public class Product
{
public int Id{get;set;}
public int UserId{get;set;}
public Users User{get;set;}
}
I have set the Users to Product's relative:
b.HasOne("User").WithMany().HasForeignKey("UserID");
When I use entityframework to get the list of products.
The User is returned null, why?
There is a value in User table and the UserId is right in Product Table.
var list = _context.Products.AsQueryable();
the items in list has the User=null.
You need to Include the entity you're looking for. For example, let's suppose I have the following context.
AppDbContext.cs
public class AppDbContext : DbContext
{
public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
{
}
public DbSet<Notification> Notifications { get; set; }
public DbSet<Offer> Offers { get; set; }
}
Notification.cs
public class Notification
{
public int Id { get; set; }
public string Title { get; set; }
public int? OfferId { get; set; }
public virtual Offer Offer { get; set; }
}
If you want to use the Offer entity from Notification, you need to use the following statement:
context.Notifications.Include(n=> n.Offers).ToList();
// Your code goes here
In your situation:
var list = _context.Products.Include(p=> p.User).AsQueryable();
You have to explicitly ask to include the users in the returned list.
_context.Products.Include(p => p.Users).AsQueryable();
Related
I have a many-to-many relationship between User(Contributor) and TaskType. I want to assign to a variable only TaskTypes that have the current user among their contributors. Obviously, I can somehow do this using the functionality of the Entity Framework. But how? I use asp.net core 3.
Below I try unsuccessfully to do it:
public IQueryable<TaskType> ContributedTaskTypes
{
get
{
// This code doesn't work!
return _dbContext.TaskTypes.Where(t => t.Contributors.Contains(c => c.UserId == CurrentUserId));
}
}
Below are definitions of all models involved in this relationship:
public class TaskType
{
public int Id { get; set; }
public string UserId { get; set; }
public ApplicationUser ApplicationUser { get; set; }
public virtual List<Contribution> Contributors { get; set; }
}
public class Contribution
{
public int Id { get; set; }
public string UserId { get; set; }
public ApplicationUser ApplicationUser { get; set; }
public int TaskTypeId { get; set; }
public TaskType TaskType { get; set; }
}
public class ApplicationUser : IdentityUser
{
public virtual List<Contribution> ContributedToTaskTypes { get; set; }
}
For those queries it is always easiest to do queries where you can dot to the result.
Here is the query with sql-like syntax
from row in _dbContext.Contribution
where row.UserId == CurrentUserId
select row.TaskType
By selecting row.TaskType instead of just row you get it correct entity.
Is that Contributors property retrieved correctly from DB? if it is not you must call Include() method to load/refer relational referenced entities
_dbContext.TaskTypes.Include(p=>p.Contributors).Where(..
more: https://learn.microsoft.com/en-us/ef/core/querying/related-data
In Addition, if EF Core Table Relation is not correctly defined, you should follow
this instruction: https://www.entityframeworktutorial.net/efcore/configure-many-to-many-relationship-in-ef-core.aspx
I have the following controller which is supposed to create a new object in the database:
[HttpPost]
public ActionResult<Panels> CreateNewPanel(Panels panel)
{
_context.Panels.Add(panel);
_context.SaveChanges();
return CreatedAtAction(nameof(GetPanelById), new { id = panel.ID }, panel);
}
It is receiving some JSON data, example:
{
"desc": "test5",
"frame": 2,
"aC240v": false
}
Which maps to the following model:
public class Panels
{
public int ID { get; set; }
public string Desc { get; set; }
public PanelFrames Frame { get; set; }
public bool AC240v { get; set; }
}
It works for the most part if "frame" isn't set, but if it is set to an integer like the code above it fails because it is type PanelFrames not an integer.
PanelFrames is another model that has a one to many relationship with Panels, each Panel can have only one PanelFrame so in the database this is recorded as simply an integer, the PanelFrames ID.
How do I reconcile this so that the integer (which is the PanelFrame ID) get's passed through the API and recorded in the database. The MS documentation doesn't seem to cover this, though it seems like it would be a pretty common occurrence, so I must not be understanding something, or doing something very wrong.
If you use EF Core one-to-many relationships and save the principle entity(PanelFrames) id,you just need to add a foreign key for your navigation property in your Panel model.Refer to my below demo:
1.Models
public class Panels
{
[Key]
public int ID { get; set; }
public string Desc { get; set; }
public int FrameID { get; set; }
[ForeignKey("FrameID")]
public PanelFrames Frame { get; set; }
public bool AC240v { get; set; }
}
public class PanelFrames
{
[Key]
public int PanelFramesID { get; set; }
public string Name { get; set; }
public List<Panels> Panels { get; set; }
}
2.In my case, I pass json data using postman, so I need to use [FromBody] on action parameters.
json:
{
"desc": "test5",
"frameid": 2,
"aC240v": false
}
Action:
[HttpPost]
public ActionResult<Panels> CreateNewPanel([FromBody]Panels panel)
Then a new Panel with FrameId would be added into database.
3.If you need to get panels with their Frame, just use Include method in action like
using Microsoft.EntityFrameworkCore;//Add necessary namespaces before
//...
var panels= _context.Panels
.Include(p => p.Frame)
.ToList();
I am trying to determine what would be the smartest way to accomplish this. I may be way way overthinking what I am trying to do, but here goes.
I have the following entities, simplified
public class Meet
{
public int Id { get; set; }
//various properties
public List<MeetComp> Competitors { get; set; }
}
public class Competitor
{
public int Id { get; set; }
// various properties
public List<MeetComp> Meets { get; set; }
[ForeignKey("GymManager")]
public int GymManagerId { get; set; }
public GymManager GymManager { get; set; }
}
public class GymManager
{
public int Id { get; set; }
//various properties
public List<Competitor> Competitors { get; set; }
}
public class MeetComp
{
public int Id { get; set; }
[ForeignKey("Competitor")]
public int CompetitorId { get; set; }
public Competitor Competitor { get; set; }
[ForeignKey("Meet")]
public int MeetId { get; set; }
public Meet Meet { get; set; }
}
So I am creating a razor page where I get a specific Gymmanager and load all the related competitors to display in a list, which I have working just fine.
However I need another list (on the same page) of the related competitors of the Gymmanager but also who have an entry in the "MeetComp" table by a specific meetid. So List #1 is all of my Competitors and List #2 is all of my Comptetitors that are registered for that Meet.
Would it be smarter to have EF pull the data I get the data the first time with a ThenInclude()? Then I write some logic to determine if they get added to list #2? or should I make another trip to the Database? Then if I do make another trip to the database is there an easy to way to query for the List of CompId's I already have?
So here's what I ended up doing is making another trip to the DB.
public async Task<IActionResult> GetRegisteredComps(List<int> Comps, int meetid)
{
if(Comps.Count == 0)
{
return Ok();
}
if(meetid == 0)
{
return BadRequest();
}
var query = _context.MeetsComps.Include(c => c.Competitor)
.AsQueryable();
query = query.Where(c => c.MeetId == meetid);
query = query.Where(c => Comps.Contains(c.CompetitorId));
var results = await query.ToListAsync();
return Ok(results);
}
I am new to Web Api and just trying to learn by playing with different examples. I am completely stuck on trying to write a Get request to return a complex type. I have 3 entities, 1 of the entities has a list of another entity, So I am trying to figure out how to return the data from within both.
I looked at some examples on stack overflow, that showed to use the .Include linq statement, but when I try that, I am getting compiler errors (type argument cannot be inferred.
Basically, I have a class of Players, Teams and Specialties. Once I get this working, I am planning on writing an angular project. The specialties table is a multiselect for a given player.
Here is what I have written so far
public class Player
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public int JerseyNo { get; set; }
public DateTime DateAquired { get; set; }
public string Bio { get; set; }
[ForeignKey("TeamID")]
public virtual Team Team { get; set; }
public virtual IEnumerable<Specialty> Specialites { get; set; }
}
public class Specialty
{
public int Id { get; set; }
public string Speciality { get; set; }
public virtual Player Player { get; set; }
}
public class Team
{
public int Id { get; set; }
public string TeamName { get; set; }
public virtual Player Player { get; set; }
}
public class dbContext :DbContext
{
public DbSet<Player> Players { get; set; }
public DbSet<Team> Teams { get; set; }
public DbSet<Specialty> Specialties { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder builder)
{
builder.UseSqlServer(#"Server=(localdb)\mssqllocaldb;Database=Test;Trusted_Connection=True;");
}
}
When I created the database using migrations, it looks how I want it to, but cannot figure out Web Api's joins to get the data from my specialties table. The .Include cannot recognize any value I enter as parameters
private dbContext db = new dbContext();
// GET: api/values
[HttpGet]
public IEnumerable<Player> Get()
{
var teams = db.
Players
.Include("Specialties")
.Select(p=> new Player
Looks like this an Entity Framework question.
Try if you can get this to work, for debugging purpose:
var teams = db.Players.ToList();
foreach (var player in teams)
{
// Force lazy loading of Specialities property
player.Specialities.ToList();
}
If this doesn't work, it looks like EF cannot figure out the mapping to the database.
I have a table in SqlServerDatabase. Table name is User(Id,Name,Paswd) and Im using automapper in Mvc4. Now i want only specific fields or 2 fields from the table instead of whole table, using automapper.how to do??
basically if the 2 objects have the same fields as in the little example
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public string Paswd { get; set; }
}
public class UserDto
{
public int Id { get; set; }
public string Name { get; set; }
public string Paswd { get; set; }
}
You just have to ignore the field
Mapper.CreateMap<User, UserDto>()
.ForMember(o => o.Paswd, m => m.Ignore());
You can find a lot of usefull example and features here
Automapepr Wiki