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LINQ distinct on groups of information

I have multiple items (List)
I need to get distinct features for the items but the issue is that each item has two features. So both features need to match on GroupTypeId and GroupId to become a distinct group.
I need to group items that have the same features (per above distinct groups found). I don't need features here again at the item level since I will have these per above in a separate object.
I need to keep items order intact, the first item will go in group 1, then second might go in group 1 or group 2 and so on.
Also, each item in group, item number needs to be overwritten per the new sequence in that group.
Can i do above tasks purely with LINQ rather than using nested loops?
In the below sample for items
i have 3 distinct feature groups
and 3 item groups. Item 2 and 4 needs to be grouped together and the line no needs to change to 1 and 2. For item 1 and 3, line number should become as 1.
Need to add to List whose count will be 3
Index[0] will have 2 features and 1 item
Index[1] will have 2 features and 2 items
Index[2] will have 2 features and 1 item
public class ItemPicked
{
public int Id { get; set; }
public string Description { get; set; }
public int LineNumber { get; set; }
public int PartId { get; set; }
public List<ItemFeature> Features { get; set; }
}
public class ItemFeature
{
public string OriginalReceived { get; set; }
public Group Feature { get; set; }
}
public class Group
{
public int Id { get; set; }
public string GroupTypeId { get; set; }
public string GroupId { get; set; }
public int SequenceNo { get; set; }
}
public class PickedGrouping
{
public List<ItemFeature> Features { get; set; }
public List<ItemPicked> Items { get; set; }
}
var SampleFeatures1 = new List<ItemFeature>() {
new ItemFeature {
OriginalReceived = "SomeThing",
Feature = new Group() {
Id = 1, SequenceNo = 1, GroupTypeId = "A", GroupId = "B"
}
},
new ItemFeature {
OriginalReceived = "SomeThing2",
Feature = new Group() {
Id = 2, SequenceNo = 2, GroupTypeId = "Y", GroupId = "Z"
}
}
};
var SampleFeatures2 = new List<ItemFeature>() {
new ItemFeature {
OriginalReceived = "SomeThing3",
Feature = new Group() {
Id = 3, SequenceNo = 3, GroupTypeId = "C", GroupId = "D"
}
},
new ItemFeature {
OriginalReceived = "SomeThing4",
Feature = new Group() {
Id = 4, SequenceNo = 4, GroupTypeId = "X", GroupId = "Y"
}
}
};
var SampleFeatures3 = new List<ItemFeature>() {
new ItemFeature {
OriginalReceived = "SomeThing5",
Feature = new Group() {
Id = 3, SequenceNo = 3, GroupTypeId = "C", GroupId = "D"
}
},
new ItemFeature {
OriginalReceived = "SomeThing5",
Feature = new Group() {
Id = 2, SequenceNo = 2, GroupTypeId = "M", GroupId = "K"
}
}
};
var items = new List<ItemPicked>(){
new ItemPicked{
Id = 1, Description = "Item 1", LineNumber = 1, Features = SampleFeatures1
},
new ItemPicked{
Id = 2, Description = "Item 2", LineNumber = 2, Features = SampleFeatures2
},
new ItemPicked{
Id = 3, Description = "Item 3", LineNumber = 3, Features = SampleFeatures3
},
new ItemPicked{
Id = 4, Description = "Item 4", LineNumber = 4, Features = SampleFeatures2
}
};
var pickedGroupings = new List<PickedGrouping>();
PickedGrouping selectedGroup = null;
foreach (var item in items)
{
var found = 0;
if(item.Features == null || !item.Features.Any())
{
selectedGroup = pickedGroupings.FirstOrDefault(x => x.Features == null || !x.Features.Any());
if (selectedGroup == null) selectedGroup = new PickedGrouping();
selectedGroup.Features.AddRange(item.Features);
}
else
{
foreach (var feature in item.Features)
{
foreach (var pg in pickedGroupings)
{
if ((item.Features == null || !item.Features.Any()) && (pg.Features == null || !pg.Features.Any())){
selectedGroup = pg;
found += 1;
}
else
{
foreach (var pgf in pg.Features)
{
if (pgf.Feature == null) continue;
if (pgf.Feature.GroupId == feature.Feature.GroupId && pgf.Feature.GroupTypeId == feature.Feature.GroupTypeId)
{
selectedGroup = pg;
found += 1;
}
}
}
}
}
if (found < 2)
{
pickedGroupings.Add(new PickedGrouping() { Features = item.Features });
selectedGroup = pickedGroupings[pickedGroupings.Count - 1];
}
}
//add item
if (selectedGroup.Items == null) selectedGroup.Items = new List<ItemPicked>();
selectedGroup.Items.Add(item);
}
//update line number
foreach(var pg in pickedGroupings)
{
var lineNum = 1;
foreach(var item in pg.Items)
{
item.LineNumber = lineNum;
lineNum += 1;
}
}

List union that depends / selects on property values

I have a class "item":
public class Item
{
public int Id { get; set; }
public decimal Price { get; set; }
public override bool Equals(object obj)
{
if (obj is Item item)
return item.Id == Id;
return false;
}
// GetHashCode omitted...
}
And I have 2 lists that I need to union:
var items1 = new List<Item>
{
new Item { Id = 1, Price = 10 },
new Item { Id = 2, Price = 10 },
new Item { Id = 3, Price = 10 },
};
var items2 = new List<Item>
{
new Item { Id = 1, Price = 10 },
new Item { Id = 2, Price = 8 },
new Item { Id = 4, Price = 10 },
};
The union I get like this:
var union = items1.Union(items2).ToList();
But I need also the constraint that the items with the lowest price is in the union. So for example in the above lists Item.ID = 2 from "items2" must be in the union...so the result should be a list consisting of these 4 items:
Item { Id = 1, Price = 10 }
Item { Id = 2, Price = 8 } // Not the one with Price = 10
Item { Id = 3, Price = 10 }
Item { Id = 4, Price = 10 }
Is there an elegant way of doing this in C# (preferably using Linq)?

You can try using groupby, like below :
var result = items1.Union(items2).GroupBy(x => x.Id)
.Select(x => new Item
{
Id = x.Key,
Price = x.Min(i => i.Price)
});

How can I join different property object collections

I have a list of my issue class
var firstList = new List<object> {
new { id =1, Name = "item-1"},
new { id =2, Name = "item-2"},
new { id =3, Name = "item-3"},
new { id =4, Name = "item-4"}
}
And my second list is like this
var secondList = new List<Issue> {
new Issue{ id =1, Date = "01.01.2017"},
new Issue{ id =2, Date = "01.02.2017"}
}
So I want to create a new list like this. (same id objects will be isPlanned=true)
var firstList = new List<object> {
new { id =1, Name = "item-1", isPlanned=true, Date = "01.01.2017"},
new { id =2, Name = "item-2", isPlanned=true, Date = "01.02.2017"},
new { id =3, Name = "item-3", isPlanned=false },
new { id =4, Name = "item-4", isPlanned=false }
}
How can I do this linq functions or lambda operations?

You can use left join for this:
var items = new[] {
new { id =1, Name = "item-1"},
new { id =2, Name = "item-2"},
new { id =3, Name = "item-3"},
new { id =4, Name = "item-4"}
};
var issues = new[] {
new { id =1, Date = "01.01.2017"},
new { id =2, Date = "01.02.2017"}
};
var joined = from item in items
join issue in issues on item.id equals issue.id into gj
from sub in gj.DefaultIfEmpty()
select new { item.id, item.Name, isPlanned=sub?.Date != null, sub?.Date };
foreach (var t in joined) {
Console.WriteLine("{0} {1} {2} {3}", t.id, t.Name, t.isPlanned, t.Date);
}
The result will have nulls when dates are missing, i.e.
new { id =1, Name = "item-1", isPlanned=true, Date = "01.01.2017"},
new { id =2, Name = "item-2", isPlanned=true, Date = "01.02.2017"},
new { id =3, Name = "item-3", isPlanned=false, Date = null },
new { id =4, Name = "item-4", isPlanned=false, Date = null }
Demo.

If you wanted to use a lambda expression, you could do it the following way:
List<Foo> foos = new List<Foo>()
{
new Foo(){ Id = 1, Name = "item-1"},
new Foo(){ Id = 2, Name = "item-2"},
new Foo(){ Id = 3, Name = "item-3"},
new Foo(){ Id = 4, Name = "item-4"}
};
List<Bar> bars = new List<Bar>()
{
new Bar(){ Id = 1, Date = "01.01.2017"},
new Bar(){ Id = 2, Date = "01.02.2017"}
};
IEnumerable<dynamic> result = foos.GroupJoin(bars,
f => f.Id,
b => b.Id,
(foo, bar) => new
{
Id = foo.Id,
Name = foo.Name,
isPlanned = String.IsNullOrEmpty(bar.SingleOrDefault()?.Date),
Date = bar.SingleOrDefault()?.Date
});
here are the classes
public class Foo
{
public int Id { get; set; }
public string Name { get; set; }
}
public class Bar
{
public int Id { get; set; }
public string Date { get; set; }
}
I noticed also from the comments from another answer that you are not able to use C#6.0, so this section would not work for you
isPlanned = String.IsNullOrEmpty(bar.SingleOrDefault()?.Date),
Date = bar.SingleOrDefault()?.Date
You can replace that with the following:
isPlanned = bar.SingleOrDefault() == null ? false : String.IsNullOrEmpty(bar.SingleOrDefault().Date),
Date = bar.SingleOrDefault() == null ? null : bar.SingleOrDefault().Date

LINQ group list and combine collections

Given these classes:
public class Employee
{
public int EmployeeId { get; set; }
public int GroupId { get; set; }
public List<Plans> Plans { get; set; }
}
public class Plan
{
public int PlanYearId { get; set; }
public string Name { get; set; }
}
And given a setup like so:
var employees = new List<Employee> {
new Employee {
EmployeeId = 1,
GroupId = 1,
Plans = new List<Plan> {
new Plan {
PlanReferenceId = 1111,
Name = "Benefit 1"
}}};
new Employee {
EmployeeId = 1,
GroupId = 1,
Plans = new List<Plan> {
new Plan {
PlanReferenceId= 2222,
Name = "Benefit 2"
},
new Plan {
PlanReferenceId= 2222,
Name = "Benefit 3"
}}}};
How can I use LINQ to group these employees by both EmployeeId and GroupId and then combine the two List<Plan> properties so that i would end up with something like this:
var employee = new Employee
{
EmployeeId = 1,
GroupId = 1,
Plans = new List<Plan> {
new Plan {
PlanReferenceId = 1111,
Name = "Benefit 1"
},
new Plan {
PlanReferenceId = 2222,
Name = "Benefit 2"
},
new Plan {
PlanReferenceId = 2222,
Name = "Benefit 3"
}
}
}

Just use combination of GroupBy and SelectMany:
var result = employees
.GroupBy(e => new { e.EmployeeId, e.GroupId })
.Select(g => new Employee
{
EmployeeId = g.Key.EmployeeId,
GroupId = g.Key.GroupId,
Plans = g.SelectMany(e => e.Plans).ToList()
}).ToList();

C# LINQ Take limited results per grouped

I have list that includes class named 'ID', 'Name' and 'Category'. There are 6 item in list.
List<MyData> list =
{
{0, "John", "Police"},
{1,"Michael", "Police"},
{2,"Alice", "Police"},
{3, "Ferdinand", "Thief"},
{4, "Jocas", "Thief"},
{5, "Connor", "Thief"}
};
I wanna list them with limited quantity per group by 'Category' with LINQ.
Example : I want list 2 item for each 'Cateogory'. Listed should be below :
John Police
Michael Police
Ferdinand Thief
Jocas Thief

Use combination of Take and SelectMany:
var results = list.GroupBy(x => x.Category).SelectMany(g => g.Take(2)).ToList();
I've tested it on following Item class:
public class Item
{
public int ID { get; set; }
public string Name { get; set; }
public string Category { get; set; }
}
And query:
List<Item> list = new List<Item>
{
new Item { ID = 0, Name = "John", Category = "Police"},
new Item { ID = 1, Name = "Michael", Category = "Police"},
new Item { ID = 2, Name = "Alice", Category = "Police"},
new Item { ID = 3, Name = "Ferdinand", Category = "Thief"},
new Item { ID = 4, Name = "Jocas", Category = "Thief"},
new Item { ID = 5, Name = "Connor", Category = "Thief"}
};
var results = list.GroupBy(x => x.Category).SelectMany(g => g.Take(2)).ToList();
Returns 4 elements, right as you want.