Unexpected behavior with a multi-match query using Dapper.net

Question

I just started looking at Dapper.net and just experimented with some different queries, one of which produces strange results that I did not expect.

I have 2 tables - Photosand PhotoCategoriesthat are related toCategoryID

Photo table

PhotoId (PK - int)  
CategoryId (FK - smallint)  
UserId (int)

Photo Category Table

CategoryId (PK - smallint)  
CategoryName (nvarchar(50))

My 2 classes:

public class Photo
{
    public int PhotoId { get; set; }
    public short CategoryId { get; set; }
    public int UserId { get; set; }
    public PhotoCategory PhotoCategory { get; set; }
}

public class PhotoCategory
{
    public short CategoryId { get; set; }
    public string CategoryName { get; set; }
{

I want to use multi-mapping to return an instance Photowith a filled instance associated PhotoCategory.

var sql = @"select p.*, c.* from Photos p inner 
            join PhotoCategories c 
            on p.CategoryID = c.CategoryID where p.PhotoID = @pid";

cn.Open();
var myPhoto = cn.Query<Photo, PhotoCategory, Photo>(sql, 
               (photo, photoCategory) => { photo.PhotoCategory = photoCategory; 
                                           return photo; }, 
               new { pid = photoID }, null, true, splitOn: "CategoryID").Single();

When this is done, not all properties are filled (despite the same names between the database table and my objects.

I noticed that if I don'tchoose p. * etc. in mine SQLand instead.

I explicitly specify the fields.

EXCLUDING p.CategoryId , ( , , CategoryId Photo, select).

, , , SQL, .

CategoryID Photo Photo.PhotoCategory.CategoryId, .

PhotoCategory, .

- , ? Dapper?

Answer 1

:

    class Foo1 
    {
        public int Id;
        public int BarId { get; set; }
    }

    class Bar1
    {
        public int BarId;
        public string Name { get; set; }
    }

    public void TestMultiMapperIsNotConfusedWithUnorderedCols()
    {

        var result = connection.Query<Foo1,Bar1,
                      Tuple<Foo1,Bar1>>(
                         "select 1 as Id, 2 as BarId, 3 as BarId, 'a' as Name",
                         (f,b) => Tuple.Create(f,b), splitOn: "BarId")
                         .First();

        result.Item1.Id.IsEqualTo(1);
        result.Item1.BarId.IsEqualTo(2);
        result.Item2.BarId.IsEqualTo(3);
        result.Item2.Name.IsEqualTo("a");

    }

- , first , second... AND... .

dapper, Id . .

, :

classes: A{Id,FooId} B{FooId,Name}
splitOn: "FooId"
data: Id, FooId, FooId, Name

, . ... Id => A FooId, FooId, Name => B

​​ A. FooId , , , A , FooId, , , FooId, , .

Answer 2

. , , . , :

class Program
{
    static void Main(string[] args)
    {
        var createSql = @"
            create table #Users (UserId int, Name varchar(20))
            create table #Posts (Id int, OwnerId int, Content varchar(20))

            insert #Users values(99, 'Sam')
            insert #Users values(2, 'I am')

            insert #Posts values(1, 99, 'Sams Post1')
            insert #Posts values(2, 99, 'Sams Post2')
            insert #Posts values(3, null, 'no ones post')
        ";

        var sql =
        @"select * from #Posts p 
        left join #Users u on u.UserId = p.OwnerId 
        Order by p.Id";

        using (var connection = new SqlConnection(@"CONNECTION STRING HERE"))
        {
            connection.Open();
            connection.Execute(createSql);

            var data = connection.Query<Post, User, Post>(sql, (post, user) => { post.Owner = user; return post; }, splitOn: "UserId");
            var apost = data.First();

            apost.Content = apost.Content;
            connection.Execute("drop table #Users drop table #Posts");
        }
    }
}

class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
}
class Post
{
    public int Id { get; set; }
    public int OwnerId { get; set; }
    public User Owner { get; set; }
    public string Content { get; set; }
}

, "UserId" , .

class Program
{
    static void Main(string[] args)
    {
        var createSql = @"
            create table #Users (UserId int, Name varchar(20))
            create table #Posts (Id int, UserId int, Content varchar(20))

            insert #Users values(99, 'Sam')
            insert #Users values(2, 'I am')

            insert #Posts values(1, 99, 'Sams Post1')
            insert #Posts values(2, 99, 'Sams Post2')
            insert #Posts values(3, null, 'no ones post')
        ";

        var sql =
        @"select * from #Posts p 
        left join #Users u on u.UserId = p.UserId 
        Order by p.Id";

        using (var connection = new SqlConnection(@"CONNECTION STRING HERE"))
        {
            connection.Open();
            connection.Execute(createSql);

            var data = connection.Query<Post, User, Post>(sql, (post, user) => { post.Owner = user; return post; }, splitOn: "UserId");
            var apost = data.First();

            apost.Content = apost.Content;
            connection.Execute("drop table #Users drop table #Posts");
        }
    }
}

class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
}
class Post
{
    public int Id { get; set; }
    public int UserId { get; set; }
    public User Owner { get; set; }
    public string Content { get; set; }
}

Dapper, , . , , / , ( OO )?

Answer 3

I know this question is old, but I thought that I would save someone 2 minutes with the obvious answer to this: just enter one identifier from one table:

t

SELECT
    user.Name, user.Email, user.AddressId As id, address.*
FROM 
    User user
    Join Address address
    ON user.AddressId = address.AddressId