I want this below class to return IList<>
Please tell me why it is not working
public IList<CheckBoxListInfo> GetLinks()
{
string linkName = string.Empty;
int linkId = 0;
using (var db = new brandconnectionsEntities())
{
var query = from s in db.BC_TabTable
select new
{
linkName = s.TabName,
linkId = s.TabId,
};
IList<CheckBoxListInfo> list = query.ToList() as IList<CheckBoxListInfo>;
return list;
}
}
Thanks
Ritz
You need to change your select statement to return CheckBoxListInfo objects.
e.g.
select new CheckBoxListInfo
{
LinkName = s.TabName,
LinkId = s.TabId,
};
At the moment it is returning an anonymous type.
It doesn't work because right now your query returns a sequence of an anonymous type defined by this expression:
select new
{
linkName = s.TabName,
linkId = s.TabId,
};
Instead, you need to select a new CheckBoxListInfo in your query, like this pseudo-code:
select new CheckBoxListInfo { LinkName = s.TabName, LinkId = s.TabId }
(I don't know how the CheckBoxListInfo API looks, so YMMV.
var query =(from s in db.BC_TabTable
select new CheckBoxListInfo
{
linkName= s.TabName,
linkId= s.TabId,
}).ToList();
Related
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()
}
}
I am trying to get a record from database using linq but it keep return no record
it is very basic sql statment
select * where productid ='12553'
however the following code does not return any result. Please advise. thx you
private static IEnumerable<ProductModel> GetAllProduct(string productId)
{
using (var dc = new TestEntities())
{
var result = (from a in dc.Products
where a.productid == productId
select new ProductModel
{
ProductId = a.productid,
Name = a.ProductName
});
return result.Distinct().ToList();
}
}
You don't need projection here:
using (var dc = new TestEntities())
{
var result = from a in dc.Products
where a.productid == productId
select a;
return result.Distinct().ToList();
}
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;
How to dynamically generate LINQ query:
int[] IDArray = {55, 36};
public IQueryable<ContactListView> FindAllContacts(int loggedUserID, int[] IDArray)
{
var result = (
from contact in db.Contacts
//Start of dynamic part...
where
contact.UserID == loggedUserID
foreach (var id in IDArray)
{
where contact.UserID == id
}
// End of dynamic part
orderby contact.ContactID descending
select new ContactListView
{
ContactID = contact.ContactID,
FirstName = contact.FirstName,
LastName = contact.LastName
});
return result;
}
Thanks,
Ile
Can't you just use Contains? I assume you want to generate a query that has an IN clause. There's an example of that here: Creating in queries with linq to sql.
int[] IDArray = {55, 36};
public IQueryable<ContactListView> FindAllContacts(int loggedUserID, int[] IDArray)
{
var result = (
from contact in db.Contacts
where contact.UserID == loggedUserID
&& IDArray.Contains( contact.UserID )
orderby contact.ContactID descending
select new ContactListView
{
ContactID = contact.ContactID,
FirstName = contact.FirstName,
LastName = contact.LastName
});
return result;
}
You probably want where IDArray.Contains(contact.UserID)
How can I project the row number onto the linq query result set.
Instead of say:
field1, field2, field3
field1, field2, field3
I would like:
1, field1, field2, field3
2, field1, field2, field3
Here is my attempt at this:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
int i = 1;
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select new ScoreWithRank()
{
Rank=i++,
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.ToList<ScoreWithRank>();
}
}
Unfortunately, the "Rank=i++" line throws the following compile-time exception:
"An expression tree may not contain an assignment operator"
Well, the easiest way would be to do it at the client side rather than the database side, and use the overload of Select which provides an index as well:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select new
{
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.AsEnumerable() // Client-side from here on
.Select((player, index) => new ScoreWithRank()
{
PlayerName = player.PlayerName,
PlayerScore = player.PlayerScore,
Rank = index + 1;
})
.ToList();
}
}
Ok, that did the trick. Thanks.
Here is my final code...
Server:
public List<Score> GetHighScores(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select s;
return query.ToList<Score>();
}
}
Client:
void hsc_LoadHighScoreCompleted(object sender, GetHighScoreCompletedEventArgs e)
{
ObservableCollection<Score> list = e.Result;
_listBox.ItemsSource = list.Select((player, index) => new ScoreWithRank()
{
PlayerName = player.PlayerName,
PlayerScore = player.PlayerScore,
Rank = index+=1
}).ToList();
}
You could also make just a slight adjustment to your original code to get it working. Word of caution, if you databind or access the object again, the Rank will increment each time. In those cases the top answer is better.
let Rank = i++
and
Rank.ToString()
Full code:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
int i = 1;
var query = from s in entities.Scores
let Rank = i++
where s.Game.Id == guid
orderby s.PlayerScore descending
select new ScoreWithRank()
{
Rank.ToString(),
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.ToList<ScoreWithRank>();
}
}
This solution worked for me.
http://www.dotnetfunda.com/articles/article1995-rownumber-simulation-in-linq.aspx
.Select((x, index) => new
{
SequentialNumber = index + 1
,FieldFoo = x.FieldFoo
}).ToList();
List<Emp> Lstemp = GetEmpList();
int Srno = 0;
var columns = from t in Lstemp
orderby t.Name
select new {
Row_number=++Srno,
EmpID = t.ID,
Name = t.Name,
City = t.City
};