Grouping Operators in LINQ
The operators put data into some groups based on a common shared attribute.
Operator | Description | C# Query Expression Syntax | VB Query Expression Syntax |
---|---|---|---|
GroupBy | Organize a sequence of items in groups and return them as an IEnumerable collection of type IGrouping<key, element> | group … by -or- group … by … into … | Group … By … Into … |
ToLookup | Execute a grouping operation in which a sequence of key pairs are returned | Not Applicable | Not Applicable |
Example of GroupBy - Query Expression
C#
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Operators { class Program { static void Main(string[] args) { List<int> numbers = new List<int>() { 35, 44, 200, 84, 3987, 4, 199, 329, 446, 208 }; IEnumerable<IGrouping<int, int>> query = from number in numbers group number by number % 2; foreach (var group in query) { Console.WriteLine(group.Key == 0 ? "\nEven numbers:" : "\nOdd numbers:"); foreach (int i in group) Console.WriteLine(i); } Console.ReadLine(); } } }
VB
Module Module1 Sub Main() Dim numbers As New System.Collections.Generic.List(Of Integer)( New Integer() {35, 44, 200, 84, 3987, 4, 199, 329, 446, 208}) Dim query = From number In numbers Group By Remainder = (number Mod 2) Into Group For Each group In query Console.WriteLine(If(group.Remainder = 0, vbCrLf &"Even numbers:", vbCrLf &"Odd numbers:")) For Each num In group.Group Console.WriteLine(num) Next Next Console.ReadLine() End Sub End Module
When the above code in C# or VB is compiled and executed, it produces the following result −
Odd numbers: 35 3987 199 329 Even numbers: 44 200 84 4 446 208
linq_query_operators.htm
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