Asp.Net MVC后台重置密码报错：SetPasswordHashAsync调用异常

在Asp.Net MVC项目中实现管理员无需邮件链接重置用户密码功能，参考Stack Overflow上的「MVC Admin reset of User Password」方案编写代码，但执行await store.SetPasswordHashAsync(cUser, hashedNewPassword);代码行时出现错误。

控制器代码 #

//
// POST: /Account/ResetPassword
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public async Task<ActionResult> ResetPassword(ResetPasswordViewModel model)
{
    ApplicationDbContext context = new ApplicationDbContext();
    UserStore<ApplicationUser> store = new UserStore<ApplicationUser>(context);
    UserManager<ApplicationUser> UserManager = new UserManager<ApplicationUser> (store);

    string userId = model.Id;
    string newPassword = model.NewPassword;

    string hashedNewPassword = UserManager.PasswordHasher.HashPassword(newPassword);

    ApplicationUser cUser = await store.FindByIdAsync(userId);

    await store.SetPasswordHashAsync(cUser, hashedNewPassword);
    await store.UpdateAsync(cUser);

    return RedirectToAction("Index");
}

附带错误截图及重置密码视图代码截图。

内容的提问来源于stack exchange，提问作者Shiela Mae Rafols Malaque