I have an IEnumerable containing values like "ABC", "DEF", etc.
I'm trying to form a LINQ query where the value of a property in my object may be equal to one of the many values contained in my IEnumerable. How do I form that LINQ query?
var statesFilter = new List<string>();
statesFilter.Add("NY");
statesFilter.Add("CA");
var employees = new List<Employee>();
employees = getDataFromSomewhere();
// Code below is not working. Just wanted to give you an idea about my LINQ query
var myFilteredList = employees.Where(x => x.State.Contains(statesFilter));
Employee class could be something like this:
public class Employee
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string State { get; set; }
}
If State property is of type string, you should change your Where to the following:
var myFilteredList = employees.Where(x => statesFilter.Contains(x.State));
Also, you can do this:
var myFilteredList = employees.Where(x => statesFilter.Any(s=>s==x.State));
Condition should be
x=>statesFilter.Contains(x.State))
Related
Please have patience with me I'm new to linq and have a question about a couple of errors that I am not understanding any help would be greatly appreciated.
the error I am receiving in the title of my question.
my childproduct variable returns every single character indiviuallly I would like them to be a string version of the productId and Childtext parameters.
Code:
public class AOAPlusChildModel
{
public List<string> LongName { get; set; }
public List<string> Text { get; set; }
public List<string> ProductId { get; set; }
public static List<AOAPlusChildModel> GetChildProducts()
{
List<AOAPlusChildModel> cp = new List<AOAPlusChildModel>();
List<AoaUserDefinedVWGetAOAPlusProducts> ChildProductsLists = AoaSvcClient.Client.Context.AoaUserDefinedVWGetAOAPlusProductss.Where(a => a.MasterProductFlag == false && a.Affiliate == "VA").ToList();
var childProducts = ChildProductsLists.SelectMany(p => p.LongName, (id, childtext) =>
new { ProductId = id.ProductId, Text = childtext }).ToList();
cp = childProducts.ToList();
return cp;
}
}
Your variable cp is a List<AOAPlusChildModel> but the linq query is projecting an anonymous type. Instead of creating a new anonymous type create a new AOAPlusChildModel
return ChildProductsLists.SelectMany(p => p.LongName,
(id, childtext) =>
new AOAPlusChildModel {
ProductId = id.ProductId,
Text = childtext }).ToList();
Reason for following errors are that you perform ChildProductsLists.SelectMany(p => p.LongName) which basically now returns a collection of strings - this collection of strings you are trying to assign as a new AOAPlusChildModel object which does not hold string properties but List<string> properties.
I think your model should look like:
public string LongName { get; set; }
public string Text { get; set; }
public string ProductId { get; set; }
I have Medals class, I call a service that return all Medal class fields except for the two fields ArabicName and ISOCode; Which I have to bring them from another table class "CountrysTBLs" , I made this join code:
The Medal class:
public class Medals {
public int bronze_count { get; set; }
public string country_name { get; set; }
public int gold_count { get; set; }
public string id { get; set; }
public int place { get; set; }
public int silver_count { get; set; }
public int total_count { get; set; }
public string ArabicName { get; set; } // this field not return by service
public string ISOCode { get; set; } // this field not return by service
}
The code:
var cntrs = db.CountrysTBLs.ToList();
List<Medals> objs = call_Service_Of_Medals_Without_ISOCode();
IEnumerable<Medals> query = from obj in objs
join cntry in cntrs on obj.country_name equals '%' + cntry.CommonName + '%'
select new Medals
{
ArabicName = cntry.ArabicName,
ISOCode = cntry.ISOCode,
country_name = obj.country_name,
place = obj.place,
gold_count = obj.gold_count,
silver_count = obj.silver_count,
bronze_count = obj.bronze_count,
total_count = obj.total_count
};
I get no result?!
How to fix that? Is there is any way to bring the two fields (ISOCode, ArabicName) without even use the inner join, and in same time best performance?
You want something like this to achieve LIKE functionality
List<Medals> medals = new List<Medals>();
var list = medals.Select(x => new
{
obj = x,
country = countries.FirstOrDefault(c => c.CommonName.Contains(x.country_name))
});
or something like this (if you want to just enrich each medal)
foreach (var medal in medals)
{
var country = countries.FirstOrDefault(c => c.CommonName.Contains(x.country_name));
medal.ISOCode = country.ISOCode;
medal.ArabicName = country.ArabicName;
}
Do note that this is not as performant as a Dictionary<string,Coutnry> of countries where the key is the country name, but as you need a LIKE comparison you would need to bring in a custom data structure such as Lucene index for fast lookups. But check first, if the lists are small enough, it probably won't be a problem. Otherwise, why not make the Medal.Country_Name and Country.Name the same? So you can do quick Dictionary (hashtable) lookups
Is it possible to select a single object and populate a containing IEnumerable property with a single Lambda expression?
Something like this:
var someViewModel = _repository.Table.Where(x => x.Id == someId)
.Select(new ListViewModel(){
GroupId = x.Group.Id,
GroupTitle = x.Group.Title
List = ?? // Select new SubViewModel and add it to IEnumerable<SubViewModel>
})
The result I'm after is a new object (ListViewModel in this case) that contains 3 properties. "List" being a collection of newly selected objects.
Is this possible? Am I coming at this from the wrong angle?
Thanks!
Update:
Let me try again :) Keep in mind that my naming is fictional here. Given the following two classes I would like to construct a DB query using a Lambda expression which creates a single "ListViewModel" that contains a collection of "SubViewModel". Does this help clarify?
public class SubViewModel
{
public int Id { get; set; }
public string Title { get; set; }
}
public class ListViewModel
{
public int GroupId { get; set; }
public string GroupTitle { get; set; }
public IEnumerable<SubViewModel> List { get; set; }
}
I'm not sure if I understand your question correctly but here is what I am thinking, you need to create a new IEnumberable and add the item to that collection.
var someViewModel = _repository.Table.Where(x => x.Id == someId)
.Select(new ListViewModel()
{
GroupId = x.Group.Id,
GroupTitle = x.Group.Title
List = new List<SubViewModel> { new SubViewModel(x) }
});
I have an object lets say its classrooms that is returned from the repository but I use an anonymous type for my View so I convert it like so
return from P in db.ClassRooms
where P.LocationId == LocationId && P.IsApproved==true
select new ClassRoomsViewModel
{
Id = P.Id,
Created = P.CreatedOn,
IsApproved = P.IsApproved,
IsDeleted = P.IsDeleted,
Desks = ??
}
the problem is I am not sure how to handle the desk object.
In my ClassRoomsViewModel class Desks is a list object
public class ClassRoomsViewModel{
public long Id { get; set; }
public DateTime Created { get; set; }
public List<DeskViewModel> Desks { get; set; }
}
public class DeskViewModel{
public long Id { get; set; }
public string Name{ get; set; }
}
The classrooms dataobject is link as a reference to the Desk Object.
so from the above linq query P.Desks.Name will return the name of all objects in the classroom for the linq query
You need to take the collection of desks from the data model, convert each one to a DeskViewModel, and convert the resulting sequence to a List<T>.
That would look something like
p.Desks.Select(d => new DeskViewModel { ... }).ToList()
If P.Desks.Name and P.Desks.Id are arrays you could do it like this with zip.
return from P in db.ClassRooms
where P.LocationId == LocationId && P.IsApproved==true
select new ClassRoomsViewModel
{
Id = P.Id,
Created = P.CreatedOn,
IsApproved = P.IsApproved,
IsDeleted = P.IsDeleted,
Desks = P.Desks.Name.Zip(P.Desks.Id,
(n, i) => new DeskViewModel { Id = i, Name = n });
}
I have a IQueryable<SomePOCO> (a LINQ-Entities query, if that matters):
public class SomePOCO
{
public string ParentName { get; set; }
public string Name { get; set; }
public string Url { get; set; }
}
And i'm trying to project to a single object (anonymous type would be best, since i only need method scope) which has 2 properties:
public string ParentName { get; set; }
public ICollection<SimplePoco> { get; set;
SimplePOCO is as follows:
public class SimplePOCO
{
public string Name { get; set; }
public string Url { get; set; }
}
The reason i'm doing this is that all of the "SomePOCO"s im retrieving have the same ParentName, so i just want that once, as opposed to bringing over the wire the same value N amount of times and doing a .First().
Hope that makes sense.
The end result is i should be able to do this:
var parentName = result.ParentName; // string
var pocos = result.SimplePOCOs; // ICollection<SimplePOCO>
I think i either need some kind of aggregation, like with GroupBy or SelectMany.
Any ideas?
I think you just need to do a group by Parent Name
var result = collection.GroupBy(i => i.ParentName)
.Select(g => new {
ParentName = g.Key,
SimplePocos = g.Select(i => new SimplePoco
{
Name = i.Name,
Url = i.Url
})
});
This is the first step.
var groups = myQ.GroupBy(p => p.ParentName);
You will need to have your middle data structure. I'll call it Grouping.
var myList = new List<Grouping>();
foreach (var group in groups) {
var newGrouping = new Grouping();
new Grouping.ParentName = group.Key;
newGrouping.SimplePocos = group.Select(p => new SimplePoco(p)).ToArray();
}
You should have a constructor of SimplePoco that will convert it for you.