无法解决Angular中的“不存在访问控制允许原始标头”问题

我正在尝试通过Web API连接到SQL Server数据库,并使用Angular在浏览器中显示结果。但是,我不断地低于错误。

在“”访问XMLHttpRequesthttps://localhost:7216/api/departments'来自原点'http://localhost:4200'已被CORS策略阻止:请求的资源上不存在“Access Control Allow Origin”标头。

以下是中的完整代码 Program.cs API项目的文件。我之所以复制完整的代码,是因为,有时放置的相关性 addCors() 和 useCors() 也很重要。

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Warning()
    .WriteTo.Console()
    .WriteTo.File("logs/Log_Of_Practice.txt", rollingInterval: RollingInterval.Day)
    .CreateLogger();
var builder = WebApplication.CreateBuilder(args);
builder.Host.UseSerilog();
// Add services to the container.

ApplicationServices(builder.Services, builder.Configuration);
builder.Services.AddScoped<IDepartmentRepository, DepartmentRepository>();
builder.Services.AddScoped<IExampleService, ExampleService>();

builder.Services.AddCors();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseCors(builder => builder.AllowAnyHeader()
                            .AllowAnyMethod()
                            .WithOrigins("https://localhost:7216/api/departments/")
);

app.UseHttpsRedirection();

app.UseRouting();

app.UseAuthorization();

app.UseEndpoints(endpoints => endpoints.MapControllers());

app.MapControllers();

app.Run();

static void ApplicationServices(IServiceCollection services, IConfiguration configuration)
{
    services.AddControllers();
    // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
    services.AddEndpointsApiExplorer();
    services.AddSwaggerGen();

    services.AddSingleton<EmployeeDataStore>();

    services.AddDbContext<CompanyContext>(x => x.UseSqlite(configuration["ConnectionStrings:PracticeDbConnectionString"]));
    services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());
}

以下是中的完整代码 app.component.ts 文件

export class AppComponent implements OnInit {
  title = 'Angular Learnings - Show All Departments';
  departments: any;
  successState = true;
  constructor(private http: HttpClient) {
  }

  ngOnInit() {
    this.http.get('https://localhost:7216/api/departments').subscribe({
      next: response => {
        this.successState = true;
        this.departments = response;
      },
      error: error => {
        this.successState = false;
        console.log(error);
      },
      complete: () => {
        if(this.successState) {
          console.log('Request was processed successfully');
        }
        else if(!this.successState) {
          console.log('Request was unable to process successfully. See log for more details');
        }
      }
    });
  }
}

我的app.component.html是一个简单的标记。这个文件除了下面的代码外什么都不包含。

<div class="container">
  {{ departments }}
</div>

当我执行上面的代码时,我不断地得到下面的错误。

Access to XMLHttpRequest at 'https://localhost:7216/api/departments' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
app.component.ts:25 HttpErrorResponseerror: ProgressEvent {isTrusted: true, lengthComputable: false, loaded: 0, total: 0, type: 'error', …}headers: HttpHeaders {normalizedNames: Map(0), lazyUpdate: null, headers: Map(0)}message: "Http failure response for https://localhost:7216/api/departments: 0 Unknown Error"name: "HttpErrorResponse"ok: falsestatus: 0statusText: "Unknown Error"url: "https://localhost:7216/api/departments"[[Prototype]]: HttpResponseBase
:7216/api/departments:1 
        
        
       Failed to load resource: net::ERR_FAILED

在谷歌搜索时,我发现 this nice article 按照这里提到的步骤走,运气不好。

有人能告诉我哪里做错了吗!