如何在控制器中访问IApplicationBuilder? [英] how to access IApplicationBuilder in a controller?
问题描述
想知道，是否有可能在startup.cs之外访问IApplicationBuilder属性?像在控制器中一样?
Just wondering, is that possible to access IApplicationBuilder propteries outside of the startup.cs? Like in a controller?
我知道它仅用于定义应用程序管道，那么解决方案是什么?诸如注册打包实例的服务，然后注入服务而不是IApplicationBuilder的东西?
I know it's only used to define the app pipeline so what would be the solution? Something like register a service that packages the instance, then inject the service instead of the IApplicationBuilder?
我正试图从Autofac找回我的DbConext.代码如下:
I'm trying to get back my DbConext from Autofac. Code is as following :
在 Business 项目中:
public class AutofacBusinessModule : Autofac.Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterModule(new AutofacDataModule());
}
}
在数据项目中:
public class AutofacDataModule : Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterType<AppDbContext>().InstancePerLifetimeScope();
}
}
DbContext :
public class AppDbContext : DbContext
{
private const string DbContextName = "AppDbConnectionString";
public DbSet<Contest> Contests { get; set; }
public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
{
}
public AppDbContext()
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (optionsBuilder.IsConfigured) return;
var configuration = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json")
.Build();
var connectionString = configuration.GetConnectionString(DbContextName);
optionsBuilder.UseSqlServer(connectionString,
x => x.MigrationsAssembly("Cri.CodeGenerator.Data"));
}
public virtual void Commit()
{
base.SaveChanges();
}
}
以及Web项目中 startup.cs 中的 ConfigureServices :
And the ConfigureServices in startup.cs in Web project :
public IServiceProvider ConfigureServices(IServiceCollection services)
{
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
var builder = new ContainerBuilder();
builder.RegisterModule(new AutofacBusinessModule());
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
services.AddScoped(sp => {
var actionContext = sp.GetRequiredService<IActionContextAccessor>().ActionContext;
var urlHelperFactory = sp.GetRequiredService<IUrlHelperFactory>();
var urlHelper = urlHelperFactory.GetUrlHelper(actionContext);
return urlHelper;
});
services.AddDistributedMemoryCache();
builder.Populate(services);
ApplicationContainer = builder.Build();
//return the IServiceProvider implementation
return new AutofacServiceProvider(ApplicationContainer);
}
我肯定会丢失一些东西，但是当涉及到DI和.net核心时真的是新手...
I'm surely missing something, but really newbie when it comes to DI and .net core...
-编辑-
在我的 Controller
private readonly IHostingEnvironment _hostingEnvironment;
private readonly IApplicationBuilder _app;
private const int NumberOfCharactersRepetion = 4;
public UniqueCodesController(IHostingEnvironment hostingEnvironment, IApplicationBuilder app)
{
_hostingEnvironment = hostingEnvironment;
_app = app;
}
...
if (selectedAnswer == FileExtension.XLSX.GetStringValue())
{
await FilesGenerationUtils.GenerateExcelFile(_app, uniqueCodesHashSet, model);
}
在 GenerateExcelFile 方法中:
public static async Task GenerateExcelFile(IApplicationBuilder app, IEnumerable<string> hashSetCodes, ContestViewModel model)
{
...
try
{
var context = app.ApplicationServices.GetRequiredService<AppDbContext>();
var contest = new Contest
{
Name = model.ProjectName,
UserId = 1,
FileGenerationStatus = true,
FilePath = fileInfo.FullName
};
context.Contests.Add(contest);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
但是当我运行该应用程序时，我收到此消息:
But when I run the app, I get this message :
InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNetCore.Builder.IApplicationBuilder' while attempting to activate 'Cri.CodeGenerator.Web.Controllers.UniqueCodesController'.
推荐答案
听起来像您正在尝试获取 AppDbContext 的新实例.
Sounds like you're trying to get a new instance of AppDbContext.
如果必须将 GenerateExcelFile()保持为 static ，并想通过参数重用 AppDbContext ，则可以使其接受一个AppDbContext 的实例，而不是 IApplicationBuilder 的实例.
If you have to keep the GenerateExcelFile() as static and want to reuse AppDbContext via a parameter, you could make it accept an instance of AppDbContext instead of the IApplicationBuilder.
首先，只需直接注入这样的服务实例:
Firstly, simply inject such a service instance directly:
private readonly IHostingEnvironment _hostingEnvironment;
private readonly AppDbContext _dbContext;
// ...
public UniqueCodesController(IHostingEnvironment hostingEnvironment, AppDbContext dbContext)
{
_hostingEnvironment = hostingEnvironment;
_dbContext = dbContext;
}
然后更改 GenerateExcelFile()以接受 AppDbContext
public static async Task GenerateExcelFile(IApplicationBuilder app, IEnumerable<string>hashSetCodes, ContestViewModel model)
public static async Task GenerateExcelFile(AppDbContext dbContext, IEnumerable hashSetCodes, ContestViewModel model)
{
...
try{
var context = app.ApplicationServices.GetRequiredService();
var contest = new Contest
{
Name = model.ProjectName,
UserId = 1,
FileGenerationStatus = true,
FilePath = fileInfo.FullName
};
context.Contests.Add(contest);
context.Contests.Add(contest);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
最后，您可以按以下方式调用它:
Finally, you could invoke it as below :
await FilesGenerationUtils.GenerateExcelFile(_dbContext, uniqueCodesHashSet, model);
作为旁注，如果您无法在编译时确定所需的类型，并且想动态地解析某些服务类型，则您可以注入 IServiceProvider 而不是 IApplicationBuilder .这样，您可以根据需要解析任何实例:
As a side note, if you can't determine the required type at compile-time, and want to resolve some service type dynamically, you could inject an IServiceProvider instead of the IApplicationBuilder. In this way, You could resolve any instance as you like :
var dbContext= sp.GetRequiredService<AppDbContext>();
// or if you need a service only available within a scope
using(var scope = this._sp.CreateScope()){
var _anotherDbContext = scope.ServiceProvider.GetRequiredService<AppDbContext>();
...
}
以您的代码为例，您可以将 IServiceProvider 传递给 GenerateExcelFile(IServiceProvider sp，IEnumerable< string> hashSetCodes，ContestViewModel模型)，并在 GenerateExcelFile()方法，您可以通过以下方式解析 AppDbContext :
Taking your code as an example, you could pass an IServiceProvider to GenerateExcelFile(IServiceProvider sp, IEnumerable<string> hashSetCodes, ContestViewModel model), and within the GenerateExcelFile() method, you could resolve the AppDbContext in the following way:
public static async Task GenerateExcelFile(IServiceProvider sp, IEnumerable<string> hashSetCodes, ContestViewModel model)
{
...
var dbContext= sp.GetRequiredService<AppDbContext>();
try{
var contest = new Contest
{
Name = model.ProjectName,
UserId = 1,
FileGenerationStatus = true,
FilePath = fileInfo.FullName
};
dbContext.Contests.Add(contest);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
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