Develop Reference

SelectListItem is empty, if statement inside method shows it to be filled

error message:
http://prntscr.com/qtlodf
method:
public IActionResult GroepsResultaten(int vakId, int groepId)
{
var studentenLijst = _context.Student.Join(_context.StudentGroep,
s => s.Id,
sg => sg.StudentId,
(s, sg) => new { Student = s, StudentGroep = sg })
.Where(x => x.StudentGroep.GroepId == groepId)
.Select(x => x.Student);
ViewBag.Studenten = new SelectList(studentenLijst, "Id", "Naam");
return View();
}
I've also tried this:
public IActionResult GroepsResultaten(int vakId, int groepId)
{
var studentInfo = _context.Student
.Select(s =>
new
{
s.Id,
Naam = string.IsNullOrEmpty(s.Tussenvoegsel)
? s.Voornaam + " " + s.Achternaam + " - " + s.Studentnummer
: s.Voornaam + " " + s.Tussenvoegsel + " " + s.Achternaam + " - " + s.Studentnummer,
forStudent = s.Studentnummer + "-" + s.Achternaam
});
ViewBag.Studenten = new SelectList(studentInfo, "Id", "Naam");
return View();
}
I'm a bit stuck at this. I want to return multiple input fields (I'm just testing with selectlist at the moment) for all students of group x, from there on I want to be able to grade students for the subject that's included in the view using get method. Because English isn't my first language I've included two screenshots to clarify what I mean.
clarification of what I want to achieve:
group view: http://prntscr.com/qtlrqd
wireframe of method view: http://prntscr.com/qtlswn
models:
public class Student
{
public int Id { get; set; }
[Required]
public string Voornaam { get; set; }
[Required]
public string Achternaam { get; set; }
public string Tussenvoegsel { get; set; }
public string Studentnummer { get; set; }
public List<Resultaat> Resultaten { get; set; }
public List<StudentGroep> Groepen { get; set; }
}
public class Groep
{
public int Id { get; set; }
[Required]
public string Naam { get; set; }
[Required]
public string Groepscode { get; set; }
public List<GroepVak> Vakken { get; set; }
public List<StudentGroep> Studenten { get; set; }
}
public class StudentGroep
{
public Student Student { get; set; }
public int StudentId { get; set; }
public Groep Groep { get; set; }
public int GroepId { get; set; }
}
I hope I've included enough information, I'm available on discord too if that makes it easier.

The problem is what the SelectList class returns. Because view side results that ViewBag.Studenten is null.
Also, you must make sure that the database query returns a value.

Using ViewData resulted in what I want, from here on I can hopefully figure out how to use it for posting grades for each student.
Method:
public IActionResult GroepsResultaten(int vakId, int groepId)
{
var studentenLijst = _context.Student.Join(_context.StudentGroep,
s => s.Id,
sg => sg.StudentId,
(s, sg) => new { Student = s, StudentGroep = sg })
.Where(x => x.StudentGroep.GroepId == groepId)
.Select(x => x.Student)
.ToList();
if (groepId >= 1)
{
ViewData["Studenten"] = studentenLijst.ToList();
}
//ViewBag.Studenten = new SelectList(studentenLijst, "Id", "Naam");
return View();
}
View:
#foreach (var item in ViewBag.Studenten)
{
#item.Voornaam;
<input type="number" />
}

Convert SQL to Linq with EF Core

I am using .NET Core 2.2, EF Core, C# and SQL Server 2017.
I am not able to translate the query I need to Linq.
This is the query I need to convert:
SELECT TOP 5
p.Id,
p.Title,
AVG(q.RatingValue) AvgRating
FROM Movies AS p
INNER JOIN Ratings AS q ON p.Id = q.MovieId
GROUP BY p.Id, p.Title
ORDER BY AvgRating DESC, p.Title ASC
The idea of the previous query is to get the Top 5 movies according to the Avg rating, ordering it by the highest average first, and in case of same average order alphabetically.
So far this is my query that makes the join, but then still missing: the group by, average, and ordering:
public class MovieRepository : IMovieRepository
{
private readonly MovieDbContext _moviesDbContext;
public MovieRepository(MovieDbContext moviesDbContext)
{
_moviesDbContext = moviesDbContext;
}
public IEnumerable<Movie> GetTopFive()
{
var result = _moviesDbContext.Movies.OrderByDescending(x => x.Id).Take(5).
Include(x => x.Ratings);
return result;
}
}
And these are the entities:
public class Movie
{
public int Id { get; set; }
public string Title { get; set; }
public int YearOfRelease { get; set; }
public string Genre { get; set; }
public int RunningTime { get; set; }
public IList<Rating> Ratings { get; set; }
}
public class Rating
{
public int Id { get; set; }
public int MovieId { get; set; }
public int UserId { get; set; }
public decimal RatingValue { get; set; }
}
I tried to use Linqer tool also to convert my query to Linq, but it was not working.
I will appreciate any help to convert that query to LINQ for the method "GetTopFive".
Thanks

Try this one -
var data = _moviesDbContext.Movies.Include(x => x.Ratings)
.Select(x => new {
Id = x.Id,
Title = x.Title,
Average = (int?)x.Ratings.Average(y => y.RatingValue)
}).OrderByDescending(x => x.Average).ThenBy(x => x.Title).Take(5).ToList();

Try as follows:
public IEnumerable<Movie> GetTopFive()
{
var result = _moviesDbContext.Ratings.GroupBy(r => r.MovieId).Select(group => new
{
MovieId = group.Key,
MovieTitle = group.Select(g => g.Movie.Title).FirstOrDefault(),
AvgRating = group.Average(g => g.RatingValue)
}).OrderByDescending(s => s.AvgRating).Take(5).ToList();
return result;
}
This will exclude the movies having no ratings.
But if you do as follows (as artista_14's answer):
public IEnumerable<Movie> GetTopFive()
{
var result = _moviesDbContext.Movies.GroupBy(x => new { x.Id, x.Title })
.Select(x => new {
Id = x.Key.Id,
Title = x.Key.Title,
Average = x.Average(y => y.Ratings.Sum(z => z.RatingValue))
}).OrderByDescending(x => x.Average).ThenBy(x => x.Title).Take(5).ToList();
return result;
}
this will include the movies having no ratings also.
Note: I see your Rating model class does not contain any Movie navigation property. Please add this as follows:
public class Rating
{
public int Id { get; set; }
public int MovieId { get; set; }
public int UserId { get; set; }
public decimal RatingValue { get; set; }
public Movie Movie { get; set; }
}

and finally this is the code working nicely:
var data = _moviesDbContext.Movies.Include(x => x.Ratings)
.Select(x => new MovieRating
{
Id = x.Id,
Title = x.Title,
Average = x.Ratings.Average(y => y.RatingValue)
}).OrderByDescending(x => x.Average).ThenBy(x => x.Title).Take(5).ToList();
return data;
The problem was creating an anonymous type in the select, so this line resolves the issue: .Select(x => new MovieRating
And this is the complete code for the method and the new class I have created to map the select fields with a concrete type:
public class MovieRepository : IMovieRepository
{
private readonly MovieDbContext _moviesDbContext;
public MovieRepository(MovieDbContext moviesDbContext)
{
_moviesDbContext = moviesDbContext;
}
public IEnumerable<Movie> GetAll()
{
return _moviesDbContext.Movies;
}
public IEnumerable<MovieRating> GetTopFive()
{
var result = _moviesDbContext.Movies.Include(x => x.Ratings)
.Select(x => new MovieRating
{
Id = x.Id,
Title = x.Title,
Average = x.Ratings.Average(y => y.RatingValue)
}).OrderByDescending(x => x.Average).ThenBy(x => x.Title).Take(5).ToList();
return result;
}
}
public class MovieRating
{
public int Id { get; set; }
public string Title { get; set; }
public decimal Average { get; set; }
}

LINQ query to find related data [duplicate]

This question already has answers here:
Projecting self referencing multi level Entities In Entity Framework 6
(2 answers)
Closed 5 years ago.
I got some help with my recursive product category tree view here on Stack Overflow before, and this is working:
Entity model:
public class ProductCategory
{
public int Id { get; set; }
public int SortOrder { get; set; }
public string Title { get; set; }
[ForeignKey(nameof(ParentCategory))]
public int? ParentId { get; set; }
public ProductCategory ParentCategory { get; set; } //nav.prop to parent
public ICollection<ProductCategory> Children { get; set; } //nav. prop to children
public List<ProductInCategory> ProductInCategory { get; set; }
}
Controller:
var categories = _context.ProductCategories.Include(e => e.Children).ToList();
var topLevelCategories = categories.Where(e => e.ParentId == null);
return View(topLevelCategories);
View:
#if (Model != null)
{
foreach (var item in Model)
{
<li>
#item.Title
<ul>
#Html.Partial("_CategoryRecursive.cshtml", item.Children)
</ul>
</li>
}
}
But when I tried to translate this setup to my viewmodel (and adding a property for counting products in each category, as well as a list of products without any category connection) ...:
Viewmodel:
public class ViewModelProductCategory
{
public int Id { get; set; }
public int? ParentId { get; set; }
public string Title { get; set; }
public int SortOrder { get; set; }
public string ProductCountInfo
{
get
{
return Products != null && Products.Any() ? Products.Count().ToString() : "0";
}
}
public ViewModelProductCategory ParentCategory { get; set; } // Nav.prop. to parent
public IEnumerable<ViewModelProductCategory> Children { get; set; } // Nav.prop. to children
public List<ViewModelProduct> Products { get; set; } // Products in this category
public List<ViewModelProduct> OrphanProducts { get; set; } // Products with no reference in ProductInCategory
}
Controller:
var VMCategories = _context.ProductCategories
.Include(e => e.Children)
.OrderBy(s => s.SortOrder)
.Where(r => r.ParentId == null) // only need root level categories in the View
.Select(v => new ViewModelProductCategory
{
Id = v.Id,
ParentId = v.ParentId,
Title = v.Title,
SortOrder = v.SortOrder,
// get products without a category:
OrphanProducts = v.ProductInCategory
.Where(o => !_context.ProductsInCategories.Any(pc => o.Id == pc.ProductId))
.Select(orph => new ViewModelProduct
{
Id = orph.Product.Id,
Title = orph.Product.Title,
Price = orph.Product.Price,
Info = orph.Product.Info,
SortOrder = orph.SortOrder
})
.OrderBy(s => s.SortOrder)
.ToList()
})
.ToList();
return View(VMCategories);
View:
#if (Model != null)
{
foreach (var item in Model)
{
<li>
#item.Title (#item.ProductCountInfo)
<ul>
#Html.Partial("_CategoryRecursive.cshtml", item.Children)
</ul>
</li>
}
}
... it won't work any more. The view does render, but it is just showing the root categories. It seems that my modified query won't get any of the children categories. When I inspect the query result, the Children property is null.
EDIT
I'm going with #Rainman's solution, and have changed my query .Select to include Children = v.Children,, and changing my viewmodel navigational properties thusly:
public ProductCategory ParentCategory { get; set; } //nav.prop to parent
public ICollection<ProductCategory> Children { get; set; } //nav. prop to children
I have also created the new viewmodel CategoryRecursiveModel and changed my view to this:
#model IEnumerable<MyStore.Models.ViewModels.ViewModelProductCategory>
<ul>
#if (Model != null)
{
foreach (var item in Model)
{
<li>
#item.Title (#item.ProductCountInfo)
<ul>
#Html.Partial("_CategoryRecursive.cshtml", new CategoryRecursiveModel
{
Children = item.Children.ToList();
})
</ul>
</li>
}
}
</ul>
Now I'm faced with InvalidOperationException, as the view is expecting an IEnumerable of ViewModelProductCategory, but receives CategoryRecursiveModel.

Because you are not selecting the Children for second query;
var VMCategories = _context.ProductCategories
.Include(e => e.Children)
.OrderBy(s => s.SortOrder)
.Where(r => r.ParentId == null) // only need root level categories in the View
.Select(v => new ViewModelProductCategory
{
Id = v.Id,
Children = v.Children, // Select it
ParentId = v.ParentId,
Title = v.Title,
SortOrder = v.SortOrder,
// get products without a category:
OrphanProducts = v.ProductInCategory
.Where(o => !_context.ProductsInCategories.Any(pc => o.Id == pc.ProductId))
.Select(orph => new ViewModelProduct
{
Id = orph.Product.Id,
Title = orph.Product.Title,
Price = orph.Product.Price,
Info = orph.Product.Info,
SortOrder = orph.SortOrder
})
.OrderBy(s => s.SortOrder)
.ToList()
})
.ToList();
public ProductCategory ParentCategory { get; set; } //nav.prop to parent
public ICollection<ProductCategory> Children { get; set; } //nav. prop to children
Also, navigation properties exist only for EF entities not ViewModelProductCategory model class or other classes.
EDIT
Create a model class for _CategoryRecursive view;
public class CategoryRecursiveModel
{
public List<ProductCategory> Children { get; set; }
}
And the change the main view;
#if (Model != null)
{
foreach (var item in Model)
{
<li>
#item.Title (#item.ProductCountInfo)
<ul>
#Html.Partial("_CategoryRecursive.cshtml", new CategoryRecursiveModel
{
Children = item.Children.ToList();
})
</ul>
</li>
}
}

ASP.NET MVC Edit CheckBoxList values in Database

I'm having trouble understanding how to retrieve and edit the DevId values from my CustomerDevice table in my database to the CheckBoxList based on the CustId value.
My Index Action Method for the CustomerDeviceController displays a list of Customers from my Customers table. I have an ActionLink labeled "Edit" that passes the CustId value to the CustomerDeviceController [HttpGet] Edit(int? id) Action Method which currently displays all CheckBoxListItem values from the Devices table. However, the CheckBoxList does not display the checked DevId values from the CustomerDevice table in the database to the CheckBoxList that pertain to the CustId, instead it displays a check for each of the CheckBoxList values.
The part that I'm having trouble understanding and figuring out, is how can I display the selected DevId values from the CustomerDevice table in my database to the CheckBoxList based on the CustId and then Edit/Update the modified CheckBoxListItems on the [HttpPost] Edit Action Method back to my CustomerDevice table in my database if need be.
Please see the following code below that I have so far.
Models
public class CheckBoxListItem
{
public int ID { get; set; }
public string Display { get; set; }
public bool IsChecked { get; set; }
}
public class Customer
{
public int CustId { get; set; }
public string CustDisplayName { get; set; }
public string CustFirstName { get; set; }
....
}
public class Device
{
public int DevId { get; set; }
public string DevType { get; set; }
}
public class CustomerDevice
{
public int CustId { get; set; }
public int DevId { get; set; }
public Customer Customer { get; set; }
public Device Device { get; set; }
}
ViewModels
public class CustomerDeviceFormViewModel
{
public int CustId { get; set; }
public string CustDisplayName { get; set; }
public List<CheckBoxListItem> Devices { get; set; }
}
CustomerDeviceController
public ActionResult Edit(int? id)
{
if (id == null)
{
return NotFound();
}
var customervm = new CustomerDeviceFormViewModel();
Customer customer = db.Customers.SingleOrDefault(c => c.CustId == id);
if (customer == null)
{
return NotFound();
}
customervm.CustId = customer.CustId;
customervm.CustDisplayName = customer.CustDisplayName;
// Retrieves list of Devices for CheckBoxList
var deviceList = db.Devices.ToList();
var checkBoxListItems = new List<CheckBoxListItem>();
foreach (var device in deviceList)
{
checkBoxListItems.Add(new CheckBoxListItem()
{
ID = device.DevId,
Display = device.DevType,
IsChecked = deviceList.Where(x => x.DevId == device.DevId).Any()
});
}
customervm.Devices = checkBoxListItems;
return View(customervm);
}
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(CustomerDeviceFormViewModel vmEdit)
{
if (ModelState.IsValid)
{
Customer customer = db.Customers.SingleOrDefault(c => c.CustId == vmEdit.CustId);
if (customer == null)
{
return NotFound();
}
foreach (var deviceId in vmEdit.Devices.Where(x => x.IsChecked).Select(x => x.ID))
{
var customerDevices = new CustomerDevice
{
CustId = vmEdit.CustId,
DevId = deviceId
};
db.Entry(customerDevices).State = EntityState.Modified;
}
db.SaveChanges();
return RedirectToAction("Index");
}
return View(vmEdit);
}
Edit.chtml
<div class="form-group">
Please select the Devices to assign to <b>#Html.DisplayFor(c => c.CustDisplayName)</b>
</div>
<div class="form-group">
#Html.EditorFor(x => x.Devices)
</div>
#Html.HiddenFor(c => c.CustId)
<div class="form-group">
<button type="submit" class="btn btn-primary">Submit</button>
</div>
Shared/EditorTemplate/CheckBoxListItem.chtml
<div class="checkbox">
<label>
#Html.HiddenFor(x => x.ID)
#Html.CheckBoxFor(x => x.IsChecked)
#Html.LabelFor(x => x.IsChecked, Model.Display)
</label>
<br />

Your code for setting the IsChecked value will always return true (your loop is basically say if the collection contains me (which of course it does) then set it to true).
You need to get the selected values for each Customer by reading the values from your CustomerDevice table
Customer customer = db.Customers.SingleOrDefault(c => c.CustId == id);
if (customer == null)
{
return NotFound();
}
// Get all devices
var deviceList = db.Devices.ToList();
// Get the selected device ID's for the customer
IEnumerable<int> selectedDevices = db.CustomerDevices
.Where(x => x.CustId == id).Select(x => x.DevId);
// Build view model
var model = new CustomerDeviceFormViewModel()
{
CustId = customer.CustId,
CustDisplayName = customer.CustDisplayName,
Devices = deviceList.Select(x => new CheckBoxListItem()
{
ID = x.DevId,
Display = x.DevType,
IsChecked = selectedDevices.Contains(x.DevId)
}).ToList()
};
return View(model);

Here's a snippet of Razor code that I've used:
foreach (SelectListItem p in Model.PositionList)
{
#Html.Raw(p.Text + "<input type=checkbox name=\"PositionIDs\" id=\"PositionIDs\" value=" + #p.Value + (Model.Positions != null && Model.Positions.Any(pos => pos.ScoreCardId == Convert.ToInt32(p.Value)) ? " checked />" : " />"));
}

You might want to have a look at the MvcCheckBoxList NuGet package:
https://www.nuget.org/packages/MvcCheckBoxList/
This makes doing some powerful stuff with a CheckBoxList much easier in MVC - and may be a better approach to fixing your CheckBox issues.

Issue Related to SelectMany function in LINQ

I have two tables in Database:
PostCalculationLine
PostCaluclationLineProduct
PostCalculationLineProduct(table2) contains Foriegn key of PostCalucationLineId(table1)
In C# code I have two different Models for these two tables as follows:
public class PostCalculationLine : BaseModel
{
public long Id{ get; set; }
public string Position { get; set; }
public virtual Order Order { get; set; }
public virtual Task Task { get; set; }
//some other properties go here
public virtual IList<PostCalculationLineProduct> PostCalculationLineProducts { get; set; }
}
and
public class PostCalculationLineProduct : BaseModel
{
public long Id {get;set;}
public string Description { get; set; }
//some other properties go here
}
Now in Entityframework code, I fetch data from PostCalculationLineProduct as follows:
PostCalculationLineRepository pclr = new PostCalculationLineRepository();
DataSourceResult dsrResult = pclr.Get()
.SelectMany(p => p.PostCalculationLineProducts)
.Where(c => c.Product.ProductType.Id == 1 && c.DeletedOn == null)
.Select(c => new HourGridViewModel()
{
Id = c.Id,
Date = c.From,
EmployeeName = c.Employee != null ?c.Employee.Name:string.Empty,
Description= c.Description,
ProductName = c.Product != null?c.Product.Name :string.Empty,
From = c.From,
To = c.Till,
Quantity = c.Amount,
LinkedTo = "OrderName",
Customer ="Customer"
PostCalculationLineId = ____________
})
.ToDataSourceResult(request);
In the above query I want to get PostCalculationLineId(from Table1) marked with underLine. How can I achieve this?
Thanks

You can use this overload of SelectMany to achieve this:-
DataSourceResult dsrResult = pclr.Get()
.SelectMany(p => p.PostCalculationLineProducts,
(PostCalculationLineProductObj,PostCalculationLineObj) =>
new { PostCalculationLineProductObj,PostCalculationLineObj })
.Where(c => c.PostCalculationLineProductObj.Product.ProductType.Id == 1
&& c.PostCalculationLineProductObj.DeletedOn == null)
.Select(c => new HourGridViewModel()
{
Id = c.PostCalculationLineProductObj.Id,
Date = c.PostCalculationLineProductObj.From,
//Other Columns here
PostCalculationLineId = c.PostCalculationLineObj.Id
};
This will flatten the PostCalculationLineProducts list and returns the flattened list combined with each PostCalculationLine element.