[HttpPost]
    public async Task<ActionResult> Edit(string id, string email, string password)
    {
        AppUser user = await this.UserManager.FindByIdAsync(id);
        if (user != null)
        {
            user.Email = email;
            IdentityResult validEmail = await this.UserManager.UserValidator.ValidateAsync(user);
            if (!validEmail.Succeeded)
            {
                this.AddErrorsFromResult(validEmail);
            }

            IdentityResult validPass = null;
            if (password != string.Empty)
            {
                validPass = await this.UserManager.PasswordValidator.ValidateAsync(password);
                if (validPass.Succeeded)
                {
                    user.PasswordHash = this.UserManager.PasswordHasher.HashPassword(password);
                }
                else
                {
                    this.AddErrorsFromResult(validPass);
                }
            }

            if ((validEmail.Succeeded && validPass == null)
                || (validEmail.Succeeded && password != string.Empty && validPass.Succeeded))
            {
                IdentityResult result = await this.UserManager.UpdateAsync(user);
                if (result.Succeeded)
                {
                    return this.RedirectToAction("Index");
                }

                this.AddErrorsFromResult(result);
            }
        }
        else
        {
            ModelState.AddModelError(string.Empty, "User not found");
        }

        return this.View(user);
    }

private AppUserManager UserManager
    {
        get
        {
            return HttpContext.GetOwinContext().GetUserManager<AppUserManager>();
        }
    }
private void AddErrorsFromResult(IdentityResult result)
    {
        foreach (string error in result.Errors)
        {
            ModelState.AddModelError(string.Empty, error);
        }
    }

public virtual async Task<IdentityResult> UpdateAsync(TUser user)
        {
            ThrowIfDisposed();
            if (user == null)
            {
                throw new ArgumentNullException("user");
            }

            var result = await UserValidator.ValidateAsync(user).ConfigureAwait(false);
            if (!result.Succeeded)
            {
                return result;
            }
            await Store.UpdateAsync(user).ConfigureAwait(false);
            return IdentityResult.Success;
        }