I have two classes Teams and PlayerTeams
public class PlayerTeams
{
public int ID { get; set; }
public string PlayerName { get; set; }
public string PlayerCountry { get; set; }
public bool IsActive { get; set; }
public string PlayerTeam { get; set; }
}
public class Players
{
public int ID { get; set; }
public string Name { get; set; }
public string Country { get; set; }
public bool? Status { get; set; }
}
I have a list of PlayerTeams which is grouped by PlayerTeam like this.
var groupedPlayers = teams
.OrderBy(x => x.PlayerName)
.GroupBy( x => x.PlayerTeam)
.ToList();
Its of type List<IGrouping<string, PlayerTeams>> but I want it to be of type List<IGrouping<string, Players>> as I do not want the redundant key information on every row.
How could I possibly achieve that? I could only think of something like .ConvertAll() on the IGrouping. I am not able to make it also.
Is there an efiicient way to do this?
If you can change the grouping, I'd just use:
var groupedPlayers = teams
.OrderBy(x => x.PlayerName)
.GroupBy(x => x.PlayerTeam, Players.FromPlayerTeam)
.ToList();
Where Players.FromPlayerTeam is a static method in Players which takes a PlayerTeam and returns a Players.
Additionally, I'd suggest using ToLookup instead of GroupBy - a Lookup is exactly what you want here, without bothering with the ToList call.
This not testet, just an idea.
If you have trouble converting your linq statement, which is expecting the IGrouping type, to a string list, then you might have to select it before.
var groupedPlayers = new List<string>();
groupedPlayers = teams
.OrderBy(x => x.PlayerName)
.GroupBy(x => x.PlayerTeam, Players.FromPlayerTeam)
.Select(x => x.Key) // << added select
.ToList();
Related
I have a model Group:
public class GroupModel
{
[Key]
public int GroupModelId { get; set; }
[Required]
[MaxLength(50)]
[DataType(DataType.Text)]
public string GroupName { get; set; }
[Required]
public virtual ICollection<FocusArea> FocusAreas { get; set; }
...
And a model Focus:
public class FocusArea
{
public int FocusAreaId { get; set; }
public FocusEnum Focus { get; set; }
public List<ApplicationUser> ApplicationUser { get; set; }
public virtual ICollection<GroupModel> GroupModel { get; set; }
public enum FocusEnum
{
Psych,
Medical,
LivingWith
}
Group and Focus has a many-to-many relationship. My Controller is receiving:
public ActionResult GroupSearch(string[] focusSelected) // Values possible are Pysch, Medical and LivingWith
{
List<GroupModel> groups;
...
Problem: I want to select the groups that have all the focus that are inside the focusSelected array.
What I've tried:
groups = groups.Where(t => t.FocusAreas.Where(x => focusSelected.Contains(x.Focus))).ToList()).ToList();
Obviously not working. Does anyone have another idea?
This may help you
var result = groups.Where(g => g.FocusAreas.All(f => focusSelected
.Any(fs => (FocusEnum)Enum.Parse(typeof(FocusEnum), fs, true) == f.Focus)));
Where needs a delegate / expression that returns bool. In your sample - you are putting Where inside Where, where Where returns collection.
Changing inner Where to All should do the trick:
var allSelParsed = focusSelected.Select(s => (FocusEnum)Enum.Parse(typeof(FocusEnum), s)
.ToList();
groups = groups.Where(gr => allSelParsed.All(selected =>
gr.FocusAreas.Any(fc =>
fc.Focus == selected)))
.ToList();
This should give you expected result
var result = groups.Where(g =>
focusSelected.All(fs =>
g.FocusAreas.Any(fa => fa.ToString() == fs)));
I am aggregating data that I retrieve from multiple identical web services. The same row count and data points are returned with only a variance in the Value. The GroupBy clause I am using is not condensing any of the rows. I have the same row count before and after the GroupBy.
MyWebServiceUrls
.AsParallel()
.SelectMany(url => GetMetricItemData(url))
.GroupBy(item => new { item.DateTime, item.Group, item.Metric }, item => item.Value)
.Select(grp => new MetricItem()
{
DateTime = grp.Key.DateTime,
Group = grp.Key.Group,
Metric = grp.Key.Metric,
Value = // type = decimal?
grp.Any(mi => mi.HasValue)
? grp.Key.Metric.AggregationType == Metric.MetricAggregationTypes.Sum
? grp.Sum(mi => mi.Value)
: grp.Average(mi => mi)
: null
})
.AsEnumerable();
The syntax looks correct based on other examples I have found.
I send this data back to my database and can aggregate with the statement GROUP BY [DateTime], [Group], [Metric] and everything works great. While I can use the database to solve this issue, I would like to know how to correctly use LINQ in this instance.
What am I missing to get this LINQ expression to work?
UPDATE:
This is the relevant MetricItem and Metric class definition:
public class MetricItem
{
public string Group { get; set; }
public DateTime DateTime { get; set; }
public Metric Metric { get; set; }
public Decimal? Value { get; set; }
}
public class Metric
{
public string Code { get; set; }
public string Label { get; set; }
private List<string> SumMetrics = new List<string>(new string[] { "TPI", "TPO", "TPIO" });
public enum MetricAggregationTypes { Sum, Average };
public MetricAggregationTypes AggregationType
{
get
{
if (SumMetrics.IndexOf(this.Code) >= 0)
return MetricAggregationTypes.Sum;
else
return MetricAggregationTypes.Average;
}
}
}
You need to override Equals and GetHashCode on the Metric class. Most Linq methods use hash codes for comparison operations, so for most objects you define yourself, you need to override this class if you plan to use something like GroupBy, Union, etc.
I have a Comment and Votes related to the comment.
[Table("QAComment")]
public class QaComment : IEntity
{
[Key, Column("QACommentID")]
public int Id { get; set; }
// ...
public virtual ICollection<QaCommentVote> Votes { get; set; }
[NotMapped]
public int OverallVote { get; set; }
}
[Table("QACommentVote")]
public class QaCommentVote : IEntity
{
[Key, Column("QACommentVoteID")]
public int Id { get; set; }
[ForeignKey("QAComment")]
public int QaCommentId { get; set; }
public int Value { get; set; }
public virtual QaComment QaComment { get; set; }
}
I need to get comments with the sum of their votes, not pulling all votes to the application.
The ways I can see to achive this:
1. Make a database view for Commment and calc votes sum in there.
Cons: dont wanna make extra-views
2. Via LINQ:
var comments =
Set<QaComment>()
.Select(c => new QaComment() {/* assign every property once again and calc OverallVote */});
Cons: don't like to assign allproperties once again.
Is there a better way devoid of that cons?
UPDATE
This is what I want as a result of LINQ:
SELECT
qac.*,
(SELECT SUM(v.Value)
FROM QACommentVote v
WHERE v.QACommentID = qac.QACommentID) as OverallVote
FROM QAComment qac
You can fetch QaComment and the sum you're looking for separately as anonymous type and merge them into one object using LINQ to Objects:
var comments
= Set<QaComment>()
.Select(c => new { c, sum = c.Votes.Sum(v => v.Value))
.AsEnumerable() // to make next query execute as LINQ to Objects query
.Select(x => { x.c.OverallVote = x.sum; return x.c; })
.ToList();
But to make point clear: I haven't tested that :)
public class Employee
{
public int Id { get; set; }
public string Title { get; set;}
//....other fields....
//......
//public Topics Interest { get; set; }
public IList<Topics> Interests { get; set; }
}
public class Topics
{
public int Id { get; set; } ;
public string Name { get; set; } ;
//other fields
}
public static IQueryable<EmployeeObject> QueryableSQL()
{
IQueryable<EmployeeObject> queryable = EmployeeRepository.GetAllEmployee();
}
My above data structure has Employee and within it has multiple interests and each interest has multiple topics
My Question is:
How would i search Employee.Interests.Name ?
//i need help construct the linq....
//the below will not work and look for something in the `EmployeeObject` rather in `Interests`
IList<EmployeeObject> _emps = QueryableSQL().Where(x => x.Name== "Chess").ToList();
It depends on what you want. Do you want items where any of their interests match a given value?
var query = QueryableSQL().Where(employee =>
employee.Interests.Any(interest => interest.Name == "Chess"));
When you've been able to explain in English the query that you want the translation to LINQ will be a lot easier.
You can use Any on the child collection to find matching EmployeeObjects
IList<EmployeeObject> _emps =
QueryableSQL().Where(x => x.Interests
.Any(i => i.Name== "Chess"))
.ToList();
i have
public class Menu
{
public int ID { get; set;}
public List<Task> Tasks { get; set; }
}
public class Task
{
public int ID { get; set; }
public byte[] Image { get; set; }
public string Name { get; set; }
}
i would like to know all tasks which has a certain List ID using LINQ queries
Try
var result = Menus.Where(menu => menu.ID == id)
.Select(menu => menu.Tasks)
.FirstOrDefault();
Also you may want to peruse http://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b as this would answer most of your queries like the above.
You can use Enumerable.Where
var list = Tasks.Where(l=>l.ID ==x);
or
var list = from t in Tasks
where t.ID == x
select t;
x will be the id you need to compare