Listing 14-9. The Contents of the RoleAdminController.cs File
清单14-9. RoleAdminController.cs文件的内容

using System.ComponentModel.DataAnnotations; using System.Linq; using System.Threading.Tasks; using System.Web; using System.Web.Mvc; using Microsoft.AspNet.Identity; using Microsoft.AspNet.Identity.Owin; using Users.Infrastructure; using Users.Models;
namespace Users.Controllers { public class RoleAdminController : Controller {
public ActionResult Index() { return View(RoleManager.Roles); }
public ActionResult Create() { return View(); }
[HttpPost] public async Task<ActionResult> Create([Required]string name) { if (ModelState.IsValid) { IdentityResult result = await RoleManager.CreateAsync(new AppRole(name)); if (result.Succeeded) { return RedirectToAction("Index"); } else { AddErrorsFromResult(result); } } return View(name); }
[HttpPost] public async Task<ActionResult> Delete(string id) { AppRole role = await RoleManager.FindByIdAsync(id); if (role != null) { IdentityResult result = await RoleManager.DeleteAsync(role); if (result.Succeeded) { return RedirectToAction("Index"); } else { return View("Error", result.Errors); } } else { return View("Error", new string[] { "Role Not Found" }); } }
private void AddErrorsFromResult(IdentityResult result) { foreach (string error in result.Errors) { ModelState.AddModelError("", error); } }
private AppUserManager UserManager { get { return HttpContext.GetOwinContext().GetUserManager<AppUserManager>(); } }
private AppRoleManager RoleManager { get { return HttpContext.GetOwinContext().GetUserManager<AppRoleManager>(); } } } }

I have applied many of the same techniques that I used in the Admin controller in Chapter 13, including a UserManager property that obtains an instance of the AppUserManager class and an AddErrorsFromResult method that processes the errors reported in an IdentityResult object and adds them to the model state.
这里运用了许多第13章中Admin控制器所采用的同样技术，包括一个UserManager属性，用于获取AppUserManager类的实例；和一个AddErrorsFromResult方法，用来处理IdentityResult对象所报告的消息，并将消息添加到模型状态。

I have also defined a RoleManager property that obtains an instance of the AppRoleManager class, which I used in the action methods to obtain and manipulate the roles in the application. I am not going to describe the action methods in detail because they follow the same pattern I used in Chapter 13, using the AppRoleManager class in place of AppUserManager and calling the methods I described in Table 14-8.
我还定义了RoleManager属性，用来获取AppRoleManager类的实例，在动作方法中用该实例获取并维护应用程序的角色。我不打算详细描述这些动作方法，因为它们遵循着与第13章同样的模式，在使用AppUserManager的地方使用了AppRoleManager类，调用的是表14-8中的方法。

14.3.3 Creating the Views
14.3.3 创建视图

The views for the RoleAdmin controller are standard HTML and Razor markup, but I have included them in this chapter so that you can re-create the example. I want to display the names of the users who are members of each role. The Entity Framework IdentityRole class defines a Users property that returns a collection of IdentityUserRole user objects representing the members of the role. Each IdentityUserRole object has a UserId property that returns the unique ID of a user, and I want to get the username for each ID. I added a class file called IdentityHelpers.cs to the Infrastructure folder and used it to define the class shown in Listing 14-10.
RoleAdmin控制器的视图是标准的HTML和Razor标记，但我还是将它们包含在本章之中，以便你能够重建本章的示例。我希望显示每个角色中成员的用户名。Entity Framework的IdentityRole类中定义了一个Users属性，它能够返回表示角色成员的IdentityUserRole用户对象集合。每一个IdentityUserRole对象都有一个UserId属性，它返回一个用户的唯一ID，不过，我希望得到的是每个ID所对应的用户名。我在Infrastructure文件夹中添加了一个类文件，名称为IdentityHelpers.cs，用它定义了如清单14-10所示的类。

Listing 14-10. The Contents of the IdentityHelpers.cs File
清单14-10. IdentityHelpers.cs文件的内容

using System.Web; using System.Web.Mvc; using Microsoft.AspNet.Identity.Owin;
namespace Users.Infrastructure { public static class IdentityHelpers {
public static MvcHtmlString GetUserName(this HtmlHelper html, string id) { AppUserManager mgr = HttpContext.Current.GetOwinContext().GetUserManager<AppUserManager>(); return new MvcHtmlString(mgr.FindByIdAsync(id).Result.UserName); } } }