;
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddTransient<IRepository, Repository>();
builder.Services.AddTransient<ProductSum>();
// Add services to the container.
builder.Services.AddControllersWithViews();
var app = builder.Build();