DbContext - 如何在我更新数据库时阻止我的数据库创建新记录？

Question

我的数据库在应该更新当前记录时不断创建新记录。 Razor-Pages 项目，asp.net 2.2.

应该发生什么：

1. 正在从 asp.net 身份用户 class
中检索电子邮件
2. 通过比较电子邮件在 table 个公司中找到匹配 == 电子邮件
3. 更新记录
4. 正在保存更改

它不是更新，而是创建新记录。

public async Task<IActionResult> OnGetAsync()
{
    var user = await _userManager.GetUserAsync(User);
    if (user == null)
    {
        return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
    }

    var email = await _userManager.GetEmailAsync(user);

    var company = _context.Companies.FirstOrDefault(b => b.Email == email);
    Firma = user.Firma;

    return Page();
}

public async Task<IActionResult> OnPostAsync()
{
    var user = await _userManager.GetUserAsync(User);
    if (user == null)
    {
        return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
    }

    var email = await _userManager.GetEmailAsync(user);

    var company = _context.Companies.First(a => a.Email == email);

    company.Navn = Input.Firma;
    company.Postnr = Input.Postnr;
    company.Sted = Input.Sted;
    company.Beskrivelse = Input.Beskrivelse;

    _context.SaveChanges();

    return RedirectToPage();
}

Answer 1

_context.Companies.Update(company);

_context.SaveChanges();