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C# select duplicate using group

I would like to select only from non-blank Names where any Group contains same ID multiple times:
Data Setup
var a1 = new { id = 3, Name = "", Group = "GroupA" };
var a2 = new { id = 2, Name = "", Group = "GroupA" };
var a3 = new { id = 3, Name = "", Group = "GroupA" };
var b1 = new { id = 4, Name = "B", Group = "GroupB" };
var b2 = new { id = 5, Name = "B", Group = "GroupB" };
var b3 = new { id = 5, Name = "B", Group = "GroupB" };
List<dynamic> group = new List<dynamic>();
group.Add(a1);
group.Add(a2);
group.Add(a3);
group.Add(b1);
group.Add(b2);
group.Add(b3);
Query:
var query1 = group.ToList()
.Where(s=>s.Name != "")
.GroupBy(x =>x.Group)
.Where(g => g.Count() > 1)
.SelectMany(y => y)
.ToList();
Console.WriteLine("output\n" + string.Join("\n", query1));
Returns
id = 4, Name = B, Group = GroupB
id = 5, Name = B, Group = GroupB
id = 5, Name = B, Group = GroupB
But what I wanted is the following:
id = 5, Name = B, Group = GroupB
id = 5, Name = B, Group = GroupB
What am I doing wrong?

Group by id and/or Name depending on your needs
.GroupBy(x => new {x.id, x.Name})
Given
var list = new[]
{
new {id = 3, Name = "", Group = "GroupA"},
new {id = 2, Name = "", Group = "GroupA"},
new {id = 3, Name = "", Group = "GroupA"},
new {id = 4, Name = "B", Group = "GroupB"},
new {id = 5, Name = "B", Group = "GroupB"},
new {id = 5, Name = "B", Group = "GroupB"}
};
Usage
var results = list
.Where(s => s.Name != "")
.GroupBy(x => new {x.id, x.Name})
// .GroupBy(x => x.id) <- depending on your needs
.Where(g => g.Count() > 1)
.SelectMany(y => y);
foreach (var result in results)
Console.WriteLine($"{result.id}, {result.Name}, {result.Group}");
Output
5, B, GroupB
5, B, GroupB

You are applying GroupBy to Group property. Instead of Grouping by Group property, use id property,
Input
var list = new[]
{
new {id = 3, Name = "", Group = "GroupA"},
new {id = 2, Name = "", Group = "GroupA"},
new {id = 3, Name = "", Group = "GroupA"},
new {id = 4, Name = "B", Group = "GroupB"},
new {id = 5, Name = "B", Group = "GroupB"},
new {id = 5, Name = "B", Group = "GroupB"}
};
Solution:
var query1 = list.ToList()
.Where(s=>s.Name != "")
.GroupBy(x =>x.id)
//^^^^^ This change you need to do
.Where(g => g.Count() > 1)
.SelectMany(y => y)
.ToList();
Output
5, B, GroupB
5, B, GroupB
Try it online

Data Set to Tree Structure

I have the below set of data
Where each City belongs to a specific Department, which belongs to a specific Region, which belongs to a specific Country (in this case there is only one country: France).
This data is contained in a CSV file which I can read from on a row-by-row basis, however my goal is to convert this data into a tree structure (with France being at the root).
Each of these nodes will be given a specific Id value, which is something I've already gone and done, but the tricky part is that each node here must also contain a ParentId (for instance Belley and Gex need the ParentId of Ain, but Moulins and Vichy need the ParentId of Aller).
Below is a snippet of code I've written that has assigned an Id value to each name in this data set, along with some other values:
int id = 0;
List<CoverageAreaLevel> coverageAreas = GetCoverageAreaDataFromCsv(path, true);
List<LevelList> levelLists = new List<LevelList>
{
new LevelList { Names = coverageAreas.Select(a => a.Level1).Distinct().ToList(), Level = "1" },
new LevelList { Names = coverageAreas.Select(a => a.Level2).Distinct().ToList(), Level = "2" },
new LevelList { Names = coverageAreas.Select(a => a.Level3).Distinct().ToList(), Level = "3" },
new LevelList { Names = coverageAreas.Select(a => a.Level4).Distinct().ToList(), Level = "4" }
};
List<CoverageArea> newCoverageAreas = new List<CoverageArea>();
foreach (LevelList levelList in levelLists)
{
foreach (string name in levelList.Names)
{
CoverageArea coverageArea = new CoverageArea
{
Id = id++.ToString(),
Description = name,
FullDescription = name,
Level = levelList.Level
};
newCoverageAreas.Add(coverageArea);
}
}
The levelLists variable contains a sort-of heirarchical structure of the data that I'm looking for, but none of the items in that list are linked together by anything.
Any idea of how this could be implemented? I can manually figure out each ParentId, but I'd like to automate this process, especially if this needs to be done in the future.

The solution from #Camilo is really good and pragmatic. I would also suggest the use of a tree.
A sample implementation:
var countries = models.GroupBy(xco => xco.Country)
.Select((xco, index) =>
{
var country = new Tree<String>();
country.Value = xco.Key;
country.Children = xco.GroupBy(xr => xr.Region)
.Select((xr, xrIndex) =>
{
var region = new Tree<String>();
region.Value = xr.Key;
region.Parent = country;
region.Children =
xr.GroupBy(xd => xd.Department)
.Select((xd, index) =>
{
var department = new Tree<String>();
department.Value = xd.Key;
department.Parent = region;
department.Children = xd
.Select(xc => new Tree<String> { Value = xc.City, Parent = department });
return department;
});
return region;
});
return country;
});
public class Tree<T>
{
public IEnumerable<Tree<T>> Children;
public T Value;
public Tree<T> Parent;
}

One way you could solve this is by building dictionaries with the names and IDs of each level.
Assuming you have data like this:
var models = new List<Model>
{
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept1", City = "FranceA" },
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept1", City = "FranceB" },
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept2", City = "FranceC" },
new Model { Country = "France", Region = "FranceRegionB", Department = "FranceDept3", City = "FranceD" },
new Model { Country = "Italy", Region = "ItalyRegionA", Department = "ItalyDept1", City = "ItalyA" },
new Model { Country = "Italy", Region = "ItalyRegionA", Department = "ItalyDept2", City = "ItalyB" },
};
You could do something like this, which can probably be improved further if needed:
var countries = models.GroupBy(x => x.Country)
.Select((x, index) => Tuple.Create(x.Key, new { Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var regions = models.GroupBy(x => x.Region)
.Select((x, index) => Tuple.Create(x.Key, new { ParentId = countries[x.First().Country].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var departments = models.GroupBy(x => x.Department)
.Select((x, index) => Tuple.Create(x.Key, new { ParentId = regions[x.First().Region].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var cities = models
.Select((x, index) => Tuple.Create(x.City, new { ParentId = departments[x.Department].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
The main idea is to leverage the index parameter of the Select method and the speed of dictionaries to find the parent ID.
Sample output from a fiddle:
countries:
[France, { Id = 1 }],
[Italy, { Id = 2 }]
regions:
[FranceRegionA, { ParentId = 1, Id = 1 }],
[FranceRegionB, { ParentId = 1, Id = 2 }],
[ItalyRegionA, { ParentId = 2, Id = 3 }]
departments:
[FranceDept1, { ParentId = 1, Id = 1 }],
[FranceDept2, { ParentId = 1, Id = 2 }],
[FranceDept3, { ParentId = 2, Id = 3 }],
[ItalyDept1, { ParentId = 3, Id = 4 }],
[ItalyDept2, { ParentId = 3, Id = 5 }]
cities:
[FranceA, { ParentId = 1, Id = 1 }],
[FranceB, { ParentId = 1, Id = 2 }],
[FranceC, { ParentId = 2, Id = 3 }],
[FranceD, { ParentId = 3, Id = 4 }],
[ItalyA, { ParentId = 4, Id = 5 }],
[ItalyB, { ParentId = 5, Id = 6 }]

Linq query and potential self join/group by

Suffering sadly from brain fade. I have the following scenario:
void Main()
{
List<CaseBase> caseList = new List<UserQuery.CaseBase>();
caseList.Add(new CaseBase() {CaseID = 1, CaseSequence = 1, CaseStatus = 1});
caseList.Add(new CaseBase() {CaseID = 1, CaseSequence = 2, CaseStatus = 2});
caseList.Add(new CaseBase() {CaseID = 2, CaseSequence = 1, CaseStatus = 1});
var cases = caseList.Where(x => new List<int> {2}.Contains(x.CaseStatus));
}
// Define other methods and classes here
public class CaseBase
{
public int CaseID {get;set;}
public int CaseSequence {get;set;}
public int CaseStatus {get;set;}
}
Which returns the expected
CaseID
CaseSequence
CaseStatus
1
2
2
What I want are all cases with the same ID where one of them has a status of 2.
CaseID
CaseSequence
CaseStatus
1
1
1
1
2
2
Which should be simple but I'm struggling for a simple solution.

There are a couple of ways to proceed:
You can combine the cases by CaseID and select the matching groups and then break them apart:
var cases = caseList
.GroupBy(c => c.CaseID)
.Where(cg => cg.Any(c => new List<int> { 2 }.Contains(c.CaseStatus)))
.SelectMany(cg => cg);
You can find the desired CaseIDs and then get all matching cases:
var wantedCaseIDs = caseList
.Where(c => new List<int> { 2 }.Contains(c.CaseStatus))
.Select(c => c.CaseID)
.ToHashSet();
var cases = caseList.Where(c => wantedCaseIDs.Contains(c.CaseID));

Or you might want to do it like this:
void Main()
{
List<CaseBase> caseList = new List<UserQuery.CaseBase>();
caseList.Add(new CaseBase() { CaseID = 1, CaseSequence = 1, CaseStatus = 1 });
caseList.Add(new CaseBase() { CaseID = 1, CaseSequence = 2, CaseStatus = 2 });
caseList.Add(new CaseBase() { CaseID = 2, CaseSequence = 1, CaseStatus = 1 });
var cases = caseList.Where(x => new List<int> { 2 }.Contains(x.CaseStatus))
.Join(caseList,x => x.CaseID,y => y.CaseID,(x,y) => new {x,y})
.Select(z => z.y)
.Dump();
}

Linq how to find max repeat items?

I have a list of object (ProductInfo).
ProductInfo contains an id, name, and an option.
Imagine this sample, i have this
ProductInfo Id => 1, Name => XXX, Option = A
ProductInfo Id => 1, Name => XXX, Option = B
ProductInfo Id => 2, Name => DEB, Option = A
ProductInfo Id => 2, Name => DEB, Option = B
ProductInfo Id => 2, Name => DEB, Option = C
ProductInfo Id => 3, Name => ZZZ, Option = D
....
....
We see we have 2 time the option A AND B for product 1 and 2.
My goal will be to obtain the max repeat item for each product in the list.
i would like to obtain as result this :
Id = 1, Name = XXX = A, count = 2
Id =2, Name = DEB, count = 2
How i can do that ?
thanks for your time

try to do this code:
var list = new List<ProductInfo> {
new ProductInfo { Id = 1, Name = "XXX", Option = "A"},
new ProductInfo { Id = 1, Name = "XXX", Option = "B" },
new ProductInfo { Id = 2, Name = "DEB", Option = "A" },
new ProductInfo { Id = 2, Name = "DEB", Option = "B"},
new ProductInfo { Id = 2, Name = "DEB", Option = "C" },
new ProductInfo { Id = 3, Name = "ZZZ", Option = "D" }
};
var x = from p in list
group p by new { p.Id, p.Name, p.Option } into g
select new
{
Id = g.Key.Id,
Name = g.Key.Name,
Count = list.Count(m => m.Name == g.Key.Name)
};
var t = x.Distinct();

You can use GroupBy on the Name and Id parameter. Sorry read that wrong at first.

Linq Grouping the result of group by query

I have the following exemple :
Model mod1 = new Model { Header = "A", canDelete = true,pax=1 };
Model mod2 = new Model { Header = "B", canDelete = true,pax=1 };
Model mod3 = new Model { Header = "A", canDelete = true,pax=2 };
Model mod4 = new Model { Header = "B", canDelete = false,pax=2 };
Model mod5 = new Model { Header = "A", canDelete = true,pax=3 };
Model mod6 = new Model { Header = "B", canDelete = false,pax=3 };
Model mod7 = new Model { Header = "A", canDelete = false,pax=4 };
Model mod8 = new Model { Header = "B", canDelete = true,pax=4 };
I added these models to a listMod
I want to group first by pax number, so I used :
var resultQuery = listMod.GroupBy(p=>p.pax);
How can I re-group the result of my resultQuery by Header and canDelete ?
The aim is to have 3 groups :
1st group : mod1 and mod2
2nd group : mod3 , mod4 , mod5 and mod6
3rd group : mod7 and mod8

Well, there may be a better way, but this one should work, assuming you have always two items for each pax number.
The "trick" is to concatenate the first and second canDelete / Header pair of items grouped by pax, and to group on that value.
Than the list inside the groups are flattened (using SelectMany)
listMod.GroupBy(m => m.pax)
.Select(m => new
{
valuePair = string.Format("{0}-{1}/{2}-{3}", m.First().canDelete, m.First().Header, m.Last().canDelete, m.Last().Header),
value = m.Select(x => x)
})
.GroupBy(m => m.valuePair)
.Select(g => g.SelectMany(x => x.value))
//.ToList();
if you wanna avoid this bad concatenation, you can also do
var result = listMod
.GroupBy(m => m.pax)
.Select(m => new
{
a1 = m.First().canDelete,
a2 = m.First().Header,
b1 = m.Last().canDelete,
b2 = m.Last().Header,
value = m.Select(x => x)
})
.GroupBy(m => new {m.a1, m.a2, m.b1, m.b2})
.Select(g => g.SelectMany(x => x.value))
//.ToList();