I have a collection of objects that each defined by a particular "group". How can I write a LINQ query to produce a count of each object grouped by "group".
As an example, lets say I have the following classes;
public class Release
{
int ReleaseNumber;
public ReleaseDetails[] details;
}
public class ReleaseDetails
{
string Group;
// other details omitted
}
For a given release, I'd like to be able to produce output like;
Release number 1 contains the following details;
- 17 records in Group A
- 12 records in Group B
- 6 records in Group C
Any help is much appreciated.
You can do something like
var q = from d in r.Details
group d by d.Group into counts
select new { Count = counts.Count(), Group = counts.Key };
Full example:
Release r = new Release
{
ReleaseNumber = 1
,
Details = new ReleaseDetails[]
{
new ReleaseDetails { Group = "a"},
new ReleaseDetails { Group = "a"},
new ReleaseDetails { Group = "b"},
new ReleaseDetails { Group = "c"},
new ReleaseDetails { Group = "d"},
new ReleaseDetails { Group = "d"},
new ReleaseDetails { Group = "e"},
}
};
var q = from d in r.Details
group d by d.Group into counts
select new { Count = counts.Count(), Group = counts.Key };
foreach (var count in q)
{
Console.WriteLine("Group {0}: {1}", count.Group, count.Count);
}
Here you go.
public class ReleaseDetails
{
public string Group { get; set; }
public ReleaseDetails() {}
public ReleaseDetails(string grp){Group = grp;}
}
var qry = new Release();
qry.details = new List<ReleaseDetails>();
qry.details.Add(new ReleaseDetails("A"));
qry.details.Add(new ReleaseDetails("A"));
qry.details.Add(new ReleaseDetails("B"));
qry.details.Add(new ReleaseDetails("C"));
qry.details.Add(new ReleaseDetails("C"));
qry.details.Add(new ReleaseDetails("B"));
var result = from x in qry.details
group x by x.Group into g
select new
{
Count = g.Count(),
Group = g.Key
};
//Or using Labmda
var result1 = qry.details.GroupBy(x => x.Group).Select(g => new { Count = g.Count(), Group = g.Key });
Related
I'm a beginner in linq.
I would like to write this query in linq.
Select SUM(importo), anno From(
Select anno, Importo from[Archivio].[dbo].[AAA]
union
Select anno, importo From[Archivio].[dbo].[BBB]) as prova
group by Anno order by anno.
I wrote this:
DataTable Tab_AAA = DS_AAA.Tables[0];
DataTable Tab_BBB = DS_BBB.Tables[0];
IEnumerable<DataRow> query =
(from A in DS_AAA.AsEnumerable()
select A).Union(from B in DS_BBB.AsEnumerable()
select B)
now I can not enter the sum and the group by.
Thank you all
the objects that you are using must be something like this
public class AnnoImporto
{
private int _anno;
private double _importo;
private string _altro;
public AnnoImporto(int aAnno, double aImp, string aAltro)
{
_anno = aAnno;
_importo = aImp;
_altro = aAltro;
}
public int Anno
{
get { return _anno; }
set { _anno = value; }
}
public double Importo
{
get { return _importo; }
set { _importo = value; }
}
public string Altro
{
get { return _altro; }
set { _altro = value; }
}
}
surely you have the year and the amount, think to "altro" as generic eventual other fields. I built two lists of AnnoImporto objects, but the following code will work even on lists of different object (of course, as I just said, just having year and amount...)
List<AnnoImporto> aaa = new List<AnnoImporto>();
List<AnnoImporto> bbb = new List<AnnoImporto>();
aaa.Add(new AnnoImporto(2015, 10,"blabla"));
aaa.Add(new AnnoImporto(2014, 20, "blabla"));
aaa.Add(new AnnoImporto(2013, 15, "blabla"));
aaa.Add(new AnnoImporto(2012, 5, "blabla"));
aaa.Add(new AnnoImporto(2011, 40, "blabla"));
bbb.Add(new AnnoImporto(2011, 50, "blabla"));
bbb.Add(new AnnoImporto(2013, 20, "blabla"));
bbb.Add(new AnnoImporto(2015, 15, "blabla"));
var aaa_mod = from a in aaa
select new
{
Anno = a.Anno,
Importo = a.Importo
};
var bbb_mod = from b in bbb
select new
{
Anno = b.Anno,
Importo = b.Importo
};
var unione = aaa_mod.Union(bbb_mod);
Console.WriteLine("controlliamo la nuova lista:");
foreach (var p in unione)
{
Console.WriteLine($"{p.Anno}, {p.Importo}");
}
var somme = from p in unione
orderby p.Anno
group p.Importo by p.Anno into q
select new
{
Anno = q.Key,
ImportoTotale = q.Sum()
};
Console.WriteLine("controlliamo le somme:");
foreach (var p in somme)
{
Console.WriteLine($"{p.Anno}, {p.ImportoTotale}");
}
I followed step by step your query: first I selected in aaa and in bbb only the fields you need, I made the union of the results and I checked it. Then I did the group by to calculate sums by year.
I am using Dynamic Linq helper for grouping data. My code is as follows :
Employee[] empList = new Employee[6];
empList[0] = new Employee() { Name = "CA", State = "A", Department = "xyz" };
empList[1] = new Employee() { Name = "ZP", State = "B", Department = "xyz" };
empList[2] = new Employee() { Name = "AC", State = "B", Department = "xyz" };
empList[3] = new Employee() { Name = "AA", State = "A", Department = "xyz" };
empList[4] = new Employee() { Name = "A2", State = "A", Department = "pqr" };
empList[5] = new Employee() { Name = "BA", State = "B", Department = "pqr" };
var empqueryable = empList.AsQueryable();
var dynamiclinqquery = DynamicQueryable.GroupBy(empqueryable, "new (State, Department)", "it");
How can I get back the Key and corresponding list of grouped items i.e IEnumerable of {Key, List} from dynamiclinqquery ?
I solved the problem by defining a selector that projects the Key as well as Employees List.
var eq = empqueryable.GroupBy("new (State, Department)", "it").Select("new(it.Key as Key, it as Employees)");
var keyEmplist = (from dynamic dat in eq select dat).ToList();
foreach (var group in keyEmplist)
{
var key = group.Key;
var elist = group.Employees;
foreach (var emp in elist)
{
}
}
The GroupBy method should still return something that implements IEnumerable<IGrouping<TKey, TElement>>.
While you might not be able to actually cast it (I'm assuming it's dynamic), you can certainly still make calls on it, like so:
foreach (var group in dynamiclinqquery)
{
// Print out the key.
Console.WriteLine("Key: {0}", group.Key);
// Write the items.
foreach (var item in group)
{
Console.WriteLine("Item: {0}", item);
}
}
I have a collection of items that contain an Enum (TypeCode) and a User object, and I need to flatten it out to show in a grid. It's hard to explain, so let me show a quick example.
Collection has items like so:
TypeCode | User
---------------
1 | Don Smith
1 | Mike Jones
1 | James Ray
2 | Tom Rizzo
2 | Alex Homes
3 | Andy Bates
I need the output to be:
1 | 2 | 3
Don Smith | Tom Rizzo | Andy Bates
Mike Jones | Alex Homes |
James Ray | |
I've tried doing this using foreach, but I can't do it that way because I'd be inserting new items to the collection in the foreach, causing an error.
Can this be done in Linq in a cleaner fashion?
I'm not saying it is a great way to pivot - but it is a pivot...
// sample data
var data = new[] {
new { Foo = 1, Bar = "Don Smith"},
new { Foo = 1, Bar = "Mike Jones"},
new { Foo = 1, Bar = "James Ray"},
new { Foo = 2, Bar = "Tom Rizzo"},
new { Foo = 2, Bar = "Alex Homes"},
new { Foo = 3, Bar = "Andy Bates"},
};
// group into columns, and select the rows per column
var grps = from d in data
group d by d.Foo
into grp
select new {
Foo = grp.Key,
Bars = grp.Select(d2 => d2.Bar).ToArray()
};
// find the total number of (data) rows
int rows = grps.Max(grp => grp.Bars.Length);
// output columns
foreach (var grp in grps) {
Console.Write(grp.Foo + "\t");
}
Console.WriteLine();
// output data
for (int i = 0; i < rows; i++) {
foreach (var grp in grps) {
Console.Write((i < grp.Bars.Length ? grp.Bars[i] : null) + "\t");
}
Console.WriteLine();
}
Marc's answer gives sparse matrix that can't be pumped into Grid directly.
I tried to expand the code from the link provided by Vasu as below:
public static Dictionary<TKey1, Dictionary<TKey2, TValue>> Pivot3<TSource, TKey1, TKey2, TValue>(
this IEnumerable<TSource> source
, Func<TSource, TKey1> key1Selector
, Func<TSource, TKey2> key2Selector
, Func<IEnumerable<TSource>, TValue> aggregate)
{
return source.GroupBy(key1Selector).Select(
x => new
{
X = x.Key,
Y = source.GroupBy(key2Selector).Select(
z => new
{
Z = z.Key,
V = aggregate(from item in source
where key1Selector(item).Equals(x.Key)
&& key2Selector(item).Equals(z.Key)
select item
)
}
).ToDictionary(e => e.Z, o => o.V)
}
).ToDictionary(e => e.X, o => o.Y);
}
internal class Employee
{
public string Name { get; set; }
public string Department { get; set; }
public string Function { get; set; }
public decimal Salary { get; set; }
}
public void TestLinqExtenions()
{
var l = new List<Employee>() {
new Employee() { Name = "Fons", Department = "R&D", Function = "Trainer", Salary = 2000 },
new Employee() { Name = "Jim", Department = "R&D", Function = "Trainer", Salary = 3000 },
new Employee() { Name = "Ellen", Department = "Dev", Function = "Developer", Salary = 4000 },
new Employee() { Name = "Mike", Department = "Dev", Function = "Consultant", Salary = 5000 },
new Employee() { Name = "Jack", Department = "R&D", Function = "Developer", Salary = 6000 },
new Employee() { Name = "Demy", Department = "Dev", Function = "Consultant", Salary = 2000 }};
var result5 = l.Pivot3(emp => emp.Department, emp2 => emp2.Function, lst => lst.Sum(emp => emp.Salary));
var result6 = l.Pivot3(emp => emp.Function, emp2 => emp2.Department, lst => lst.Count());
}
* can't say anything about the performance though.
You can use Linq's .ToLookup to group in the manner you are looking for.
var lookup = data.ToLookup(d => d.TypeCode, d => d.User);
Then it's a matter of putting it into a form that your consumer can make sense of. For instance:
//Warning: untested code
var enumerators = lookup.Select(g => g.GetEnumerator()).ToList();
int columns = enumerators.Count;
while(columns > 0)
{
for(int i = 0; i < enumerators.Count; ++i)
{
var enumerator = enumerators[i];
if(enumator == null) continue;
if(!enumerator.MoveNext())
{
--columns;
enumerators[i] = null;
}
}
yield return enumerators.Select(e => (e != null) ? e.Current : null);
}
Put that in an IEnumerable<> method and it will (probably) return a collection (rows) of collections (column) of User where a null is put in a column that has no data.
I guess this is similar to Marc's answer, but I'll post it since I spent some time working on it. The results are separated by " | " as in your example. It also uses the IGrouping<int, string> type returned from the LINQ query when using a group by instead of constructing a new anonymous type. This is tested, working code.
var Items = new[] {
new { TypeCode = 1, UserName = "Don Smith"},
new { TypeCode = 1, UserName = "Mike Jones"},
new { TypeCode = 1, UserName = "James Ray"},
new { TypeCode = 2, UserName = "Tom Rizzo"},
new { TypeCode = 2, UserName = "Alex Homes"},
new { TypeCode = 3, UserName = "Andy Bates"}
};
var Columns = from i in Items
group i.UserName by i.TypeCode;
Dictionary<int, List<string>> Rows = new Dictionary<int, List<string>>();
int RowCount = Columns.Max(g => g.Count());
for (int i = 0; i <= RowCount; i++) // Row 0 is the header row.
{
Rows.Add(i, new List<string>());
}
int RowIndex;
foreach (IGrouping<int, string> c in Columns)
{
Rows[0].Add(c.Key.ToString());
RowIndex = 1;
foreach (string user in c)
{
Rows[RowIndex].Add(user);
RowIndex++;
}
for (int r = RowIndex; r <= Columns.Count(); r++)
{
Rows[r].Add(string.Empty);
}
}
foreach (List<string> row in Rows.Values)
{
Console.WriteLine(row.Aggregate((current, next) => current + " | " + next));
}
Console.ReadLine();
I also tested it with this input:
var Items = new[] {
new { TypeCode = 1, UserName = "Don Smith"},
new { TypeCode = 3, UserName = "Mike Jones"},
new { TypeCode = 3, UserName = "James Ray"},
new { TypeCode = 2, UserName = "Tom Rizzo"},
new { TypeCode = 2, UserName = "Alex Homes"},
new { TypeCode = 3, UserName = "Andy Bates"}
};
Which produced the following results showing that the first column doesn't need to contain the longest list. You could use OrderBy to get the columns ordered by TypeCode if needed.
1 | 3 | 2
Don Smith | Mike Jones | Tom Rizzo
| James Ray | Alex Homes
| Andy Bates |
#Sanjaya.Tio I was intrigued by your answer and created this adaptation which minimizes keySelector execution. (untested)
public static Dictionary<TKey1, Dictionary<TKey2, TValue>> Pivot3<TSource, TKey1, TKey2, TValue>(
this IEnumerable<TSource> source
, Func<TSource, TKey1> key1Selector
, Func<TSource, TKey2> key2Selector
, Func<IEnumerable<TSource>, TValue> aggregate)
{
var lookup = source.ToLookup(x => new {Key1 = key1Selector(x), Key2 = key2Selector(x)});
List<TKey1> key1s = lookup.Select(g => g.Key.Key1).Distinct().ToList();
List<TKey2> key2s = lookup.Select(g => g.Key.Key2).Distinct().ToList();
var resultQuery =
from key1 in key1s
from key2 in key2s
let lookupKey = new {Key1 = key1, Key2 = key2}
let g = lookup[lookupKey]
let resultValue = g.Any() ? aggregate(g) : default(TValue)
select new {Key1 = key1, Key2 = key2, ResultValue = resultValue};
Dictionary<TKey1, Dictionary<TKey2, TValue>> result = new Dictionary<TKey1, Dictionary<TKey2, TValue>>();
foreach(var resultItem in resultQuery)
{
TKey1 key1 = resultItem.Key1;
TKey2 key2 = resultItem.Key2;
TValue resultValue = resultItem.ResultValue;
if (!result.ContainsKey(key1))
{
result[key1] = new Dictionary<TKey2, TValue>();
}
var subDictionary = result[key1];
subDictionary[key2] = resultValue;
}
return result;
}
I have 2 objects (lists loaded from XML) report and database (showed bellow in code) and i should analyse them and mark items with 0, 1, 2, 3 according to some conditions
TransactionResultCode = 0; // SUCCESS (all fields are equivalents: [Id, AccountNumber, Date, Amount])
TransactionResultCode = 1; // Exists in report but Not in database
TransactionResultCode = 2; // Exists in database but Not in report
TransactionResultCode = 3; // Field [Id] are equals but other fields [AccountNumber, Date, Amount] are different.
I'll be happy if somebody could found time to suggest how to optimize some queries.
Bellow is the code:
THANK YOU!!!
//TransactionResultCode = 0 - SUCCESS
//JOIN on all fields
var result0 = from d in database
from r in report
where (d.TransactionId == r.MovementID) &&
(d.TransactionAccountNumber == long.Parse(r.AccountNumber)) &&
(d.TransactionDate == r.MovementDate) &&
(d.TransactionAmount == r.Amount)
orderby d.TransactionId
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount,
TransactionResultCode = 0
};
//*******************************************
//JOIN on [Id] field
var joinedList = from d in database
from r in report
where d.TransactionId == r.MovementID
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount
};
//Difference report - database
var onlyReportID = report.Select(r => r.MovementID).Except(joinedList.Select(d => d.TransactionId));
//TransactionResultCode = 1 - Not Found in database
var result1 = from o in onlyReportID
from r in report
where (o == r.MovementID)
orderby r.MovementID
select new TransactionList()
{
TransactionId = r.MovementID,
TransactionAccountNumber = long.Parse(r.AccountNumber),
TransactionDate = r.MovementDate,
TransactionAmount = r.Amount,
TransactionResultCode = 1
};
//*******************************************
//Difference database - report
var onlyDatabaseID = database.Select(d => d.TransactionId).Except(joinedList.Select(d => d.TransactionId));
//TransactionResultCode = 2 - Not Found in report
var result2 = from o in onlyDatabaseID
from d in database
where (o == d.TransactionId)
orderby d.TransactionId
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount,
TransactionResultCode = 2
};
//*******************************************
var qwe = joinedList.Select(j => j.TransactionId).Except(result0.Select(r => r.TransactionId));
//TransactionResultCode = 3 - Transaction Results are different (Amount, AccountNumber, Date, )
var result3 = from j in joinedList
from q in qwe
where j.TransactionId == q
select new TransactionList()
{
TransactionId = j.TransactionId,
TransactionAccountNumber = j.TransactionAccountNumber,
TransactionDate = j.TransactionDate,
TransactionAmount = j.TransactionAmount,
TransactionResultCode = 3
};
you may try something like below:
public void Test()
{
var report = new[] {new Item(1, "foo", "boo"), new Item(2, "foo2", "boo2"), new Item(3, "foo3", "boo3")};
var dataBase = new[] {new Item(1, "foo", "boo"), new Item(2, "foo22", "boo2"), new Item(4, "txt", "rt")};
Func<Item, bool> inBothLists = (i) => report.Contains(i) && dataBase.Contains(i);
Func<IEnumerable<Item>, Item, bool> containsWithID = (e, i) => e.Select(_ => _.ID).Contains(i.ID);
Func<Item, int> getCode = i =>
{
if (inBothLists(i))
{
return 0;
}
if(containsWithID(report, i) && containsWithID(dataBase, i))
{
return 3;
}
if (report.Contains(i))
{
return 2;
}
else return 1;
};
var result = (from item in dataBase.Union(report) select new {Code = getCode(item), Item = item}).Distinct();
}
public class Item
{
// You need also to override Equals() and GetHashCode().. I omitted them to save space
public Item(int id, string text1, string text2)
{
ID = id;
Text1 = text1;
Text2 = text2;
}
public int ID { get; set; }
public string Text1 { get; set; }
public string Text2 { get; set; }
}
Note that you need to either implement Equals() for you items, or implement an IEqualityComparer<> and feed it to Contains() methods.
.NET 4, I have
public class Humi
{
public int huKey { get; set; }
public string huVal { get; set; }
}
And in another class is this code in a method:
IEnumerable<Humi> someHumi = new List<Humi>(); //This is actually ISingleResult that comes from a LinqToSql-fronted sproc but I don't think is relevant for my question
var humia = new Humi { huKey = 1 , huVal = "a"};
var humib = new Humi { huKey = 1 , huVal = "b" };
var humic = new Humi { huKey = 2 , huVal = "c" };
var humid = new Humi { huKey = 2 , huVal = "d" };
I want to create a single IDictionary <int,string[]>
with key 1 containing ["a","b"] and key 2 containing ["c","d"]
Can anyone point out a decent way to to that conversion with Linq?
Thanks.
var myDict = someHumi
.GroupBy(h => h.huKey)
.ToDictionary(
g => g.Key,
g => g.ToArray())
Create an IEnumerable<IGrouping<int, Humi>> and then project that into a dictionary. Note .ToDictionary returns a Dictionary, not an IDictionary.
You can use ToLookup() which allows each key to hold multiple values, exactly your scenario (note that each key would hold an IEnumerable<string> of values though not an array):
var myLookup = someHumi.ToLookup(x => x.huKey, x => x.huVal);
foreach (var item in myLookup)
{
Console.WriteLine("{0} contains: {1}", item.Key, string.Join(",", item));
}
Output:
1 contains: a,b
2 contains: c,d