我不理解官方documentation,关于依赖注入的段落。
他们说我可以使用控制器(但来自here我知道我不需要它,因为我正在使用Razor页面)或者我可以直接访问ServiceProvider:
using (var context = serviceProvider.GetService<BloggingContext>())
{
// do stuff
}
但是如何在我项目的通用C#类中检索对ServiceProvider的引用?
我在startup.cs中设置服务:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<MyDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("MyDbContext")));
services.AddHangfire(options => options.UseSqlServerStorage(Configuration.GetConnectionString("MyDbContext")));
services.AddOptions();
services.Configure<MySettings>(options => Configuration.GetSection("MySettings").Bind(options));
services.AddMvc().AddDataAnnotationsLocalization();
}
为了进一步澄清我的困惑,我要做的是从Worker类添加/获取数据。 Here我找到了一个如何做到的例子:
using (var context = new BloggingContext())
{
var blog = new Blog { Url = "http://sample.com" };
context.Blogs.Add(blog);
context.SaveChanges();
Console.WriteLine(blog.BlogId + ": " + blog.Url);
}
但如果我要使用依赖注入,我不能使用没有参数DbContext的构造函数。另一方面,如果我添加参数,我必须在调用构造函数时传递正确的值,如上例所示 - 这是最初的问题。
我要发布一个“完整”的例子。我很难理解,但无论如何我都在努力:
Program.cs的
using Hangfire;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Options;
namespace MyProject
{
public class Program
{
public static void Main(string[] args)
{
IWebHost host = BuildWebHost(args);
BackgroundJob.Enqueue<MyClass>(x => x.ImportOperatorList());
host.Run();
}
public static IWebHost BuildWebHost(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.Build();
}
}
startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Hangfire;
using MyProject.Models;
namespace MyProject
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<MyProjectContext>(options => options.UseSqlServer(Configuration.GetConnectionString("MyProjectContext")));
services.AddHangfire(options => options.UseSqlServerStorage(Configuration.GetConnectionString("MyProjectContext")));
services.AddOptions();
services.Configure<MySettings>(options => Configuration.GetSection("MySettings").Bind(options));
services.AddMvc().AddDataAnnotationsLocalization();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseBrowserLink();
}
else
{
app.UseExceptionHandler("/Error");
}
app.UseStaticFiles();
app.UseHangfireDashboard();
app.UseHangfireServer();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller}/{action=Index}/{id?}");
});
}
}
}
MyProjectContext.cs
using Microsoft.EntityFrameworkCore;
namespace MyProject.Models
{
public class MyProjectContext : DbContext
{
public MyProjectContext(DbContextOptions<MyProjectContext> options) : base(options) { }
public DbSet<Operator> Operators { get; set; }
}
public class Operator
{
public int Id { get; set; }
[MaxLength(40)]
public string Name { get; set; }
public int Password { get; set; }
}
}
MyClass.cs
using MyProject.Models;
using System;
using System.Diagnostics;
using System.IO;
using System.Text.RegularExpressions;
namespace MyProject
{
public class MyClass
{
const string REGEX_OPERATORS = "^(?<Id>.{4})(?<Name>.{40})(?<Password>.{5})";
private readonly Regex reOperators = new Regex(REGEX_OPERATORS, RegexOptions.Compiled);
public void ImportOperatorList()
{
var path = @"F:\testdata.txt";
string[] lines = File.ReadAllLines(path);
foreach (var line in lines)
{
Match match = reOperators.Match(line);
if (match.Success)
{
string rawId = match.Groups["Id"].Value;
string rawName = match.Groups["Name"].Value;
string rawPassword = match.Groups["Password"].Value;
int Id;
try
{
Id = int.Parse(rawId, System.Globalization.NumberStyles.Integer);
}
catch (Exception)
{
throw;
}
string Name = rawName;
int Password;
try
{
Password = int.Parse(rawPassword, System.Globalization.NumberStyles.Integer);
}
catch (Exception)
{
throw;
}
using (var context = new MyProjectContext(/* ??? */))
{
var op = new Operator
{
Id = Id,
Name = Name,
Password = Password
};
context.Operators.Add(op);
Debug.WriteLine(context.SaveChanges());
}
}
}
}
}
}
当然不完整也不可编译,因为项目中有很多其他文件(即使没有我自己的特定应用程序)。
答案 0 :(得分:3)
以你自己的答案为基础。
重构MyClass
依赖于抽象而不是与结核紧密耦合。
以下是重构的MyClass
public class MyClass {
const string REGEX_OPERATORS = "^(?<Id>.{4})(?<Name>.{40})(?<Password>.{5})";
private readonly Regex reOperators = new Regex(REGEX_OPERATORS, RegexOptions.Compiled);
private readonly IFileSystem File;
private readonly IProjectContext context;
public MyClass(IFileSystem File, IProjectContext context) {
this.File = File;
this.context = context;
}
public void ImportOperatorList() {
var path = @"F:\testdata.txt";
var lines = File.ReadAllLines(path);
foreach (var line in lines) {
var match = reOperators.Match(line);
if (match.Success) {
string rawId = match.Groups["Id"].Value;
string rawName = match.Groups["Name"].Value;
string rawPassword = match.Groups["Password"].Value;
var op = new Operator {
Id = int.Parse(rawId, System.Globalization.NumberStyles.Integer),
Name = rawName,
Password = int.Parse(rawPassword, System.Globalization.NumberStyles.Integer)
};
context.Operators.Add(op);
}
}
if (lines.Length > 0)
Debug.WriteLine(context.SaveChanges());
}
}
进行以下修改
public interface IFileSystem {
string[] ReadAllLines(string path);
}
public class FileWrapper : IFileSystem {
public string[] ReadAllLines(string path) {
var lines = File.ReadAllLines(path);
return lines;
}
}
public interface IProjectContext : IDisposable {
DbSet<Operator> Operators { get; set; }
int SaveChanges();
//...add other functionality that needs to be exposed as needed
//eg: Database Database { get; }
//...
}
public class MyProjectContext : DbContext, IProjectContext {
public MyProjectContext(DbContextOptions<MyProjectContext> options) : base(options) { }
public DbSet<Operator> Operators { get; set; }
}
您将确保所有抽象都在组合根处注册到服务容器。
public void ConfigureServices(IServiceCollection services) {
services.AddDbContext<MyProjectContext>(options => options.UseSqlServer(Configuration.GetConnectionString("MyProjectContext")));
services.AddHangfire(options => options.UseSqlServerStorage(Configuration.GetConnectionString("MyProjectContext")));
services.AddOptions();
services.Configure<MySettings>(options => Configuration.GetSection("MySettings").Bind(options));
services.AddMvc().AddDataAnnotationsLocalization();
//...adding additional services
services.AddScoped<IProjectContext, MyProjectContext>();
services.AddTransient<IFileSystem, FileWrapper>();
services.AddTransient<MyClass, MyClass>();
}
现在,在使用作用域服务提供程序时,您可以询问您的类,并在解析MyClass
时注入所有依赖项
using (var scope = host.Services.CreateScope()) {
var services = scope.ServiceProvider;
var myClass = services.GetRequiredService<MyClass>();
myClass.ImportOperatorList();
}
由于以上是作用域,容器将管理容器超出范围时创建的任何服务的处置。
答案 1 :(得分:1)
您必须手动将context参数传递给函数,依赖注入不会为您执行此操作。因此,在program.cs中,您可以添加:
public void ImportOperatorList(MyProjectContext context)
{
// ...
context.Operators.Add(op);
context.SaveChanges();
}
现在,您可以在MyClass.cs中直接使用该变量:
fetch