{"id":13646,"date":"2024-03-15T07:32:50","date_gmt":"2024-03-15T07:32:50","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-is-the-where-keyword-used-in-c\/"},"modified":"2025-08-05T21:31:37","modified_gmt":"2025-08-05T21:31:37","slug":"how-is-the-where-keyword-used-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-is-the-where-keyword-used-in-c\/","title":{"rendered":"C# Where Keyword: LINQ Filtering Guide"},"content":{"rendered":"<p>In C#, the &#8220;where&#8221; keyword is used in LINQ queries to specify one or more filtering conditions. It can be used to filter elements in a collection, returning only those that meet the specified criteria.<\/p>\n<p>The basic syntax of the &#8220;where&#8221; keyword is:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">var<\/span> result = <span class=\"hljs-keyword\">from<\/span> item <span class=\"hljs-keyword\">in<\/span> collection\r\n             <span class=\"hljs-keyword\">where<\/span> condition\r\n             <span class=\"hljs-keyword\">select<\/span> item;\r\n<\/code><\/pre>\n<p>Or, alternatively, use the method syntax.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">var<\/span> result = collection.Where(item =&gt; condition);\r\n<\/code><\/pre>\n<p>In this case, item represents each element in the set, and condition is a Boolean expression used for filtering elements.<\/p>\n<p>Here are some examples of using &#8220;where&#8221;:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-comment\">\/\/ \u4ece\u6574\u6570\u96c6\u5408\u4e2d\u7b5b\u9009\u51fa\u5927\u4e8e5\u7684\u5143\u7d20<\/span>\r\n<span class=\"hljs-keyword\">var<\/span> numbers = <span class=\"hljs-keyword\">new<\/span> List&lt;<span class=\"hljs-built_in\">int<\/span>&gt; { <span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>, <span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>, <span class=\"hljs-number\">5<\/span>, <span class=\"hljs-number\">6<\/span>, <span class=\"hljs-number\">7<\/span>, <span class=\"hljs-number\">8<\/span>, <span class=\"hljs-number\">9<\/span>, <span class=\"hljs-number\">10<\/span> };\r\n<span class=\"hljs-keyword\">var<\/span> result = numbers.Where(n =&gt; n &gt; <span class=\"hljs-number\">5<\/span>);\r\n\r\n<span class=\"hljs-comment\">\/\/ \u4ece\u5b57\u7b26\u4e32\u6570\u7ec4\u4e2d\u7b5b\u9009\u51fa\u957f\u5ea6\u5927\u4e8e\u7b49\u4e8e5\u4e14\u4ee5\u5927\u5199\u5b57\u6bcd\u5f00\u5934\u7684\u5b57\u7b26\u4e32<\/span>\r\n<span class=\"hljs-keyword\">var<\/span> strings = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-built_in\">string<\/span>[] { <span class=\"hljs-string\">\"Apple\"<\/span>, <span class=\"hljs-string\">\"banana\"<\/span>, <span class=\"hljs-string\">\"cherry\"<\/span>, <span class=\"hljs-string\">\"Orange\"<\/span>, <span class=\"hljs-string\">\"grape\"<\/span> };\r\n<span class=\"hljs-keyword\">var<\/span> result = strings.Where(s =&gt; s.Length &gt;= <span class=\"hljs-number\">5<\/span> &amp;&amp; <span class=\"hljs-built_in\">char<\/span>.IsUpper(s[<span class=\"hljs-number\">0<\/span>]));\r\n\r\n<span class=\"hljs-comment\">\/\/ \u4ece\u81ea\u5b9a\u4e49\u5bf9\u8c61\u96c6\u5408\u4e2d\u7b5b\u9009\u51fa\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6\u7684\u5bf9\u8c61<\/span>\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Person<\/span>\r\n{\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-built_in\">string<\/span> Name { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-built_in\">int<\/span> Age { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\r\n}\r\n\r\n<span class=\"hljs-keyword\">var<\/span> people = <span class=\"hljs-keyword\">new<\/span> List&lt;Person&gt;\r\n{\r\n    <span class=\"hljs-keyword\">new<\/span> Person { Name = <span class=\"hljs-string\">\"Alice\"<\/span>, Age = <span class=\"hljs-number\">25<\/span> },\r\n    <span class=\"hljs-keyword\">new<\/span> Person { Name = <span class=\"hljs-string\">\"Bob\"<\/span>, Age = <span class=\"hljs-number\">30<\/span> },\r\n    <span class=\"hljs-keyword\">new<\/span> Person { Name = <span class=\"hljs-string\">\"Charlie\"<\/span>, Age = <span class=\"hljs-number\">35<\/span> }\r\n};\r\n\r\n<span class=\"hljs-keyword\">var<\/span> result = people.Where(p =&gt; p.Age &gt; <span class=\"hljs-number\">30<\/span>);\r\n<\/code><\/pre>\n<p>In these examples, the &#8216;where&#8217; keyword is used to filter out elements that meet specific conditions and place them into a new collection.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C#, the &#8220;where&#8221; keyword is used in LINQ queries to specify one or more filtering conditions. It can be used to filter elements in a collection, returning only those that meet the specified criteria. The basic syntax of the &#8220;where&#8221; keyword is: var result = from item in collection where condition select item; Or, [&hellip;]<\/p>\n","protected":false},"author":9,"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":[274,536,367,4170,18223],"class_list":["post-13646","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c","tag-collections","tag-filtering","tag-linq","tag-where-keyword"],"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# Where Keyword: LINQ Filtering Guide - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to use the C# where keyword in LINQ queries for filtering collections. 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