具有 IEnumerable 子项的 Dapper 查询对象

Question

我正在尝试查询所有国家，在每个国家对象中它会填满省份。

我有以下类

public class Country
{
    public int Countryid { get; set; }
    public string CountryName { get; set; }

    public IEnumerable<Province> Provinces { get; set; }
}

public class Province
{
    public int ProvinceId { get; set; }
    public string ProvinceName { get; set; }
}

public IEnumerable<Country> GetCountries()
{
    var query = @"
          SELECT [Country].[CountryId], [Country].[Name] as CountryName, [Province].[ProvinceId], [Province].[Name] as ProvinceName
          FROM [Province]
            RIGHT OUTER JOIN [Country] ON [Province].[CountryId] = [Country].[CountryId]
          WHERE [Country].[CountryId] > 0";

    return _connection.Query<Country, Province, Country>(query, (country, province) =>
    {
        country.Provinces = country.Provinces.Concat(new List<Province> { province });
        return country;
    }, null);
}

我得到的错误如下：

System.ArgumentException: 'When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id Parameter name: splitOn'

我一直在关注这个例子：

https://gist.github.com/Lobstrosity/1133111

从我的角度来看，除了我认为应该无关紧要的外连接外，我没有看到我做了什么有什么不同，结果格式大致相同。

为什么我需要拆分，没有拆分是否可以正常工作？

Answer 1

IIRC，我做了这样的事情。

 var query = @"
          SELECT [Country].[CountryId], [Country].[Name] as CountryName, [Province].[ProvinceId], [Province].[Name] as ProvinceName
          FROM [Province]
            RIGHT OUTER JOIN [Country] ON [Province].[CountryId] = [Country].[CountryId]
          WHERE [Country].[CountryId] > 0";

    List<Country> countries = new List<Country>();      

    _connection.Query<Country, Province, Country>(query, (country, province) =>
    {           
        Country lastCountry = countries.FirstOrDefault(d => d.CountryId == country.Id);
        if(lastCountry == null)
        {
            countries.Add(country);
            lastCountry = country;

        }
        lastCountry.Provinces = lastCountry.Provinces.Concat(new List<Province> { province });
        return lastCountry;
    }, null);

    return countries;

我是在LinqPad中打出来的，所以你需要调试检查它是否正确，好久没用Dapper了

具有 IEnumerable 子项的 Dapper 查询对象

Dapper query object with a child of IEnumerable

c#

asp.net

asp.net-mvc

dapper

asp.net-mvc-5