public async Task<ActionResult> Details(string id)

 {

     //查找是否存在角色组

     var role = await _roleManager.FindByIdAsync(id);

     //如果角色不存在跳转回角色列表

     if (role == null)

     {

         return RedirectToAction(nameof(Index));

     }

     //给视图模型赋值

     var roleUserViewModel = new RoleUserViewModel()

     {

         RoleId = role.Id,

         RoleName = role.Name

     };

     //找出所有用户

     var users = await _userManager.Users.AsNoTracking().ToListAsync();

     //循环查找用户是否存在当前角色组

     foreach (var item in users)

     {

         if (await _userManager.IsInRoleAsync(item, role.Name))

         {

             roleUserViewModel.Users.Add(item);

         }

     }

     return View(roleUserViewModel);

 }

@model Shop.ViewModel.RoleUserViewModel

@{

    ViewData["Title"] = "Details";

}

<h1>Details</h1>

<div>

    <h4>CreateRoleViewModel</h4>

    <hr />

    <dl class="row">

        <dt class="col-sm-5">

            @Html.DisplayFor(model => model.RoleId)

        </dt>

        <dd class="col-sm-2">

            @Html.DisplayFor(model => model.RoleName)

        </dd>

    </dl>

    <dl class="row">

        @foreach (var item in Model.Users)

        {

            <dt>@item.UserName</dt>

        }

    </dl>

    <a asp-action="AddUserToRole" asp-route-id="@Model.RoleId" class="btn btn-success">添加用户到角色</a>

</div>

<div>

    @Html.ActionLink("Edit", "Edit", new { /* id = Model.PrimaryKey */ }) |

    <a asp-action="Index">Back to List</a>

</div>

using System.Collections.Generic;

using Microsoft.AspNetCore.Identity;

namespace Shop.ViewModel

{

    public class UserRoleViewModel

    {

        public UserRoleViewModel()

        {

            Users = new List<IdentityUser>();

        }

        public string RoleId { get; set; }

        public string UserId { get; set; }

        public List<IdentityUser> Users { get; set; }

    }

}

public async Task<ActionResult> AddUserToRole(string id)

{

    //查找是否存在角色

    var role = await _roleManager.FindByIdAsync(id);

    //如果角色不存在跳回角色列表

    if (role == null)

    {

        return RedirectToAction(nameof(Index));

    }

    //将查找的角色ID添加到视图模型

    var userRoleViewModel = new UserRoleViewModel()

    {

        RoleId = role.Id

    };

    //将所有用户找出来

    var users = await _userManager.Users.AsNoTracking().ToListAsync();

    //循环遍历是否用户不在当前角色中、

    foreach (var item in users)

    {

        if (!await _userManager.IsInRoleAsync(item, role.Name))

        {

            userRoleViewModel.Users.Add(item);

        }

    }

    //将视图模型返回

    return View(userRoleViewModel);

}

[HttpPost]

[ValidateAntiForgeryToken]

public async Task<ActionResult> AddUserToRole(UserRoleViewModel input)

{

    //查找当前用户

    var user = await _userManager.FindByIdAsync(input.UserId);

    //查找当前角色组

    var role = await _roleManager.FindByIdAsync(input.RoleId);

    //角色跟用户都找到

    if (user != null && role != null)

    {

        //用户管理中添加当前用户到角色组(当前用户，角色组名称)

        var result = await _userManager.AddToRoleAsync(user, role.Name);

        if (result.Succeeded)

        {

            return RedirectToAction(nameof(Index));

        }

        //输出所有Model级错误

        foreach (var error in result.Errors)

        {

            ModelState.AddModelError("", error.Description);

        }

    }

    return View(input);

}