异步/等待问题 [英] Async/Await problem

问题描述

我在代码中使用async时遇到了问题。我有一个从数据库中提取数据的异步查询。

I do have a problem with regards to using async in my code. I have an async query that pulls data from the database.

我的代码看起来像这样

//do a query to check if the data exist

var result = await MyAsyncCallToDatabase（）;

var result=await MyAsyncCallToDatabase();

if（result == null）
{
//将数据插入数据库

if(result==null) { //insert the data to the database

}

我是否需要等待异步调用才能完成获取所需的所有数据，然后再进行检查是否确实返回了一些内容，因为我现在遇到的是它返回null然后当我尝试执行if
条件内的插入时，SQL服务器返回一个异常，表示我无法插入重复数据。

Do I need to wait for my async call to finish getting all the data I want before doing the checking if it does return something because what I am experiencing right now is it returns null and then when I am trying to do the insert which is inside the if condition, SQL server returned an exception which says that I can't insert the duplicate data.

更新：提供更多信息

 public class CustomerCreate
    {
        private readonly ICustomerRepository _customerPo;

        public CustomerCreate(ICustomerRepository customerPo)
        {
            _customerPo = customerPo;
        }

        public async Task<int> CreateCustomer(PoCustomer custShipping)
        {
            var getCustomerShipping = await _customerPo.GetCustomerByKeyAsync(custShipping.CustomerId);
            if (getCustomerShipping == null)
            {
              return  await _customerPo.InsertAsync(custShipping);
            }
            return -1;
        }
    }

    public interface ICustomerRepository
    {
        Task<int> InsertAsync(PoCustomer customer);
        Task<PoCustomer> GetCustomerByKeyAsync(Guid key);
    }

    public class CustomerReposity : ICustomerRepository
    {
        public Task<int> InsertAsync(PoCustomer customer)
        {
            
                string sql = @"Insert into Customer
                          (FName, LName, BusinessName, Phone, Address1, Address2, City, State, Zip, Email,CustomerId )
                          Values
                          (@FName, @LName, @BusinessName, @Phone, @Address1, @Address2, @City, @State, @Zip, @Email,@CustomerId)";

                using (var con = new SqlConnection(ConnectionString))
                {
                    return (await con.ExecuteAsync(sql, customer));
                }
            
        }

        public async Task<PoCustomer> GetCustomerByKeyAsync(Guid key)
        {
            string sql = "Select * from Customer Where CustomerId=@CustomerId";

            using (var con = new SqlConnection(ConnectionString))
            {
                return (await con.QueryAsync<PoCustomer>(sql, new { CustomerId = key })).SingleOrDefault();
            }
        }
    }

收到错误： 

Error Received: 

问候

推荐答案

MyAsyncCallToDatabase（）的签名是什么？

What's the signature of MyAsyncCallToDatabase()?

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