I have two ILIst of these objects:
class ProductionMachineType
{
string code { get; set; }
IEnumerable<string> ProductionToolsLink { get; set; }
}
class ProductionTools
{
string code { get; set; }
}
I am looking for a fast Linq method that make me able to query the IList<ProductionMachineType> that contains at least one ProductionToolsLink contained inside the ILIst<ProductionTools>.
In SQL I would wite something like this:
SELECT
*
FROM
IList<ProductionMachineType>
WHERE
IList<ProductionMachineType>.ProductionToolsLink IN ILIst<ProductionTools>
Is there a way to do this?
Contains method can help you:
var names = new string[] { "Alex", "Colin", "Danny", "Diego" };
var matches = from person in people
where names.Contains(person.Firstname)
select person;
This will do it, but I can't guarantee how efficient it is...
var output = machines.Where(machine =>
machine.ProductionToolsLink
.Any(link => tools.Select(tool => tool.code).Contains(link)));
Related
I have a list of Cutdetails. I am trying to write a function using LINQ that will return the count of bars in the list where the CODE , BRAND, CODE and LENGTH all match. I want to be able to specify all these parameters and return a number for the number of matches.
I have tried using foreach statements which is fine but i'm sure there is an neater and smarter way to do it using LINQ. Any suggestions?
List<Bar> bars = new List<Bar>();
public class Bar
{
public string Brand { set; get; }
public string System { set; get; }
public string Code { set; get; }
public string Length { set; get; }
}
Thanks in advance!
Will
You can filter using the match and then do a count.
var occurences = bars.Where(x => x.Brand == "Brand" && x.Code == "code").Count();
I have a class Product:
class Product
{
int Id { get; set; }
string Name { get; set; }
int CategoryId { get; set; }
int PlantId { get; set; }
DateTime ProductionDate { get; set; }
}
I would like to use the LINQ GroupBy on multiple properties but I do not know in advance how many and which properties. For instance I might want to group by just CategoryId, just PlantId or both. I found an article on the net that describes how to use LINQ GrouBy dinamically.
This might work good indeed but if I want to perform the Group By on ProductionDate.Year and ProductionDate.Month without knowing the granularity in advance? As granularity I mean whether I want to group all the Products produced in a specific year or narrow the group by to the month.
The only logical solution that I found is:
public ProductInfo GetGroupedProducts(int? year, int? month, int? selectedCategoryId, int? selectedPlantId)
{
List<Product> products = GetProducts();
var groupedProducts = products.GroupBy(p => new { (year == null ? p.ProductionDate.Year : string.Empty),
(month == null ? p.ProductionDate.Month : string.Empty),
(selectedCategoryId == null ? p.CategoryId : string.Empty),
(selectedPlantId == null ? p.PlantId : string.Empty)
});
//perform some additional filtering and assignments
}
But I guess there could be a cleaner and more proper solution. With the old style way of building queries, based on strings, this task was much easier to accomplish. If there is no other way, I really think this is a part of LINQ that needs to be improved.
The cleaner solution is to use this extension method:
public static TResult With<TInput, TResult>(this TInput? o, Func<TInput, TResult>
selector, TResult defaultResult = default(TResult)) where TInput : struct
{
return o.HasValue ? selector(o.Value) : defaultResult;
}
Like this:
string result = year.With(T => p.ProductionDate.Year, string.Empty);
of this, if nulls are okay:
string result = year.With(T => p.ProductionDate.Year);
or something with T which is int in case the int? has value.
But, you know, the better solution is out there, so feel free to expand your code so I could analyze it.
If I understand what you are asking, I had a similar issue Reversing typeof to use Linq Field<T>
I would do something like
public static IEnumerable<IGrouping<string, TElement>> GroupMany<TElement>(
this IEnumerable<TElement> elements,
params Func<TElement, object>[] groupSelectors)
{
return elements.GroupBy(e => string.Join(":", groupSelectors.Select(s => s(e))));
}
then you can call your function like
var groupedProducts = products.GroupMany(p => p.CategoryId , p => p.ProductionDate.Month);
The function groups via a string of the properties divided by a colon. The reason why I did this is because the hashcode for strings are guaranteed to be the same as opposed to a class.
I have this structure:
class Foo {
IList<FooAttribute> Attributes { get; set; }
}
class FooAttribute {
bool IsSelected { get; set; }
string Value { get; set; }
}
And I have objects like:
IQuerable<Foo> foos; // Database repository object .AsQuerable()
IList<FooAttribute> attrs;
I need to filter only those items of foos that have all attributes of attrs list.
I tried this:
foos = foos.Where(foo =>
attrs.All(a =>
foo.Attributes.Any(at => at.Value == a)));
var filteredFoos = foos.ToList();
and i think it would work, but would be super slow and... it throws NotSupportedException...
By the way... I use ASP.NET MVC 3 and C# 4.0, so even the newest solutions are very welcome.
Thanks in advance.
FooAttribute fooAttributeAlias=null;
Session.QueryOver<Foo>().Inner.JoinAlias(x=>x.Attributes,()=>fooAttributeAlias)
.WhereRestrictionOn(()=>fooAttributeAlias).IsNotEmpty
.List();
I did not understand the query that you have written. I am not sure if the above query does what you expect, see the generated sql and see if it is correct.
Also what might help is the sql query that you expect to see which will give you the correct result.
I've got some data in a table that looks like so:
Recipe | Category | Email
What I'd like to do is pull this data back from the source and put it into something that looks like so:
public class RecipeItem
{
public long Recipe { get; set; }
public long Category { get; set; }
public List<string> Names {get; set; }
}
Grouping by the Recipe and Category ids and putting all the emails that into the list.
So, what I've tried is to do something like this:
var recipeItems =
from entry in list
group entry by new { entry.Recipe, entry.Category}
into aRecipe
select new RecipeItem()
{
Recipe = aRecipe.Key.Recipe,
Category = aRecipe.Key.Category,
// ? Not sure how to stick the list of names in here
};
list is the data pulled back via entity framework.
But this isn't quite right - I think I'm close here (maybe). What am I missing here on this?
Follow-up:
Thanks to Aducci for clearing this up. The answer is that you can do this:
Names = aRecipe.Select(x => x.Name)
and this will add all those Names which are in each group into the Names collection for that group. Pretty nifty.
I would modify your class to look like this
public class RecipeItem
{
public long Recipe { get; set; }
public long Category { get; set; }
public IEnumerable<string> Names {get; set; }
}
And your link to entities query to:
var recipeItems =
from entry in list
group entry by new { entry.Recipe, entry.Category}
into aRecipe
select new RecipeItem()
{
Recipe = aRecipe.Key.Recipe,
Category = aRecipe.Key.Category,
Names = aRecipe.Select(x => x.Name)
};
Given the follow data class,
public class EmployeeMenu
{
public int ID { get; set; }
public string HeaderName { get; set; }
public List<string> ItemNames { get; set; }
}
how can I get a sub-query into the ItemNames field?
My current query of
IQueryable<EmployeeMenu> retValue =
from mh in menuHeaders
select new EmployeeMenu
{
ID = mh.ID,
HeaderName = mh.HeaderName,
ItemNames = (from mhi in mh.MenuItems
select mhi.MenuItemName).ToList<string>()
};
doesn't seem to be doing the trick...
The data structure is
MenuHeaders MenuItems
----------- ---------
ID ID
HeaderName <-(FK)--MenuHeaderID
MenuItemName
I ended up just changing from a List to IEnumerable. This fixed it.
Wouldnt you want to just put a where in your sub-select to filter that down to all the menu items with the MenuHeaderID equals mh.HeaderName. You can just .Equals() with the StringComparison type if you want as well.
Here is an example...
IQueryable<EmployeeMenu> retValue =
from mh in menuHeaders
select new EmployeeMenu
{
ID = mh.ID,
HeaderName = mh.HeaderName,
ItemNames = (from mhi in mh.MenuItems
select mhi.MenuItemName where mhi.MenuHeaderID = mh.HeaderName).ToList<string>()
};
My guess is that your not initiliazing the list within your class. I basing this off the experience I was having with Nhibernate.
public class EmployeeMenu
{
public int ID { get; set; }
public string HeaderName { get; set; }
public List<string> ItemNames { get; set; }
public EmployeeMenu()
{
ItemNames=new List<string>();
}
}
Hope this helps.
Okay. Try replacing
(from mhi in mh.MenuItems
select mhi.MenuItemName).ToList<string>()
by
mh.MenuItems
.AsEnumerable()
.Select(mhi => mhi.MenuItemName)
.ToList()
I question if you want a where clause in there somewhere, but this should get you past the runtime exception.
Any time you see an error message of the form "LINQ to Entities does recognize the method ... and this method can not be translated into a store expression" LINQ to Entities is telling you that it can't figure out how to translate part of the expression tree into a SQL statement. This means you need to pull things client side so that LINQ to Entities doesn't try to translate something that it can't translate.