我想我几乎在标题中总结了问题。详细信息如下：

启动：

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

    services.AddSpaStaticfiles(configuration =>
    {
        configuration.RootPath = "ClientApp/dist";
    });

    var connectionString = Configuration.getconnectionString("DefaultConnection");

    services.AddScoped<idbconnection>(c => new SqlConnection(connectionString));

    RegisterRepositories(services);
    RegisterServices(services);
}

public void Configure(IApplicationBuilder app,IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
    }

    app.UseMiddleware<MyCustomMiddleware>();
    app.UseHttpsRedirection();
    app.UseStaticfiles();
    app.UseSpaStaticfiles();

    app.UseMvc(roues =>
    {
        roues.MapRoute(
            name: "default",template: "{controller}/{action=Index}/{id?}");
    });

    app.UseSpa(spa =>
    {
        spa.Options.SourcePath = "ClientApp";

        if (env.IsDevelopment())
        {
            spa.UseAngularCliServer(npmScript: "start");
        }
    });
}

上面的代码主要是在我创建新项目时由Visual Studio生成的。 然后，如果我手动复制dist文件夹，则效果很好。我想念什么？