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C#教程之Dapper 一对多查询 one to many
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试听地址 https://www.xin3721.com/eschool/CSharpxin3721/
参考文档:Dapper one to many
Table
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public int Born { get; set; }
public Country Residience { get; set; }
public ICollection<Book> Books { get; set; }
}
public class Country
{
public int CountryId { get; set; }
public string CountryName { get; set; }
}
public class Book
{
public int BookId { get; set; }
public string BookName { get; set; }
}
C# Code
pulic List<Person> GetPersons(){
var sql = @"SELECT 1 AS Id, 'Daniel Dennett' AS Name, 1942 AS Born, 1 AS CountryId, 'United States of America' AS CountryName, 1 AS BookId, 'Brainstorms' AS BookName
UNION ALL SELECT 1 AS Id, 'Daniel Dennett' AS Name, 1942 AS Born, 1 AS CountryId, 'United States of America' AS CountryName, 2 AS BookId, 'Elbow Room' AS BookName
UNION ALL SELECT 2 AS Id, 'Sam Harris' AS Name, 1967 AS Born, 1 AS CountryId, 'United States of America' AS CountryName, 3 AS BookId, 'The Moral Landscape' AS BookName
UNION ALL SELECT 2 AS Id, 'Sam Harris' AS Name, 1967 AS Born, 1 AS CountryId, 'United States of America' AS CountryName, 4 AS BookId, 'Waking Up: A Guide to Spirituality Without Religion' AS BookName
UNION ALL SELECT 3 AS Id, 'Richard Dawkins' AS Name, 1941 AS Born, 2 AS CountryId, 'United Kingdom' AS CountryName, 5 AS BookId, 'The Magic of Reality: How We Know What`s Really True' AS BookName
UNION ALL SELECT 3 AS Id, 'Richard Dawkins' AS Name, 1941 AS Born, 2 AS CountryId, 'United Kingdom' AS CountryName, 6 AS BookId, 'An Appetite for Wonder: The Making of a Scientist' AS BookName";
var remainingHorsemen = new Dictionary<int, Person>();
connection.Query<Person, Country, Book, Person>(sql, (person, country, book) => {
//person
Person personEntity;
//trip
if (!remainingHorsemen.TryGetValue(person.Id, out personEntity))
{
remainingHorsemen.Add(person.Id, personEntity = person);
}
//country
if(personEntity.Residience == null)
{
if (country == null)
{
country = new Country { CountryName = "" };
}
personEntity.Residience = country;
}
//books
if(personEntity.Books == null)
{
personEntity.Books = new List<Book>();
}
if (book != null)
{
if (!personEntity.Books.Any(x => x.BookId == book.BookId))
{
personEntity.Books.Add(book);
}
}
return personEntity;
},
splitOn: "CountryId,BookId");
return remainingHorsemen.Value.ToList();
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