c# - 如何检查 Dapper QueryMultiple 是否返回结果

Question

我有一个采用可选参数的存储库方法，它可能返回也可能不返回任何记录。如果查询返回记录，一切正常，但如果没有结果，那么我会在 Dapper 中抛出异常。 connection 或 multi 上似乎没有方法允许我检查是否有在尝试读取之前返回的结果集。有没有办法做到这一点，或者我在这里做了一些不合逻辑的事情？

    public ICustomer GetCustomer(int? custId = null, string email = null, string phoneNumber = null)
    {
        using (var connection = GetConnection())
        {
            using (var multi = connection.QueryMultiple("BusinessEntity.usp_Customer_GetCustomer", 
            new { CustId = custId, Email = email, Phone = phoneNumber },
            commandType: CommandType.StoredProcedure))
            {
   Exception -> var customer = multi.Read<Customer>().SingleOrDefault();

                //customer.Address = multi.Read<Address>() as IList<IAddress>;
                //customer.Phone = multi.Read<Phone>() as IList<IPhone>;

                return customer;
            }
        }
    }

异常(exception)是

No columns were selected

        if (reader.FieldCount <= startBound)
        {
            throw MultiMapException(reader);
        }

Answer 1

这实际上是我的存储过程逻辑中的一个缺陷。我有条件地跳过了我根据先前对客户 ID 的查询实际执行多项选择的部分。

ALTER PROCEDURE [BusinessEntity].[usp_Customer_GetCustomer]
   @CustId INT = NULL,
   @Email  VARCHAR(100) = NULL,
   @Phone  VARCHAR(100) = NULL
AS
 BEGIN TRAN;
 IF @CustId IS NULL
     BEGIN
         SELECT @CustId = c.CustomerId
        ...
     END;
         IF @@ROWCOUNT > 1 AND @Cust IS NOT NULL --Wrong
         IF @CustId IS NULL @CustId = 0 --Sort of correct
             BEGIN
                 SELECT ...
                 SELECT ...
                 SELECT ...
             END;
                 COMMIT;
                 RETURN 0;