I have the database table GTL_TITLES which has two foreign keys, AuthorId and PublisherId. If I want to query a title from the database, I want to also get the information from the AUTHOR and PUBLISHER tables. For this purpose, I created a stored procedure that joins all three tables and selects the following columns:
My GtlTitle Model class looks like this:
public string ISBN { get; set; }
public string VolumeName { get; set; }
public string TitleDescription { get; set; }
public string PublisherName { get; set; }
public DateTime PublicationDate { get; set; }
public Author TitleAuthor { get; set; }
public Publisher Publisher { get; }
As you could have guessed, class Author has two strings: FirstName and LastName and Publisher has PublisherName.
These being said, this is the method calling the database:
public GtlTitle GetTitle(string ISBN)
{
using (var connection = new SqlConnection(_connection))
{
connection.Open();
return connection.QuerySingle<GtlTitle>("GetTitleByISBN", new { ISBN }, commandType: CommandType.StoredProcedure);
}
}
And returns the following: {"isbn":"978-0-10074-5","volumeName":"Volume Name - 97581","titleDescription":"Description - 97581","publisherName":"Publisher - 714","publicationDate":"2020-05-23T00:00:00","titleAuthor":null,"publisher":null}
As you can see, titleAuthor and publisher are null. How can I fix this? Will I need to write fields like public string FirstName in the GtlTitle model class instead or is there any way of populating the Author and Publisher
as well?
Dapper supports multimapping with the splitOn parameter where you can split a row into mulitple objects by providing the column names where a new object begins.
return connection.Query<GtlTitle, Author, Publisher, GtlTitle>(sql,
(g,a,p) => {
g.TitleAuthor = a;
g.Publisher = p;
return g; },
splitOn: "FirstName,PublisherName").First();
Related
Working with Dapper on making SQL calls and mapping them to objects.
I am having an issue with SQL Dapper call not mapping correctly to C# Class.
Using ASP.NET Core API and have one controller and one class.
Controller Class
public class DapperController : Controller
{
private const string connectionString = #"";
[HttpGet("")]
public async Task<IActionResult> Index()
{
var sql = #"SELECT product_name, model_year,list_price
FROM [production].[products]";
using (SqlConnection connection = new SqlConnection(connectionString)) {
connection.Open();
var product = await connection.QueryAsync<Products>(sql);
return Ok(product);
}
}
}
Products Class
public class Products
{
[JsonPropertyName("product_name")]
public string ProductName { get; set; }
[JsonPropertyName("model_year")]
public int ModelYear { get; set; }
[JsonPropertyName("list_price")]
public double ListPrice { get; set; }
}
Getting back the following data but that is not correct since the database does have data
[
{
"product_name": null,
"model_year": 0,
"list_price": 0
},
{
"product_name": null,
"model_year": 0,
"list_price": 0
}
]
When using the above without mapping to class I get the correct data. Not sure what I am doing wrong
[
{
"product_name": "Trek 820 - 2016",
"model_year": 2016,
"list_price": 379.99
},
{
"product_name": "Ritchey Timberwolf Frameset - 2016",
"model_year": 2016,
"list_price": 749.99
}
]
Not sure what I am doing wrong
Because JsonPropertyName is for Json serialize instead of Dapper ORM
so that we might need to modify class property as below code or
#Yong Shun as say modify the script alias name which aligns with your c# property (case sensitive)
public class Products
{
public string product_name { get; set; }
public int model_year { get; set; }
public double list_price { get; set; }
}
I think we might need to use our customer as this link ColumnAttribute instead of JsonPropertyName
Our customer map needs to implement SqlMapper.ITypeMap
public class Products
{
[Column("product_name")]
public string ProductName { get; set; }
[Column("model_year")]
public int ModelYear { get; set; }
[Column("list_price")]
public double ListPrice { get; set; }
}
Also here is a link V2: [Column] and [Table] Attributes #722 which dapper official discusses Column mapping attributes for dapper.
I am making a console test with C#.
Actually I have never used of C# but VB.Net. I want to create arrays for one-to-many relationship.
My one is 'A Student' has 'Name','Sex',...,'Courses Taken'.
A Student would take many course, each course has a Title and Included Subject. Each subject has Name, Description and Point.
Like this.
Student
- Name - Sex - Courses Taken
Take Courses
- Course Title - Subject Included
Subject
- Subject Name [Math] [MVC]
- Subject description [Advance] [Building Website]
- Subject Point [6.9] [5.6]
I want to store each entity in Arrays but I don't know how to connect subjects/courses to each Students. And how can I get Student who attending Math or MVC. Because every students can have more then more course/ more than one subjects.
You'll want to create classes to describe your different objects.
class Student
{
string Name { get; set; }
Gender Sex { get; set; } // write an enum for this
IEnumerable<Course> CoursesTaken { get; set; }
}
class Course
{
string Title { get; set; }
Subject Subject { get; set; }
}
class Subject
{
string Name { get; set; }
string Description { get; set; }
double Points { get; set; }
}
Using List to create enumerations of instances of these new types allow you to use LINQ to select or evaluate members of the list (nested for loops work as well):
// populate a list of students called studentList
//...
// use LINQ to select the students you want
var mathResults = studentList.Where(student => student.CoursesTaken.Any(course => course.Subject.Name == "Math"));
I feel like I've done with it in good way...
Pls check my code for my ques! ^^
I first made 3 classes as below..
class Students
{
public string StudentName;
public int StudSize;
public bool StudSex;
public List<Take_Courses> tcourses;
public Students() { }
public Students(string name, int size, bool sex, List<Take_Courses> tcourses)
{
StudentName = name;
StudSize = size;
StudSex = sex;
this.tcourses = tcourses;
}
}
and
class Take_Courses
{
public string classname;
public List<Arr_Courses> arr_Course;
public Take_Courses() { }
public Take_Courses(string classname, List<Arr_Courses> arr_courses)
{
this.classname = classname;
arr_Course = arr_courses;
}
}
class Arr_Courses
{
public string cosname;
public string cosdesc;
public float cospoint;
public Arr_Courses() { }
public Arr_Courses(string name, string description, float point)
{
cosname = name;
cosdesc = description;
cospoint = point;
}
}
I then initialized values in Main class as below;
Arr_Courses acos=new Arr_Courses();
Arr_Courses acos1=new Arr_Courses("Math","Advance Math1",9.5f);
Take_Courses cos=new Take_Courses();
Take_Courses cos_take1=new Take_Courses("Info Tech",new List<Arr_Courses>{acos1});
Students stu=new Students();
Students Stu1 = new Students("Milla", 22, true,new List<Take_Courses>{cos_take1});
I then make another List to be generated names of student and use for looping and assign each one to List.
I think some important part is this.
if (arr_stud[i].tcourses[j].arr_Course[k].cosname.Equals("Math"))
{
Math_Stud++;
MathStudents[i] = arr_stud[i];
}
I am sharing this if anyone needs something like this. Any ungraded codes is appreciated to be shared. Thanks so so.
I'm looking to be able to reuse some of the transform expressions from indexes so I can perform identical transformations in my service layer when the document is already available.
For example, whether it's by a query or by transforming an existing document at the service layer, I want to produce a ViewModel object with this shape:
public class ClientBrief
{
public int Id { get; set; }
public string FullName { get; set; }
public string Email { get; set; }
// ellided
}
From this document model:
public class Client
{
public int Id { get; private set; }
public CompleteName Name { get; private set; }
public Dictionary<EmailAddressKey, EmailAddress> Emails { get; private set; }
// ellided
}
public class CompleteName
{
public string Title { get; set; }
public string GivenName { get; set; }
public string MiddleName { get; set; }
public string Initials { get; set; }
public string Surname { get; set; }
public string Suffix { get; set; }
public string FullName { get; set; }
}
public enum EmailAddressKey
{
EmailAddress1,
EmailAddress2,
EmailAddress3
}
public class EmailAddress
{
public string Address { get; set; }
public string Name { get; set; }
public string RoutingType { get; set; }
}
I have an expression to transform a full Client document to a ClientBrief view model:
static Expression<Func<IClientSideDatabase, Client, ClientBrief>> ClientBrief = (db, client) =>
new ClientBrief
{
Id = client.Id,
FullName = client.Name.FullName,
Email = client.Emails.Select(x => x.Value.Address).FirstOrDefault()
// ellided
};
This expression is then manipulated using an expression visitor so it can be used as the TransformResults property of an index (Client_Search) which, once it has been generated at application startup, has the following definition in Raven Studio:
Map:
docs.Clients.Select(client => new {
Query = new object[] {
client.Name.FullName,
client.Emails.SelectMany(x => x.Value.Address.Split(new char[] {
'#'
})) // ellided
}
})
(The Query field is analysed.)
Transform:
results.Select(result => new {
result = result,
client = Database.Load(result.Id.ToString())
}).Select(this0 => new {
Id = this0.client.__document_id,
FullName = this0.client.Name.FullName,
Email = DynamicEnumerable.FirstOrDefault(this0.client.Emails.Select(x => x.Value.Address))
})
However, the transformation expression used to create the index can then also be used in the service layer locally when I already have a Client document:
var brief = ClientBrief.Compile().Invoke(null, client);
It allows me to only have to have one piece of code that understands the mapping from Client to ClientBrief, whether that code is running in the database or the client app. It all seems to work ok, except the query results all have an Id of 0.
How can I get the Id property (integer) properly populated in the query?
I've read a number of similar questions here but none of the suggested answers seem to work. (Changing the Ids to strings from integers is not an option.)
I have a hard time following your sample fully, Really the best way to dig in to this would be with a failing self-contained unit test.
Nonetheless, let's see if I can pull out the important bits.
In the transform, you have two areas where you are working with the id:
...
client = Database.Load(result.Id.ToString())
...
Id = this0.client.__document_id,
...
The result.Id in the first line and the Id = in the second line are expected to be integers.
The Database.Load() expects a string document key and that is also what you see in __document_id.
The confusion comes from Raven's documentation, code, and examples all use the terms id and key interchangeably, but this is only true when you use string identifiers. When you use non-string identifiers, such as ints or guids, the id may be 123, but the document key is still clients/123.
So try changing your transform so it translates:
...
client = Database.Load("clients/" + result.Id)
...
Id = int.Parse(this0.client.__document_id.Split("/")[1]),
...
... or whatever the c# equivalent linq form would be.
I'm trying to perform a very standard multi mapping query using Dapper, and I'm getting the following error. I also get another error occasionally when this seems to work, but I'm unable to reproduce it at the moment. I'll append it to this post if/when the first problem is solved.
Here is the query code:
const string storedProc = "dbo.GetStopsForRouteID";
var stops = conn.Query<RouteStop, MapLocation, RouteStop>(
storedProc, (stop, loc) =>
{
stop.Location = loc;
return stop;
}, new { RouteID = routeId }, commandType: CommandType.StoredProcedure);
In Dapper.cs on line 498:
var deserializer2 = (Func<IDataReader, TSecond>)info.OtherDeserializers[0];
info.OtherDeserializers is null which causes a NullReferenceException.
This is the guts of the stored procedure:
SELECT
RouteStops.StopID,
RouteStops.Name,
RouteStops.Description,
RouteStops.IsInbound,
RouteStops.Location.Lat as Latitude,
RouteStops.Location.Long as Longitude
FROM dbo.Routes
INNER JOIN dbo.StopsOnRoute ON
Routes.RouteID = StopsOnRoute.RouteID
INNER JOIN dbo.RouteStops ON
StopsOnRoute.StopID = RouteStops.StopID
WHERE Routes.RouteID = #RouteID
ORDER BY StopsOnRoute.SequenceNumber
I've had an extensive look at the dapper code but I can't find anything that seems out of place other than that TFirst's deserialiser isn't null, but TSecond's is. Could there be a problem when it creates TSecond's deserializer that leaves it as null?
Here are the types:
public class MapLocation
{
public double Latitude { get; set; }
public double Longitude { get; set; }
}
public class RouteStop {
public int StopID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public bool IsInbound { get; set; }
public MapLocation Location { get; set; }
}
Probably the main problem here is that you haven't told it how to "split"; try adding the parameter:
splitOn: "Latitude"
without that, as far as dapper can see there is no second result portion (it splits on Id by default).
I have a company that contains an address object. The SQL return is flat, and I'm tring to get Query<> to load all the objects.
cnn.Query<Company,Mailing,Physical,Company>("Sproc",
(org,mail,phy) =>
{
org.Mailing = mail;
org.Physical = phy;
return org;
},
new { ListOfPartyId = stringList }, null, true, commandTimeout: null,
commandType: CommandType.StoredProcedure, splitOn: "MailingId,PhyscialId").ToList();
I'm not sure if i have the SplitOn correct either. I'm getting the message:
When using the multi-mapping APIs ensure you set the splitOn param if
you have keys other than Id Parameter name: splitOn
Suggestions would be great.
The examples in the Test.cs are not what the code asks for as parameters for the queries. These need to be updated
for me this works perfect ... perhaps a typo?
I see PhyscialId which definitely looks like one.
class Company
{
public int Id { get; set; }
public string Name { get; set; }
public Mailing Mailing { get; set; }
public Physical Physical { get; set; }
}
class Mailing
{
public int MailingId { get; set; }
public string Name { get; set; }
}
class Physical
{
public int PhysicalId { get; set; }
public string Name { get; set; }
}
public void TestSOQuestion()
{
string sql = #"select 1 as Id, 'hi' as Name, 1 as MailingId,
'bob' as Name, 2 as PhysicalId, 'bill' as Name";
var item = connection.Query<Company, Mailing, Physical, Company>(sql,
(org, mail, phy) =>
{
org.Mailing = mail;
org.Physical = phy;
return org;
},
splitOn: "MailingId,PhysicalId").First();
item.Mailing.Name.IsEqualTo("bob");
item.Physical.Name.IsEqualTo("bill");
}