C# LINQ

Question

I know its easy to group objects by two properties but I was wondering is it possible to Group by either of two properties? Probably below example will make it more clear:-
Suppose I have this table:-

Now, i want to group this data either if CategoryIds are same or Fruits are same.
Sample Output:-
Group 1:-
1 Apple
1 Grapes
Group 2:-
2 Tablet
2 Laptop
Group 3:-
5 Coke6 Coke

CategoryID	Fruits
1	Apple
1	Grapes
2	Tablet
2	Laptop
5	Coke
6	Coke

Lawrence Pond · Answer

Hello Friends Here is a option that show how to group by either category or fruits Also notice the I change the order of the items on the initial load to show the grouping and results were done correctly Linq is so very powerful I am learning a lot and appreciate the support I receive here on questions I hope this helps you and others Notice the code is only a single line two lines to show both methods using dot notation void main() { var myItemList = new[] { new item { category =2 fruit=Tablet} new item { category =1 fruit=Apple} new item { category=6 fruit=Coke} new item { category=2 fruit=Laptop} new item { category =5 fruit=Coke} new item { category=1 fruit=Grapes} }; var myItemsGroupedByCategory = myItemList.GroupBy(p=>new{CATEGORY=p.category}).Select(p=>new{Category=p.Key.CATEGORY Fruit =p.ToList() ItemsInGroup =p.Count()}).OrderBy (p =>p.Category ); var myItemsGroupedByFruit = myItemList.GroupBy(p=>new{FRUIT= p.fruit}).Select(p=>new{Fruit =p.Key.FRUIT Category =p.ToList() ItemsInGroup =p.Count()}).OrderBy (p =>p.Fruit); } public class item { public int category { get; set; } public string fruit { get; set; } } RESULTS ORDER BY CATEGORY GCAT Cat/Fruit ItemsInGroup 1 2 1 Apple 1 Grapes 2 2 2 Tablet 2 Laptop 5 1 5 Coke 6 1 6 Coke ORDER BY FRUIT Fruit Cat/Fruit ItemsInGroup Apple 1 1 Apple Coke 2 6 Coke 5 Coke Grapes 1 1 Grapes LapTop 1 2 Laptop Tablet 1 2 Tablet

Saber Shaikh · Answer

Send Me Select query in SQL I will make in LINQ My Blog : http://aspnettutorialscode.blogspot.in/ Thank You

Rahul Singh · Answer

Thanks Saber. But that is not what I am expecting re-read my question.

Saber Shaikh · Answer

Try This var Result = from p in db.tbl_name group p by p.CategoryID into g select new { CategoryID= g.Key Fruits };

Vulpes · Answer

OK I've had another look at it and managed to do it as a LINQ query by creating a custom IEqualityComparer: using System; using System.Collections.Generic; using System.Linq; class Item { public int CategoryID {get; set;} public string Fruits {get; set; } public Item(int cat string fruit) { CategoryID = cat; Fruits = fruit; } public override string ToString() { return String.Format({0} : {1} CategoryID Fruits); } } class ItemComparer : IEqualityComparer { public bool Equals(Item i1 Item i2) { if((i1.CategoryID == i2.CategoryID) || (i1.Fruits == i2.Fruits)) return true; return false; } public int GetHashCode(Item i) { return 1; } } class Program { static void Main() { var item1 = new Item(1 Apple); var item2 = new Item(1 Grapes); var item3 = new Item(2 Tablet); var item4 = new Item(2 Laptop); var item5 = new Item(5 Coke); var item6 = new Item(6 Coke); var items = new List {item1 item2 item3 item4 item5 item6}; var groups = items.GroupBy(i => i new ItemComparer()); // print results int num = 1; foreach(var g in groups) { Console.WriteLine(Group {0}:- num); foreach(Item item in g) Console.WriteLine(item); num++; Console.WriteLine(); } Console.ReadKey(); } } The outputas before is : Group 1:- 1 : Apple 1 : Grapes Group 2:- 2 : Tablet 2 : Laptop Group 3:- 5 : Coke 6 : Coke However I'm not very happy with the GetHashCode() implementation as I could only ensure that equal instances had the same hash code by returning the same constant for all instances This is because there's no way of telling in advance whether the CustomerID or the Fruits property will be used to test for equality and so you can't use those in the calculation. As the GroupBy extension method creates a dictionary of lists internally the hash code is relevant and whilst it doesn't matter for a handful of objects it would matter if you had thousands. Another point that has struck me is that the grouping may depend on the order in which the items are added to the list which again isn't very satisfactory.

Rahul Singh · Answer

Thanks Vulpes! But I was looking for a LINQ query because this is just a part of my problem and i wanted to add this LINQ to the primary LINQ query.

Vulpes · Answer

I couldn't figure out an efficient way to do this using LINQ but if you don't get a better answer here's how you could do it using 'traditional' code: using System; using System.Collections.Generic; class Item { public int CategoryID {get; set;} public string Fruits {get; set; } public Item(int cat string fruit) { CategoryID = cat; Fruits = fruit; } public override string ToString() { return String.Format({0} : {1} CategoryID Fruits); } } class Program { static void Main() { var item1 = new Item(1 Apple); var item2 = new Item(1 Grapes); var item3 = new Item(2 Tablet); var item4 = new Item(2 Laptop); var item5 = new Item(5 Coke); var item6 = new Item(6 Coke); var items = new List {item1 item2 item3 item4 item5 item6}; var groups = new List >(); var group = new List (); group.Add(items[0]); groups.Add(group); for(int i = 1; i { bool newGroup = true; foreach(List g in groups) { foreach(Item item in g) { if ((items[i].CategoryID == item.CategoryID) || (items[i].Fruits == item.Fruits)) { g.Add(items[i]); newGroup = false; break; } } if(!newGroup) break; } if(newGroup) { group = new List (); group.Add(items[i]); groups.Add(group); } } // print results int num = 1; foreach(List g in groups) { Console.WriteLine(Group {0}:- num); foreach(Item item in g) Console.WriteLine(item); num++; Console.WriteLine(); } Console.ReadKey(); } } The output is: Group 1:- 1 : Apple 1 : Grapes Group 2:- 2 : Tablet 2 : Laptop Group 3:- 5 : Coke 6 : Coke