I get LINQ to Entities Int32 ToInt32(System.String) when convert.i tried int.Parse() , SqlFunction and EdmFunction but the problem still going on.
Exception:
System.NotSupportedException: LINQ to Entities does not recognize the method 'Int32 ToInt32(System.String)' method, and this method cannot be translated into a store expression
Code:
try
{
ModelEntities me = new ModelEntities();
var query = from p in me.Products
join c in me.ProductCategories
on Convert.ToInt32(p.CategoryId) equals c.CategoryId
select new
{
p.ProductTitle,
c.CategoryName
};
rptProducts.DataSource = query;
rptProducts.DataBind();
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
You cannot use Convert.ToInt32 inside your linq query. Linq has its own syntax and does not recognize external methods.
Either you have to extract the variable you are looking for to C#, convert it, and use it as a variable in another query. Or you could make both categoryIDs ints, if you have access to the database. It makes sense that similar fields like those should be of the same type.
Hope that helps!
I suggest converting c.CategoryId to string like this
var query = from p in me.Products
from c in me.ProductCategories
let categoryId = me.ProductCategories.Take(1).Select(x => c.CategoryId).Cast<string>().FirstOrDefault()
where p.CategoryId == categoryId
select new
{
p.ProductTitle,
c.CategoryName
};
Related
I have the following entity code where i want to return a formatted string based on a custom a function that return a string:
var query =
from a in db.Authors
join b in db.Books
on a.id equals b.atuhorId into ab
from item in ab.DefaultIfEmpty()
select new
{
id = a.id,
authorName= a.name,
bookName = b.name,
formatted_book = item.id != null ? model.getFormatedBook(item.id) : "N/A",
},
};
But i got an error like mentioned in my post title.
Is there a cast that i can put inside my entity code for the getFormatedBook(item.id) ? I tried getFormatedBook(item.id).ToString() but with no success
Thanks
LINQ to Entity is unable to call outside methods as a part of a query. Take a look at this answer: https://stackoverflow.com/a/12641286/1202275 for possible workarounds.
I have a method:
public List<Timetable> getTimetableTableForRegion(String id) {
List<Timetable> timetables;
TypedQuery<Timetable> query = em_read.createQuery("SELECT ..stuff.. where R.id = :id", Timetable.class).setParameter("id", Long.parseLong(id));
timetables = query.getResultList();
return timetables;
}
which returns this:
so, what am I missing in order to return a list of Timetable's?
ok, so, ..stuff.. part of my JPQL contained an inner join to other table. Even through in SELECT there were selected fields just from one table, which was used as type - Timetable, Eclipslink was unable to determine if this fields are part of that entity and instead of returning list of defined entity returned list of Object[].
So in conclusion: Use #OneToMany/#ManyToOne mappings (or flat table design) and query just for ONE table in your JPQL to be able to typize returned entities.
Not sure it might be something is looking for, but I had similar problem and converted Vector to ArrayList like this:
final ArrayList<YourClazz> results = new ArrayList<YourClazz>();;
for ( YourClazzkey : (Vector<YourClazz>) query.getResultList() )
{
results.add(key);
}
i have faced the same problem. and my entity has no one to one or one to many relationship. then also jpql was giving me queryresult as vector of objects. i changed my solution to query to criteria builder. and that worked for me.
code snippet is as below:
CriteriaBuilder builder = this.entityManager.getCriteriaBuilder();
CriteriaQuery<Timetable> criteria = builder.createQuery(Timetable.class);
Root<Enumeration> root = criteria.from(Timetable.class);
criteria.where(builder.equal(root.get("id"), id));
List<Timetable> topics = this.entityManager.createQuery(criteria) .getResultList();
return topics;
I am in the process of converting an application that uses LINQ to SQL over to LINQ to Entities. I use a repository pattern and I have run in a problem that works in LINQ to SQL but not Entities.
In my data layer, I use LINQ statements to fill my object graph so that none of my database entities are exposed anywhere else. In this example, I have a Lookup Respository that returns a list of Categories. It looks like this:
public IQueryable<Entities.DomainModels.Category> getCategories()
{
return (from c in Categories
where !c.inactive
orderby c.categoryName
select new Entities.DomainModels.Category
{
id = c.categoryID,
category = c.categoryName,
inactive = c.inactive
});
}
Later, I want to put the categories into a sub query and it looks like this:
var d = from p in Programs
let categories = (from pc in p.Categories
join c in getCategories() on pc.categoryID equals c.id
select c)
select new
{
id = p.id,
title = p.title
categories = categories.ToList()
};
When I run this, I get the following error:
LINQ to Entities does not recognize the method 'System.Linq.IQueryable`1[Entities.DomainModels.Category] getCategories()' method, and this method cannot be translated into a store expression.
For reference, the following works though it doesn't return the data I need (it's basically a join):
var q = from p in Programs
from pc in p.Categories
join c in getCategories() on pc.categoryID equals c.id
select new
{
id = p.id,
category = c
};
I understand what the error means in concept however LINQ to SQL would make it work. I have this pattern throughout my data layer and I really want to keep it. Should this be working? If not, how can I modify it without mixing my layers.
You cant pass getCategories() to EF.
The query must be destructible to expression tree.
Calculate getCategories() first.
eg
var simpleList = getCategories().Select(id).Tolist;
then use a contains
where(t=> simpleList.Contains(t.CatId) // or the query syntax equivalent
I have to convert a string value to int, but it seems LINQ to Entities does not support this.
For the following code, I am getting an error.
var query = (from p in dc.CustomerBranch
where p.ID == Convert.ToInt32(id) // here is the error.
select new Location()
{
Name = p.BranchName,
Address = p.Address,
Postcode = p.Postcode,
City = p.City,
Telephone = p.Telephone
}).First();
return query;
LINQ to Entities does not recognize the method 'Int32 ToInt32 (System.String)', and this method can not be translated into a store expression.
Do the conversion outside LINQ:
var idInt = Convert.ToInt32(id);
var query = (from p in dc.CustomerBranch
where p.ID == idInt
select new Location()
{
Name = p.BranchName,
Address = p.Address,
Postcode = p.Postcode,
City = p.City,
Telephone = p.Telephone
}).First();
return query;
No they wouldn't. Think of it this way: both ToString() and Parse() are methods on the objects. Since LINQ to Entities tries to convert your LINQ expression to SQL, those are not available.
If one needs to do this in the query, it might be possible with Cast, which should be available in LINQ to Entities. In the case of ToString, you could use SqlFunctions.StringConvert().
I have an extension method defined like so:
public static TSource MaxBy<TSource, TResult>(this IEnumerable<TSource> collection, Func<TSource, TResult> func) where TSource : class
{
var comparer = Comparer<TSource>.Default;
TSource maxItem = null;
foreach (var item in collection)
{
if (comparer.Compare(item, maxItem) > 0)
maxItem = item;
}
return maxItem;
}
which I then use in the following LINQ-to-Entities query:
var balancesQuery = from t in db.Transactions
where t.UserId == userId
group t by t.CurrencyCode into tg
let tMaxDate = tg.MaxBy(i => i.TsCreate)
join c in db.Currencies on tg.Key equals c.CurrencyCode
select new { Currency = c, Balance = tMaxDate.Balance }
So what I'm doing is - get the newest transaction (MaxBy TsCreate) in each currency (group by CurrencyCode) and then select the balance against each of those transactions.
My problem is - this does not work with Entity Framework (LINQ-to-Entities; I get:
LINQ to Entities does not recognize the method 'Transaction MaxBy[Transaction,DateTime](System.Collections.Generic.IEnumerable'[Transaction], System.Func'2[Transaction,System.DateTime])' method, and this method cannot be translated into a store expression.
The same query works with LINQ to SQL.
My questions are:
Is there a way to make it work with Entity Framework?
Or maybe there is a better way of querying for the same information, which would work with Entity Framework?
Thanks in advance for any help!
Isn't the query same as:
var balancesQuery = from t in db.Transactions
where t.UserId == userId
group t by t.CurrencyCode into tg
join c in db.Currencies on tg.Key equals c.CurrencyCode
select new {
Currency = c,
Balance = tg.OrderByDescending(i => i.TsCreate).Take(1).Balance
};
You can't use extensions with LINQ queries that actually pull data from the database as it's impossible for this to be turned into SQL. However, you can do this by returning the results into memory using ToArray() or ToList() to trigger the database query executing and then call your extension functions on resultant real data in memory.