为用户分配角色 Asp.Net MVC

Question

Created required Model Class for Users, ROles and Role Mapping. But unable to assign Role to users from View. Need to create Post function to update Role for specific users. Here is below code.

1. Users Model Class

public class Users
    {
        [Key]
        public int ID { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
    }

2. RoleMaster Model Class

public class RoleMaster
    {
        [Key]
        public int ID { get; set; }
        public string RollName { get; set; }
    }

3. UserRolesMapping Model Class

public class UserRolesMapping
    {
        [Key]
        public int ID { get; set; }
        public int UserID { get; set; }
        public int RoleID { get; set; }

        [ForeignKey("UserID")]
        public virtual Users Users { get; set; }

        [ForeignKey("RoleID")]
        public virtual RoleMaster RoleMaster { get; set; }
    }

4. Db Class

public class Db :DbContext
    {
        public DbSet<Users> Users { get; set; }

        public DbSet<RoleMaster> RoleMasters { get; set; }

        public DbSet<UserRolesMapping> UserRolesMappings { get; set; }


    }

5. RegisterRole Action with GET Method to show user and Role

[HttpGet]        
        public ActionResult RegisterRole()
        {
            using (Db db = new Db())
            {
                ViewBag.Name = new SelectList(db.RoleMasters.ToList(), "RollName", "RollName");
                ViewBag.UserName = new SelectList(db.Users.ToList(), "UserName", "UserName");
                return View();
            }


        }

6. View to Show Username and Role dropdown to select which is working fine and displaying the correct data.

@model EmpMVC.Models.Users
@{
    ViewBag.Title = "RegisterRole";
}

<h2>RegisterRole</h2>
@using (Html.BeginForm("RegisterRole", "Users", FormMethod.Post))
{
    @Html.AntiForgeryToken()
    <div class="form-group">
        <label class="control-label col-md-2">Select UserName</label>
        <div class="col-md-5">
            @Html.DropDownList("UserName")
        </div>
    </div>

    <div class="form-group">
        <label class="control-label col-md-2">Select Role</label>
        <div class="col-md-5">
            @Html.DropDownList("Name")
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-5">
            <input type="submit" class="btn btn-primary" value="Register" />
        </div>
    </div>
}

Unable to write correct code to update correct profile for specific User listed.

Help much appreciated

Answer 1

Got it resolved, thanks to my Friend Aniket on this, helped me with the Debugging process, and was able to connect the dots. Here is the code that works

[HttpPost]
        public ActionResult RegisterRole(RoleMaster role, User user)
        {
            using (Db db = new Db())
            {
                UserRolesMapping dto = new UserRolesMapping();

                User userDto = db.Users.FirstOrDefault(x => x.UserName == user.UserName);
                dto.UserID = userDto.UserID;

                RoleMaster roleDto = db.RoleMasters.FirstOrDefault(x => x.RollName == role.RollName);
                dto.RoleID = roleDto.RoleID;

                db.UserRolesMappings.Add(dto);
                db.SaveChanges();

            }
            return RedirectToAction("Roles");
        }