Linq query: Group by Multiple Columns - linq

Question

I have a list that looks like this.
-100 Smith, Jane $1000
-100 Smith, John $1100.00
-100 Smith, Cole $840.00
-110 Jones, Harry $1270.00
-110 Jones, Diane $870.00
-111 Jones, Richard $1560.00
Using LINQ, I wish to write a query that will allow me to SUM up the values by family.
The first identifier is the family id.
For the above set of records, my output will look like:
-100 Smith $2940.00
-110 Jones $2140.00
-111 Jones $1560.00
Here's my code:
static void Main(string[] args)
{
_fi = FillIncome();
var query = (from f in _fi group f by f.familyId into delta select new {familyId = delta.Key, amount = delta.Sum(x => x.income) });
foreach (var q in query)
{
Console.WriteLine(q);
}}
static List<FamilyIncome> FillIncome()
{
var income = new List<FamilyIncome>();
var fi = new FamilyIncome {familyId = -100, lastname = "Smith", firstname = "Jane", income = 1000};
income.Add(fi);
fi = new FamilyIncome { familyId = -100, lastname = "Smith", firstname = "John", income = 1100 };
income.Add(fi);
fi = new FamilyIncome { familyId = -100, lastname = "Smith", firstname = "Cole", income = 840 };
income.Add(fi);
fi = new FamilyIncome { familyId = -110, lastname = "Jones", firstname = "Harry", income = 1270 };
income.Add(fi);
fi = new FamilyIncome { familyId = -110, lastname = "Jones", firstname = "Diane", income = 970 };
income.Add(fi);
fi = new FamilyIncome { familyId = -111, lastname = "Jones", firstname = "Richard", income = 1600 };
income.Add(fi);
return income;
}

Answer 1

Let's assume the class representing your data item looks like this:
class DataItem
{
public int FamilyId { get; set; }
public string FamilyName { get; set; }
public string FirstName { get; set; }
public decimal Salary { get; set; }
}
Then your data should be presented as
private static DataItem[] items = new[]
{
new DataItem { FamilyId = -100, FamilyName = "Smith", FirstName = "Jane", Salary = 1000},
new DataItem { FamilyId = -100, FamilyName = "Smith", FirstName = "John", Salary = 1100},
new DataItem { FamilyId = -100, FamilyName = "Smith", FirstName = "Cole", Salary = 840},
new DataItem { FamilyId = -110, FamilyName = "Jones", FirstName = "Harry", Salary = 1270},
new DataItem { FamilyId = -110, FamilyName = "Jones", FirstName = "Diane", Salary = 870},
new DataItem {FamilyId = -111, FamilyName = "Jones", FirstName = "Richard", Salary = 1560},
};
The query producing the desired output will be the following:
var groupedItems =
from item in items
group item by new {item.FamilyId, item.FamilyName}
into family
select new {family.Key.FamilyId, family.Key.FamilyName, Sum = family.Sum(item => item.Salary)};
And to output these grouped items you can use something like
foreach (var groupedItem in groupedItems)
{
Console.WriteLine(
"{0}\t{1}\t{2}",
groupedItem.FamilyId,
groupedItem.FamilyName,
groupedItem.Sum);
}
Hope this helps