what is the correct syntax to write the second list? bookid and other fields are not recognizing
var bookssublist = from bookdetails in bookslist
join bookcategories in _context.BookCategories
on bookdetails.BookId equals bookcategories.BookId
where bookcategories.CategoryId==CategoryId
select new BookBasicInfo {
count = bookcount,
BookInfo = new List<BookInfo>()
{
BookId = bookdetails.BookId,
BookTitle = bookdetails.Title,
Images = bookdetails.ThumbnailImagePath,
PublishDate = bookdetails.PublishedDate,
AuthorList = bookdetails.BookAuthors.Select(q => q.Author.Author1).ToList(),
CategoryList =bookdetails.BookCategories.Select(q=>q.Category.CategoryName).ToList(),
}
};
You are using collection initializer in a wrong way. Actually, you forgot to pass an object of type BookInfo to the initializer.
BookInfo = new List<BookInfo>()
{
new BookInfo()
{
BookId = bookdetails.BookId,
BookTitle = bookdetails.Title,
Images = bookdetails.ThumbnailImagePath,
PublishDate = bookdetails.PublishedDate,
AuthorList = bookdetails.BookAuthors.Select(q => q.Author.Author1).ToList(),
CategoryList =bookdetails.BookCategories.Select(q=>q.Category.CategoryName).ToList()
}
}
Related
Hi I am changing career to computer programming. I am still in college. I have to change the following LINQ query from method syntax to query syntax. What gets me is the 2 steps process of the method query. First it gets a teamId and then it returns a list based on the context and using the teamId. I am confused about how to translate this to query method. Most of the questions are about going from query syntax to method.
Can someone Help?
public IEnumerable<TemplateView> GetTemplates(Guid userId, int languageId)
{
using (DigigateEntities context = new Models.DigigateEntities())
{
var teamId = context
.TeamMembers
.Include("Team")
.FirstOrDefault(c => c.UserId == userId)
.Team.Id;
return context
.TeamTemplates.Include("Template")
.Where(c => c.TeamId == teamId)
.Select(c => c.Template)
.Where(c => c.StatusId == 1/*Active*/)
.Select(k => new TemplateView
{
TemplateName = k.Name,
Id = k.Id,
IsCustom = k.Custom,
TypeId = k.TypeId,
TypeName = k.TemplateType.Description,
FileName = k.FileName,
TemplateImage = "test.png",
LanguageId = k.LanguageId,
LanguageName = k.Language.Name,
CreateDate = k.CreateDate
}).ToList();
}
}
The first one is pretty straight forward. I delayed the execution of the query until the end. Since you may get a null reference exception in your example accessing .FirstOrDefault().Team.Id;
var teamId = (from c in context.TeamMembers.Include("Team")
where c.UserId == userId
select c.Team.Id).FirstOrDefault();
This one you just need to use an into in order to continue your query statement
return (from c in context.TeamTemplates.Include("Template")
where c.TeamId == teamId
select c.Template into k
where k.StatusId == 1
select new TemplateView
{
TemplateName = k.Name,
Id = k.Id,
IsCustom = k.Custom,
TypeId = k.TypeId,
TypeName = k.TemplateType.Description,
FileName = k.FileName,
TemplateImage = "test.png",
LanguageId = k.LanguageId,
LanguageName = k.Language.Name,
CreateDate = k.CreateDate
}).ToList();
public IEnumerable<TemplateView> GetTemplates(Guid userId, int languageId)
{
using (DigigateEntities context = new Models.DigigateEntities())
{
var teamId = (from tm in context.TeamMembers.Include("Team")
where tm.UserId==userId
select tm.Id).FirstOrDefault();
IEnumerable<TemplateView> result = from k in (from tmp in context.TeamTemplates.Include("Template")
select tmp.Template)
where k.StatusId==1
select new
{
TemplateName = k.Name,
Id = k.Id,
IsCustom = k.Custom,
TypeId = k.TypeId,
TypeName = k.TemplateType.Description,
FileName = k.FileName,
TemplateImage = "test.png",
LanguageId = k.LanguageId,
LanguageName = k.Language.Name,
CreateDate = k.CreateDate
};
return result;
}
i have been finding problems related to the following code..Actually i want to select filtered records but it gives me 0 records. I have tried the following. Please Help me..
public static IEnumerable<PostModel> GetPostData(string cat)
{
var data = new LinqClassDataContext(); IEnumerable<PostModel> pm;
pm=data.PostTables.Where(Post => new PostModel
{ CategoryName= Post.CategoryName}.Equals(cat)).Select
(Post => new PostModel
{ PostID = (int)Post.PostID,
PostSubject = Post.PostSubject,
PostAuthor = Post.PostAuthor,
PostDate = Post.PostDate,
PostContent = Post.PostContent,
CategoryName = Post.CategoryName
});
}
Why your PostModel class object would be Equals string cat?
Maybe you meant:
data.PostTables.Where(Post => Post.CategoryName == cat)
Even though you overrided Equals method on PostModel I think you should use line I meantioned above because it is more obvious.
Also at the end of query you should call .ToList() method for initiating it. And you should dispose context after creating it in the method.
public static IEnumerable<PostModel> GetPostData(string cat)
{
var data = new LinqClassDataContext();
var pm = data.PostTables.Where(post => post.CategoryName == cat)
.Select(Post => new PostModel
{
PostID = (int)Post.PostID,
PostSubject = Post.PostSubject,
PostAuthor = Post.PostAuthor,
PostDate = Post.PostDate,
PostContent = Post.PostContent,
CategoryName = Post.CategoryName
})
.ToList();
data.Dispose();
return pm;
}
I try make table where i keep children-parent data. Ofc root of parents is "0" and here in table can by many roots. When i try make this work i got error.
Unable to create a constant value of type 'Projekty03.ViewsModels.ParagrafViewModel'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
public ViewResult Index()
{
List<ParagrafViewModel> _paragrafparent = new List<ParagrafViewModel>();
_paragrafparent.Add(new ParagrafViewModel { ParagrafID = 0, ParagrafNazwa = "Root" });
var _paragrafparent2 = from pr in paragrafRepository.All
orderby pr.ParagrafID
select new ParagrafViewModel
{
ParagrafID = pr.ParagrafID,
ParagrafNazwa = pr.ParagrafNazwa
};
var _paragrafparent3 = _paragrafparent.Concat(_paragrafparent2).AsEnumerable();
var paragraf = from par in paragrafRepository.All
join rodzic_p in _paragrafparent3
on par.ParagrafParent equals rodzic_p.ParagrafID
orderby par.ParagrafParent, par.ParagrafID
select new ParagrafViewModel
{
ParagrafID = par.ParagrafID,
ParagrafNazwa = par.ParagrafNazwa,
ParagrafParent = par.ParagrafParent,
ParagrafCzynny = par.ParagrafCzynny,
ParagrafWplyw = par.ParagrafWplyw,
ParagrafParentNazwa = rodzic_p.ParagrafNazwa
};
return View(paragraf);
}
I believe is sht wrong with my poor magic LINQ think. How resolve this ?
Ok here is a answer for my own question. Im sure is not a pretty solution but ...
public ViewResult Index()
{
List<ParagrafViewModel> _paragrafparent = new List<ParagrafViewModel>();
_paragrafparent.Add(new ParagrafViewModel { ParagrafID = 0, ParagrafNazwa = "Root", ParagrafCzynny=false, });
var _paragrafparent2 = from pr in paragrafRepository.AllIncluding(paragraf => paragraf.WniosekPodzial)
orderby pr.ParagrafID
select new ParagrafViewModel
{
ParagrafID = pr.ParagrafID,
ParagrafNazwa = pr.ParagrafNazwa,
ParagrafParent = pr.ParagrafParent,
ParagrafCzynny = pr.ParagrafCzynny,
ParagrafWplyw = pr.ParagrafWplyw,
WniosekPodzialNazwa = pr.WniosekPodzial.WniosekPodzialNazwa
};
var _paragrafparent3 = _paragrafparent.Concat(_paragrafparent2).AsEnumerable();
var paragrafModel = from par in _paragrafparent3
join rodzic_p in _paragrafparent3
on par.ParagrafParent equals rodzic_p.ParagrafID
orderby par.ParagrafParent, par.ParagrafID
select new ParagrafViewModel
{
ParagrafID = par.ParagrafID,
ParagrafNazwa = par.ParagrafNazwa,
ParagrafParent = par.ParagrafParent,
ParagrafCzynny = par.ParagrafCzynny,
ParagrafWplyw = par.ParagrafWplyw,
ParagrafParentNazwa = rodzic_p.ParagrafNazwa,
WniosekPodzialNazwa = par.WniosekPodzialNazwa
};
return View(paragrafModel);
}
I need to return a single instance of my viewmodel class from my repository in order to feed this into a strongly-typed view
In my repository, this works fine for a collection of viewmodel instances:
IEnumerable<PAWeb.Domain.Entities.Section> ISectionsRepository.GetSectionsByArea(int AreaId)
{
var _sections = from s in DataContext.Sections where s.AreaId == AreaId orderby s.Ordinal ascending select s;
return _sections.Select(x => new PAWeb.Domain.Entities.Section()
{
SectionId = x.SectionId,
Title = x.Title,
UrlTitle = x.UrlTitle,
NavTitle = x.NavTitle,
AreaId = x.AreaId,
Ordinal = x.Ordinal
}
);
}
But when I attempt to obtain a single entity, like this:
public PAWeb.Domain.Entities.Section GetSection(int SectionId)
{
var _section = from s in DataContext.Sections where s.SectionId == SectionId select s;
return _section.Select(x => new PAWeb.Domain.Entities.Section()
{
SectionId = x.SectionId,
Title = x.Title,
UrlTitle = x.UrlTitle,
NavTitle = x.NavTitle,
AreaId = x.AreaId,
Ordinal = x.Ordinal
}
);
}
I get
Error 1 Cannot implicitly convert type
'System.Linq.IQueryable<PAWeb.Domain.Entities.Section>' to
'PAWeb.Domain.Entities.Section'. An explicit conversion exists
(are you missing a cast?)"
This has got to be simple, but I'm new to c#, and I can't figure out the casting. I tried (PAWeb.Domain.Entities.Section) in various places, but no success. Can anyone help??
Your query is returning an IQueryable, which could have several items. For example, think of the difference between an Array or List of objects and a single object. It doesn't know how to convert the List to a single object, which one should it take? The first? The last?
You need to tell it specifically to only take one item.
e.g.
public PAWeb.Domain.Entities.Section GetSection(int SectionId)
{
var _section = from s in DataContext.Sections where s.SectionId == SectionId select s;
return _section.Select(x => new PAWeb.Domain.Entities.Section()
{
SectionId = x.SectionId,
Title = x.Title,
UrlTitle = x.UrlTitle,
NavTitle = x.NavTitle,
AreaId = x.AreaId,
Ordinal = x.Ordinal
}
).FirstOrDefault();
}
This will either return the first item, or null if there are no items that match your query. In your case that won't happen unless the table is empty since you don't have a where clause.
I am having trouble to return an IEnumerable and IList, I cant do it!
I am using EF 4 with POCOs
Here's the whole method:
//public IList<Genre> GetGenresByGame(int gameId)
public IEnumerable<Genre> GetGenresByGame(int gameId)
{
using(var ctx = new XContext())
{
var results =
from t0 in ctx.GameGenres
join t1 in ctx.GenreCultureDetails on t0.GenreId equals t1.GenreId
where t0.GameId == gameId && t1.CultureId == _cultureId
select new Genre
{
GenreId = t0.GenreId,
GenreName = t1.GenreName
};
return results.ToList();
}
}
I have tried different ways that I have found on the net.. but can't make it work!
Question 2:
I saw a screencast with Julie something, saying that "You should always return an ICollection" when using EF4.
Any thoughts about that ?
BR
EDIT:
When I load the page in Debug-mode i get these errors: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection. OR The entity or complex type 'XModel.Genre' cannot be constructed in a LINQ to Entities query.
Genre must not be a L2EF type. Try this:
public IEnumerable<Genre> GetGenresByGame(int gameId)
{
using(var ctx = new XContext())
{
var resultList =
from t0 in ctx.GameGenres
join t1 in ctx.GenreCultureDetails on t0.GenreId equals t1.GenreId
where t0.GameId == gameId && t1.CultureId == _cultureId
select new { t0.GenreId, t1.GenreName };
var genres = resultList.AsEnumerable().Select(o => new Genre
{
GenreId = o.GenreId,
GenreName = o.GenreName
});
return genres.ToList();
}
}
First an foremost if Genre is in the database you should select it? If you have FKs from Genre->GenreCultureDetails let me know and I can update the below, but from the looks of it you could do it like this:
using(var ctx = new XContext())
{
var results =
from g in ctx.Genre
join gcd in ctx.GenreCultureDetails on g.GenreId equals gcd.GenreId
where g.GameId == gameId && gcd.CultureId == _cultureId
select g;
return result.ToList();
}
Alternatively continue down your path select them into an annoynmous type, and then copy them. You can use select instead of convertall if you please.
IList<Genre> returnMe = Null;
using(var ctx = new XContext())
{
var results =
from t0 in ctx.GameGenres
join t1 in ctx.GenreCultureDetails on t0.GenreId equals t1.GenreId
where t0.GameId == gameId && t1.CultureId == _cultureId
select new
{
GenreId = t0.GenreId,
GenreName = t1.GenreName
};
returnMe = results.ToList().ConvertAll(x=>new Genre(){
GenreId = x.GenreId,
GenreName = x.GenreName
}
);
}
return returnMe;