{"id":12744,"date":"2024-03-14T16:32:23","date_gmt":"2024-03-14T16:32:23","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-is-the-groupby-function-used-in-c\/"},"modified":"2025-08-05T06:14:24","modified_gmt":"2025-08-05T06:14:24","slug":"how-is-the-groupby-function-used-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-is-the-groupby-function-used-in-c\/","title":{"rendered":"C# GroupBy: How to Use"},"content":{"rendered":"<p>In C#, the GroupBy method is used to group elements in a collection based on a specific key. It returns an IEnumerable<IGrouping<TKey, TElement>> object containing the grouped results, where TKey is the type of the key for the grouping and TElement is the type of the elements in the collection.<\/p>\n<p>The GroupBy method has multiple overload forms, with the most common form taking a Func<TSource, TKey> parameter that defines the selector function for grouping keys. For example, the following example groups a collection of strings by their length.<\/p>\n<pre class=\"post-pre\"><code>List&lt;<span class=\"hljs-built_in\">string<\/span>&gt; strings = <span class=\"hljs-keyword\">new<\/span> List&lt;<span class=\"hljs-built_in\">string<\/span>&gt; { <span class=\"hljs-string\">\"apple\"<\/span>, <span class=\"hljs-string\">\"banana\"<\/span>, <span class=\"hljs-string\">\"orange\"<\/span>, <span class=\"hljs-string\">\"pear\"<\/span>, <span class=\"hljs-string\">\"grape\"<\/span> };\r\n\r\n<span class=\"hljs-keyword\">var<\/span> groups = strings.GroupBy(s =&gt; s.Length);\r\n\r\n<span class=\"hljs-keyword\">foreach<\/span> (<span class=\"hljs-keyword\">var<\/span> <span class=\"hljs-keyword\">group<\/span> <span class=\"hljs-keyword\">in<\/span> groups)\r\n{\r\n    Console.WriteLine(<span class=\"hljs-string\">$\"Group key: <span class=\"hljs-subst\">{<span class=\"hljs-keyword\">group<\/span>.Key}<\/span>\"<\/span>);\r\n    <span class=\"hljs-keyword\">foreach<\/span> (<span class=\"hljs-keyword\">var<\/span> element <span class=\"hljs-keyword\">in<\/span> <span class=\"hljs-keyword\">group<\/span>)\r\n    {\r\n        Console.WriteLine(<span class=\"hljs-string\">$\"Element: <span class=\"hljs-subst\">{element}<\/span>\"<\/span>);\r\n    }\r\n    Console.WriteLine();\r\n}\r\n<\/code><\/pre>\n<p>Output:<\/p>\n<pre class=\"post-pre\"><code>Group key: 5\r\nElement: apple\r\nElement: grape\r\n\r\nGroup key: 6\r\nElement: banana\r\n\r\nGroup key: 6\r\nElement: orange\r\n\r\nGroup key: 4\r\nElement: pear\r\n<\/code><\/pre>\n<p>In the above example, the strings.GroupBy(s => s.Length) method groups a collection of strings based on their length and returns an IEnumerable<IGrouping<int, string>> object with 4 groups. Each group has a key (the length of the strings) that can be accessed using group.Key. Each group is an iterable collection that can be accessed using group.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C#, the GroupBy method is used to group elements in a collection based on a specific key. It returns an IEnumerable object containing the grouped results, where TKey is the type of the key for the grouping and TElement is the type of the elements in the collection. The GroupBy method has multiple overload [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[274,4740,450,9600,4170],"class_list":["post-12744","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c","tag-c-collections","tag-c-tutorial","tag-groupby","tag-linq"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>C# GroupBy: How to Use - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn to group collection elements in C# with the GroupBy method. 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