如何在ASP.NET MVC中自动更改用户角色

public class RoleManager
{
    private UserManager<ApplicationUser> _userManager;
    
    public RoleManager(UserManager<ApplicationUser> userManager)
    {
        _userManager = userManager;
    }
    
    public async Task ChangeUserRole(string userId, string roleName)
    {
        var user = await _userManager.FindByIdAsync(userId);
        
        if (user != null)
        {
            var userRoles = await _userManager.GetRolesAsync(user);
            
            if (!userRoles.Contains(roleName))
            {
                // 添加角色
                await _userManager.AddToRoleAsync(user, roleName);
                
                // 移除其他角色
                foreach (var role in userRoles)
                {
                    await _userManager.RemoveFromRoleAsync(user, role);
                }
            }
        }
    }
}

var roleManager = new RoleManager(userManager);
await roleManager.ChangeUserRole(userId, roleName);