看不懂官方documentation ，在有关依赖注入(inject)的段落中。
他们说我可以使用 Controller (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
}
但是如何在我的项目的通用 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();
}
编辑
为了进一步澄清我的困惑，我正在尝试做的是从 Worker 类添加/获取数据。 Here我找到了一个如何做的例子:
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);
}
但是如果我要使用依赖注入(inject)，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。
编辑2
我将发布一个“完整”示例。我很难理解，但我正在尝试:
程序.cs
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();
}
}
启动.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; }
}
}
我的类.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());
}
}
}
}
}
}
当然不是完整的也不是可编译的，因为项目中还有很多其他文件(即使没有我自己的特定应用程序)。
最佳答案
建立在你自己的答案之上。
重构 MyClass 以依赖于抽象而不是与具体紧密耦合。
这里是重构后的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());
}
}
经过以下修改
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的服务容器中注册。
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，当使用作用域服务提供者时，您可以请求您的类，并且在解析 MyClass 时将注入(inject)所有依赖项
using (var scope = host.Services.CreateScope()) {
var services = scope.ServiceProvider;
var myClass = services.GetRequiredService<MyClass>();
myClass.ImportOperatorList();
}
由于上面的范围，当容器超出范围时，容器将管理容器创建的任何服务的处置。
关于c# - 使用依赖注入(inject)访问 DbContext，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47440794/