Develop Reference

One select list consisting of two classes

I have 3 classes
public class A
{
public decimal id {get; set;}
public virtual B? BNavigation {get; set;};
public virtual C? CNavigation {get; set;};
}
public class B
{
public int id {get; set;}
public string title {get; set;}
[...]
}
public class C
{
public int id {get; set;}
public string title {get; set;}
[...]
}
I try example above, string concatenation, tried to do it with LINQ.
I realized that I need to do this through an auxiliary class.
And i want to make SelectList by class A
Example:
ViewData["A"] = new SelectList( A,"Id", "BNavigation.title - CNavigation.title");
How can i do it ?

I want this post to be closed, because i found block of code which decide my problem
ViewBag.PackageId = db.Packages.Where(p => p.status == "A")
.Select(p => new SelectListItem
{
Text = p.u_package_id + "-" + p.package_nme,
Value = p.u_package_id.ToString()
});

Building includes map using EF Core

Hi I have a simple database, and what I am trying to do is build simple include maps as string using eager loading mechanism in EF CORE.
So in other words mu db models looks like:
And models that are supporting them:
public class StartTable
{
public int Id {get; set;}
public ICollection<TableA> TableA {get; set;}
public ICollection<TableB> TableA {get; set;}
}
public class TableA
{
public int Id {get; set;}
public StartTable StartTable {get; set;}
public int StartTableId {get; set;}
public TableAChild TableAChild {get; set;}
public int TableAChildId {get; set;}
public TableAB TableAB {get; set;}
public int TableABId {get; set;}
}
public class TableB
{
public int Id {get; set;}
public StartTable StartTable {get; set;}
public int StartTableId {get; set;}
public TableBChild TableBChild {get; set;}
public int TableBChildId {get; set;}
public TableAB TableAB {get; set;}
public int TableABId {get; set;}
}
public class TablAChild
{
public int Id {get; set;}
public TableA TableA {get; set;}
}
public class TableBChild
{
public int Id {get; set;}
public TableB TableB {get; set;}
}
public class TableAB
{
public int Id {get; set;}
public TableA TableA {get; set;}
public TableB TableB {get; set;}
}
I think relations are readible from models. Now I just want to create a map, that is I want to select start table and with include of all branches so final include path should looks like:
_context.StartTable.Include("StartTable.TableA.TableAChild")
_context.StartTable.Include("StartTable.TableA.TableAB")
_context.StartTable.Include("StartTable.TableB.TableBChild")
_context.StartTable.Include("StartTable.TableB.TableAB")
And If I type this manually it works, but this will grow a lot so I don't want to update this every time something will come up, I tried AutoInclute() in context on main table but it includes only 1 level down.
I thought I can create some sort of map function that looks like:
private static IEnumerable<string> BuildIncludeTree(DbContext context, Type type)
{
var entityAssemblyTypes = Assembly.GetExecutingAssembly().GetReferencedAssemblies().SelectMany(assembly => Assembly.Load(assembly).GetTypes());
void AddAssetByString(ref HashSet<string> navigation, List<string> createdPaths)
{
foreach (var path in createdPaths)
{
var splitPath = path.Split('.');
var relationNavigationNode = splitPath.Last();
var parentNavigationType = entityAssemblyTypes.FirstOrDefault(t => t.Name == relationNavigationNode);
if (parentNavigationType == null)
{
throw new ArgumentException($"Unknown type parent: {relationNavigationNode}");
}
var parentNodesProperties =
parentNavigationType.GetProperties().Where(prop => !prop.PropertyType.IsSimple() && !splitPath.Contains(prop.Name)).ToArray();
if (!parentNodesProperties.Any())
{
navigation.Add(path);
continue;
}
navigation.Add(path);
AddAssetByString(ref navigation, parentNodesProperties.Select(prop => $"{path}.{prop.Name}").ToList());
}
}
IEntityType entityType = context.Model.FindEntityType(type);
if (entityType == null) throw new ArgumentException($"Unknown entity type {type.Name}");
var navigationsByString = new HashSet<string>();
var relationsByString = entityType.GetNavigations().Select(nav => $"{type.Name}.{nav.Name}");
AddAssetByString(ref navigationsByString, relationsByString.ToList());
return new List<string>();
}
But problem here is relation to TableAB, I mean when I get to mapping this part function goes circular and creates map:
StartTable.TableA.TableAChild.TableB.StartTable.TableA ... and so on
Can this be prevented and what am I missing?
Can EF Core detect in some sort of way navigation downwards and upwards?
Or is there any other and simpler way to do that?

You can't Include all .There is already post about that here
Is there a way to Include() all with dbcontext?
But if correctly understand you can use Linq to make you code shorter like:
_context.StartTable.Include(x => x.TableA.TableAChild && x.TableA.TableAB && x. ....)
And in that case you will need to add entities you want to include in your class also you can use [NotMapped] attribute if you working direct with your class instead of dto. So in that way you can access the mapped entities direct from the class like class.TableAChild
+
public virtual TableAChild TableAChild { get; set; }
public virtual TableAB TableAB { get; set; }
Greetings and good luck

Deserializing Api Object with JSON.net

Let me explain my problem.
So I have JSON:
{"num":20, "meta":[{"id":312, "identif":{"type":true,"status":false}}}]}
I am currently grabbing the meta id field with:
var id = JsonConvert.DeserializeObject<typeObj>
(returnJSON(ApiUrl)).meta[0].id;
class to refrence:
class typeObj
{
public int num {get; set; }
public List<metatypes> meta {get; set;}
}
class metatypes
{
public int id {get; set;}
}
The issue doesn't lay here though. I am trying to get the indentif status element from meta.
I have tried putting a list in metatypes like:
class metatypes
{
public int id {get; set;}
public List<idtypes> identif {get; set;}
}
class idtypes
{
public bool type {get; set;}
public bool status {get; set;}
}
Calling it with:
var id = JsonConvert.DeserializeObject<typeObj>
(returnJSON(ApiUrl)).meta[0].identif[0].status;
But when I try this it returns
'Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1'
Looked around and couldn't find a direct solution to my problem.

You have an incorrect json for the desired structure:
Given classes:
class typeObj
{
public int num {get; set; }
public List<metatypes> meta {get; set;}
}
class metatypes
{
public int id {get; set;}
public List<idtypes> identif {get; set;}
}
class idtypes
{
public bool type {get; set;}
public bool status {get; set;}
}
Your json should look like (identif must be an array): (.NET Fiddle)
{"num":20, "meta":[{"id":312, "identif":[{"type":true,"status":false}]}]}
For the json in question your classes should be like this: (.NET Fiddle)
class typeObj
{
public int num {get; set; }
public List<metatypes> meta {get; set;}
}
class metatypes
{
public int id {get; set;}
public idtypes identif {get; set;}
}
class idtypes
{
public bool type {get; set;}
public bool status {get; set;}
}

Entity framework one to many

I am using Entity Framework and have the following classes
class Student
{
[Key]
public virtual int StudentID {get; set;}
public virtual string StudentName {get; set;}
public virtual ICollection<Note> Notes {get; set;}
}
class Note
{
[Key]
public virtual int NoteID {get; set;}
public virtual int StudentID {get; set;}
public virtual string Message {get; set;}
}
class StudentDBContext:DbContext
{
public DbSet<Student> Students { get; set; }
public DbSet<Note> Notes { get; set; }
}
So to summarize, I have a class of students who can each have many notes. Now, I want to use Linq to retrieve and display all the notes for a particular student. So I try
using (StudentDBContext a = new StudentDBContext())
{
var b = from c in a.Student
where c.StudentID == 1001
select c;
var currStudent = b.FirstOrDefault();
Console.WriteLine(currStudent.StudentName);
//display all the messages of the current student
foreach (var currNote in currStudent.Notes)
Console.WriteLine(currNote.Message);
}
In the above code, my foreach block always fails because Student.Notes is always null. Am I missing some step in initializing Student.Notes and populating it from the database?

Your class Student and Note should be public.
The following code runs:
class Program {
static void Main(string[] args) {
using ( StudentDBContext efc = new StudentDBContext()) {
foreach (var v in efc.Students) {
Console.WriteLine("{0}", v.StudentName);
foreach (var vv in v.Notes) {
Console.WriteLine(" {0}", vv.Message);
}
}
}
}
}
public class Student {
public Student() {
//Notes = new List<Note>();
}
[Key]
public int StudentID {get; set;}
public virtual string StudentName {get; set;}
public virtual ICollection<Note> Notes {get; set;}
}
public class Note {
[Key]
public int NoteID {get; set;}
public int StudentID {get; set;}
public string Message {get; set;}
}
class StudentDBContext:DbContext {
public DbSet<Student> Students { get; set; }
public DbSet<Note> Notes { get; set; }
}

try this:
using (StudentDBContext a = new StudentDBContext())
{
var b = ((from c in a.Student
join b in a.Notes on b.StudentId equals c.StudentId into sNotes
from notes in sNotes.DefaultIfEmpty()
where c.StudentId==1001
select c).SingleOrDefault();
if (b != null )
...
}
Be aware of the fact that Entity Framework will do a lazy load of your data. So if you don't do something to populate it then you will not get it. There are other ways of doing it but among other things this query clearly documents that you are wanting both the student and notes.

This shouldn't be virtual.
public virtual NoteID {get; set;}
It should be an integer:
public int NoteID {get; set;}

Constraints and implicite operators

I have three classes A,B and C,
some properties are in all three classes, some not
public class A
{
public string Firstname {get; set;}
public string Lastname {get; set;}
public int ID {get; set;}
public int xxx {get; set} // only in class A
public int yyy{get; set} // only in class A
...
}
public class B
{
public string Firstname {get; set;}
public string Lastname {get; set;}
public int ID {get; set;}
public int aaa {get; set} // only in class B
public int bbb {get; set} // only in class B
...
}
public class C
{
public string Firstname {get; set;}
public string Lastname {get; set;}
public int ID {get; set;}
public int kkk {get; set} // only in class C
public int ppp {get; set} // only in class C
...
}
I want to call the Execute method of class XYZ ...
public class XYZ
{
public override Execute<T>() where T: Generic_T, new()
{
T abc = new T();
...
Debug.WriteLine(abc.Firstname + ”, “ + abc.Lastname + “, “ + abc.ID);
}
}
... with all three classes,like:
XYZ x1 = new XYZ();
XYZ.Execute<A>();
XYZ x2 = new XYZ();
XYZ.Execute<B>();
XYZ x3 = new XYZ();
XYZ.Execute<C>();
My idea doesn’t work:
public class Generic_T
{
public static implicit operator A(Generic_T x)
{
return (A)x.MemberwiseClone();
}
}
Where is the mistake?
Thanks in advance!

Mistakes:
What is CloneMemberwise() ?
If you meant MemberwiseClone(), you can't call it there. It is a protected member.
You cannot call properties on a type. Here: T.Firstname, T.Lastname, etc.
It is Debug, not Degub.
You do not pass a value/reference in to the Execute method.
Neither A, B or C derives from Generic_T, so the constraint on the Execute method will fail.
Class names do not end with (). You had class A() which I re-edited already.
A or any class cannot be automagically converted to Generic_T.
You should be using inheritance, I suspect Generic_T should be a base class.
You do not have a specific question
Possible suggestion:
public abstract class Generic_T
{
public string Firstname {get; set;}
public string Lastname {get; set;}
public int ID {get; set;}
}
public class A : Generic_T
{
public int xxx {get; set} // only in class A
public int yyy{get; set} // only in class A
...
}
public class B : Generic_T
{
public int aaa {get; set} // only in class B
public int bbb {get; set} // only in class B
...
}
public class C : Generic_T
{
public int kkk {get; set} // only in class C
public int ppp {get; set} // only in class C
...
}
Also there is not reason to convert any of the derived classes to Generic_T as they as an instance of Generic_T already.
All of this information is normally explained in most introductory texts for C#/.NET. Failure to understand them, will make your life miserable.

Don't know why do you need Generic_T in your code.
To force Execute work you need to implement following interface
interface IFoo
{
int ID {get; set;}
string LastName {get; set;}
string FirstName {get; set;}
}
Then your execute method will look like this:
public override Execute<T>(T obj) where T: new(), IFoo
{
Debug.WriteLine(obj.Firstname + ”, “ + obj.Lastname + “, “ + obj.ID);
}