I have a recipe table that has a related ingredients table
on one to many basis.
How do I select using Linq ingredients
that have a ingredientName column and it should contain
a specified word.
This is what I tried.
IQueryable<OurRecipes.Domain.Linq2Sql.Recipe> recipes = _dbctx.Recipes.AsQueryable();
foreach (string word in searchdata.Keywords)
{
recipes = recipes.Where(r => r.RecipeTitle.Contains(word));
recipes = recipes.Where(r => r.Ingredients.Where(i => i.IngredientName.Contains(word)));
}
I get cannot convert type 'etc' to bool error.
Any ideas
Malcolm
The error lies here:
recipes = recipes.Where(r => r.Ingredients.Where(i => i.IngredientName.Contains(word)));
The condition inside Where must return a boolean, in this case, the r.Ingredients.Where(i => i.IngredientName.Contains(word)) will not return a boolean, and hence the error.
This is how you can fix the problem:
recipes = recipes.Where(i => i.Ingredients.Any(row=>row.IngredientName.Contains(word)));
r.Ingredients.Where(i => i.IngredientName.Contains(word)));
replace with
r.Ingredients.Any(i => i.IngredientName.Contains(word)));
Btw, I like SQL like syntax more as it more netural. The same:
from r in _dbctx.Recipes
where r.Ingredients.Any(i => i.IngredientName.Contains(word)));
select r;
This will select all recipies that has ingredients with name contains word.
Related
trying to convert a query which has 2 levels of where in clauses to linq and getting some errors. Can anybody help me on this?
Original Query:
select id
from student
where suId
in (select suId
from subjects
where cid
in (select id
from chapters
where chapter='C203'))
LINQ query:
var query = (from s in dc.students
let subs = (from su in dc.subjects
where su.cid == Convert.ToInt32(from c in dc.Chapters
where c.chapter == 'Ç203'
select c.id) //Single chapter id will be returned
select su.suid)
where subs.Contains(s.sid)
select s.id).ToArray();
Am getting below 2 errors while compiling app
'System.Linq.IQueryable' does not contain a definition for 'Contains' and the best extension method overload 'System.Linq.ParallelEnumerable.Contains(System.Linq.ParallelQuery, TSource)' has some invalid arguments
Instance argument: cannot convert from 'System.Linq.IQueryable' to 'System.Linq.ParallelQuery'
Since Linq is lazy-loading everything you don't need to cram everything into a single statement; you can do something like this:
var chapterIds = dc.Chapters
.Where(c => c.Chapter == "C023")
.Select(c => c.Id);
var subjectIds = dc.Subjects
.Where(s => chapterIds.Contains(s.Cid))
.Select(s => s.Suid);
var students = dc.Students
.Where(s => subjectIds.Contains(s.Suid))
.Select(s => s.Sid)
.ToArray();
This way you can debug each subquery by looking at what it returns.
However, looking at your original select you can rewrite the whole thing as a Join and get rid of the bugging issue:
var students = dc.Chapters.Where(c => c.Chapter == "C023")
.Join(dc.Subjects,
c => c.Id,
s => s.Cid,
(chapter, subject) => subject)
.Join(dc.Students,
subj => subj.Suid,
student => student.Suid,
(subj, st) => st.Sid)
.ToArray();
I'm trying to add a column to the following LINQ expression. I want the column to contain a string concatenation of a text value in a many table called WasteItems. The join would be on "Waste.WasteId = WasteItem.WasteId". My problem is I need to display in a single dynamic column a string such as "EW (5); EX (3)" if there was 8 records in WasteItem and the column containing the 2 character string was called WasteItem.EWC. Hope that makes sense, there must be an efficient way since I realise LINQ is very powerfull. I'm new to it and not sure how to start or go about this:
return from waste in this._db.Wastes
where (from u in _db.UsersToSites.Where(p => p.UserId == userId && p.SystemTypeId == SystemType.W)
select u.SiteId)
.Contains(waste.SiteId)
orderby waste.Entered descending select waste;
THANKS IN ADVANCE
Something like this should do:
wastes.GroupJoin(db.WasteItems, w => w.WastId, wi => wi.WasteId, (w,wi) => new { w, wi })
.AsEnumerable()
.Select(x => new
{
x.w.Name,
Items = string.Join(", ", x.wi.GroupBy(wi => wi.EWC).Select(g => string.Format("{0} ({1})", g.Key, g.Count())))
})
Where wastes is the result from your query. The AsEnumerable() is necessary because Entity Framework can not handle string.Join, so that part must be dealt with in memory.
I could not check the syntax, obviously, but at least it may show you the way to go.
How should I structure a Linq query to return a List or Ienumerable of the most popular Tags in my db (I am using EF4.1 by the way).
Currently I have:
var tagsListing = db.Tags
.GroupBy(q => q.Name)
.OrderByDescending(gp => gp.Count())
.Take(5)
.Select();
I think I am part of the way there, but I am unsure of how to structure the Select statement...
Your Select call could look like this:
.Select(gp => gp.Key)
That will give you an IEnumerable<string> of your most popular tags (assuming that Name is a string).
Assuming you want the name and the count, just:
.Select(g => new { Name = g.Key, Count = g.Count() });
EDIT: If you want the complete tags as well, you could use:
.Select(g => new { Tags = g, Count = g.Count() })
which would give you a sequence of groups of tags, all with the same name within a group. Or you might only want the first tag within each group, e.g.
.Select(g => g.First())
It's not clear what a Tag consists of, or what exactly you want in the results.
You've written a perfectly workable query and do not need to call .Select
IQueryable<IGrouping<string, Tag>> tagsListing = db.Tags
.GroupBy(q => q.Name)
.OrderByDescending(gp => gp.Count())
.Take(5);
List<IGrouping<string, Tag>> results = tagListing.ToList();
You probably want to select the names like this:
.Select(gp => gp.Key);
I have this code
var contacts = dr.mktDoctorContacts
.GroupBy(x => x.ContactType)
.Select(zb => new
{
Key = zb.Key,
GroupWiseContacts = zb.Select(x => x.Contact).ToList()
})
.ToDictionary<string,List<string>>(y => y.Key, y => y.GroupWiseContacts)
I don't know what is wrong with this code.
Compile time error msg says:System.Generic.IEnumerable does not contain definition of and best extension method overloads has some invalid arguments. i can see only two overloads of ToDictionary Method in my visual studio tooltip sort of documentation whereas i have come across more than two overloads of ToDictionary on the web
Edit Here is exact Error message at compile time
Error 13 'System.Collections.Generic.IEnumerable<AnonymousType#1>'
does not contain a definition for
'ToDictionary' and the best extension
method overload
'System.Linq.Enumerable.ToDictionary<TSource,TKey>(System.Collections.Generic.IEnumerable<TSource>,
System.Func<TSource,TKey>,
System.Collections.Generic.IEqualityComparer<TKey>)'
has some invalid arguments
The compiler message makes the error clear: There is no method ToDictionary which can accept the arguments and types specified.
The mistake here is in specifying the type arguments on ToDictionary. The MSDN documentation defines the extension method as ToDictionary<TKey, TSource>. The source in your example is IEnumerable<AnonymousType#1>, but you have specified a type of List<string>.
To correct the error, omit the type arguments; the compiler will infer the correct types. You can additionally combine the Select and ToDictionary transformations into a single statement:
var contacts = dr.mktDoctorContacts
.GroupBy(x => x.ContactType)
.ToDictionary(
y => y.Key,
y => y.Select(x => x.Contact).ToList());
Rewrote your code (and added .AsEnumerable()):
var dictionary = dr.mktDoctorContacts
.GroupBy(x => x.ContactType)
.AsEnumerable()
.ToDictionary(
i => i.Key,
i => i.Select(x => x.Contact).ToList()
)
);
Don't run that group operation in the database, it'll cause the elements of each group to be fetched in separate roundtrips.
ILookup<string, string> contacts = dr.mktDoctorContacts
.ToLookup<Contact, string, string>(x => x.ContactType, x => x.Contact);
I am trying to run a query where I get the name of locations and the number of items in that location. So if i have a program that contains 3 locations I want to know how many programs are in that location..I need to use this with a lambda expression or linq to entities.
return Repository.Find(x => x.Location.Name.Count())...clearly missing something here.
we'll just assume I have a Program entity with ProgramID, ProgramName, LocationName...need to know how many programs are in at a location
You can do it like this:
return repository.Count(x => x.Location == "SomeLocation");
Do you want to know the counts for all locations at once?
var locCounts = Repository.GroupBy(prog => prog.Location.Name).ToLookup(g => g.key, g => g.Count());
if you will repositoryPattern, use this code
Clients.Where(p => p.DateOfArrival >= DateTime.Now.AddDays(-3) && p.DateOfArrival <= DateTime.Now.AddDays(3)).Select(p => p.ID).Count()
Repository Pattern