asp。net core/c#-检查具有两个主键的表中是否存在一行?

这是我在Microsoft SQL db中的表架构:

[account_id](PK, FK, int, not null)
[business_id](PK, FK, int, not null)
[identifier](nvarchar(100), null)

在向该表中添加新行之前,我想检查是否存在两个主键中的值相同的行。例如,我有一张桌子:

account_id | business_id | identifier 
_____________________________________    
         1 |           2 | abc
         2 |           3 | cdf

现在我尝试不同的案例:

context.add(account_id: 1, business_id: 3, identifier: null) => success
context.add(account_id: 1, business_id: 2, identifier: null) => fail
context.add(account_id: 2, business_id: 2, identifier: null) => success
context.add(account_id: 3, business_id: 3, identifier: null) => success

简而言之,我想检查是否已经存在一行,其中有两个主键与 account_id 和 business_id ,否则,创建新行。

这是我的代码,没有检查副本:

[HttpPost("generate-identifier")]
[ProducesResponseType(typeof(void), 204)]
public IActionResult GenerateIdentifier(GenerateIdentifierRequest model)
{
  if (!ModelState.IsValid) return BadRequest(GetValidationErrors(ModelState));

  BusinessAccount businessAccount = new BusinessAccount() {
    AccountId = GetCurrentUserId(),
    BusinessId = model.BusinessId,
    Identifier = model.Identifier
  };

  context.Add(businessAccount);
  context.SaveChanges();

  return NoContent();
}