{"id":1087,"date":"2023-03-19T10:38:58","date_gmt":"2023-03-19T03:38:58","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1087"},"modified":"2023-06-26T15:25:22","modified_gmt":"2023-06-26T08:25:22","slug":"linq-thenbydescending","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-linq\/linq-thenbydescending\/","title":{"rendered":"LINQ ThenByDescending"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn how to use the LINQ <code>ThenByDescending()<\/code> method to sort a sequence in descending order based on a secondary key.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Introduction to the LINQ ThenByDescending() method<\/h2>\n\n\n\n<p>The LINQ <code>ThenByDescending()<\/code> method sorts a sequence in descending order based on a secondary key after the sequence has been sorted by a primary key using either <code><a href=\"https:\/\/csharptutorial.net\/csharp-linq\/linq-orderby\/\">OrderBy()<\/a><\/code> or <code><a href=\"https:\/\/csharptutorial.net\/csharp-linq\/linq-orderbydescending\/\">OrderByDescending()<\/a><\/code> method.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> IOrderedEnumerable&lt;TSource&gt; ThenByDescending&lt;TSource, TKey&gt; (\n    <span class=\"hljs-keyword\">this<\/span> IOrderedEnumerable&lt;TSource&gt; source, \n    Func&lt;TSource, TKey&gt; keySelector\n);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>In this syntax:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>TSource<\/code> is the type of elements in the <code>source<\/code> sequence.<\/li>\n\n\n\n<li><code>TKey<\/code> is the type of sort key.<\/li>\n\n\n\n<li><code>source<\/code> is the input sequence to sort.<\/li>\n\n\n\n<li><code>keySelector<\/code> is a function that selects a key to sort the <code>source<\/code> sequence.<\/li>\n<\/ul>\n\n\n\n<p>The <code>ThenByDescending()<\/code> method returns a new sequence sorted by a key in descending order. The type of resulting sequence is an <code>IOrderedEnumerable&lt;TElement&gt;<\/code>.<\/p>\n\n\n\n<p>If the source or <code>keySelector<\/code> is null, the method <code>ThenByDescending()<\/code> method will throw an <code>ArgumentNullException<\/code>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">LINQ ThenByDescending() method example<\/h2>\n\n\n\n<p>The following program uses the <code><a href=\"https:\/\/csharptutorial.net\/csharp-linq\/linq-orderbydescending\/\">OrderByDesending()<\/a><\/code> method to sort a list of employees by departments in descending order first and then uses the <code>ThenByDescending()<\/code> method to sort the employees in each department by <code>Salary<\/code> from high to low:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">using<\/span> <span class=\"hljs-keyword\">static<\/span> System.Console;\n\n<span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Employee<\/span>\n{\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">string<\/span>? Name { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">string<\/span>? Department { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">int<\/span> Salary { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n}\n<span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Program<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Main<\/span>(<span class=\"hljs-params\"><\/span>)<\/span>\n    {\n        <span class=\"hljs-keyword\">var<\/span> employees = <span class=\"hljs-keyword\">new<\/span> List&lt;Employee&gt;()\n        {\n            <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"John\"<\/span>, Department = <span class=\"hljs-string\">\"HR\"<\/span>, Salary = <span class=\"hljs-number\">50000<\/span> },\n            <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Jane\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">60000<\/span> },\n            <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Bob\"<\/span>, Department = <span class=\"hljs-string\">\"HR\"<\/span>, Salary = <span class=\"hljs-number\">45000<\/span> },\n            <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Sara\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">55000<\/span> },\n            <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Tom\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">65000<\/span> }\n        };\n\n        <span class=\"hljs-keyword\">var<\/span> results = employees.OrderByDescending(e =&gt; e.Department)\n                               .ThenByDescending(e =&gt; e.Salary);\n\n        <span class=\"hljs-keyword\">foreach<\/span> (<span class=\"hljs-keyword\">var<\/span> e <span class=\"hljs-keyword\">in<\/span> results)\n        {\n            WriteLine(<span class=\"hljs-string\">$\"<span class=\"hljs-subst\">{e.Department}<\/span> - <span class=\"hljs-subst\">{e.Name}<\/span> - <span class=\"hljs-subst\">{e.Salary:C}<\/span>\"<\/span>);\n        }\n    }\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Output:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\">IT - Tom - $<span class=\"hljs-number\">65<\/span>,<span class=\"hljs-number\">000.00<\/span>\nIT - Jane - $<span class=\"hljs-number\">60<\/span>,<span class=\"hljs-number\">000.00<\/span>\nIT - Sara - $<span class=\"hljs-number\">55<\/span>,<span class=\"hljs-number\">000.00<\/span>\nHR - John - $<span class=\"hljs-number\">50<\/span>,<span class=\"hljs-number\">000.00<\/span>\nHR - Bob - $<span class=\"hljs-number\">45<\/span>,<span class=\"hljs-number\">000.00<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>How it works.<\/p>\n\n\n\n<p>First, define the <code>Employee<\/code> class that has three properties: <code>Name<\/code>, <code>Department<\/code>, and <code>Salary<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Employee<\/span>\n{\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">string<\/span>? Name { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">string<\/span>? Department { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">int<\/span> Salary { <span class=\"hljs-keyword\">get<\/span>; <span class=\"hljs-keyword\">set<\/span>; }\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, create a new list that has five <code>Employee<\/code> objects:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">var<\/span> employees = <span class=\"hljs-keyword\">new<\/span> List&lt;Employee&gt;() \n{\n    <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"John\"<\/span>, Department = <span class=\"hljs-string\">\"HR\"<\/span>, Salary = <span class=\"hljs-number\">50000<\/span> },\n    <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Jane\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">60000<\/span> },\n    <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Bob\"<\/span>, Department = <span class=\"hljs-string\">\"HR\"<\/span>, Salary = <span class=\"hljs-number\">45000<\/span> },\n    <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Sara\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">55000<\/span> },\n    <span class=\"hljs-keyword\">new<\/span> Employee { Name = <span class=\"hljs-string\">\"Tom\"<\/span>, Department = <span class=\"hljs-string\">\"IT\"<\/span>, Salary = <span class=\"hljs-number\">65000<\/span> }\n};<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Third, sort the <code>Employee<\/code> objects by departments in descending order using the <code>OrderByDescendig<\/code> method and then sort the <code>Employee<\/code> objects in each department by salary using the <code>ThenByDescending()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-6\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">var<\/span> results = employees.OrderByDescending(e =&gt; e.Department)\n                       .ThenByDescending(e =&gt; e.Salary);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-6\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Finally, write the employees to the console using a <code>foreach<\/code> and <code>WriteLine()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-7\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">foreach<\/span> (<span class=\"hljs-keyword\">var<\/span> e <span class=\"hljs-keyword\">in<\/span> results)\n{\n    WriteLine(<span class=\"hljs-string\">$\"<span class=\"hljs-subst\">{e.Department}<\/span> - <span class=\"hljs-subst\">{e.Name}<\/span> - <span class=\"hljs-subst\">{e.Salary:C}<\/span>\"<\/span>);\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-7\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<h2 class=\"wp-block-heading\">Summary<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Use LINQ <code>ThenByDescending()<\/code> method to sort elements in a sequence in descending order by a secondary key, after the sequence has been sorted by a primary key.<\/li>\n<\/ul>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this tutorial helpful ?<\/div>\n\t\t<div class=\"wth-thumbs\">\n\t\t\t<button\n\t\t\t\tdata-post=\"1087\"\n\t\t\t\tdata-post-url=\"https:\/\/www.csharptutorial.net\/csharp-linq\/linq-thenbydescending\/\"\n\t\t\t\tdata-post-title=\"LINQ ThenByDescending\"\n\t\t\t\tdata-response=\"1\"\n\t\t\t\tclass=\"wth-btn-rounded wth-yes-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t\tclass=\"feather feather-thumbs-up block w-full h-full\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M14 9V5a3 3 0 0 0-3-3l-4 9v11h11.28a2 2 0 0 0 2-1.7l1.38-9a2 2 0 0 0-2-2.3zM7 22H4a2 2 0 0 1-2-2v-7a2 2 0 0 1 2-2h3\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t<button\n\t\t\t\tdata-response=\"0\"\n\t\t\t\tdata-post=\"1087\"\n\t\t\t\tdata-post-url=\"https:\/\/www.csharptutorial.net\/csharp-linq\/linq-thenbydescending\/\"\n\t\t\t\tdata-post-title=\"LINQ ThenByDescending\"\n\t\t\t\tclass=\"wth-btn-rounded wth-no-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M10 15v4a3 3 0 0 0 3 3l4-9V2H5.72a2 2 0 0 0-2 1.7l-1.38 9a2 2 0 0 0 2 2.3zm7-13h2.67A2.31 2.31 0 0 1 22 4v7a2.31 2.31 0 0 1-2.33 2H17\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t<div class=\"wth-form hidden\">\n\t\t<div class=\"wth-form-wrapper\">\n\t\t\t<div class=\"wth-title\"><\/div>\n\t\t\t\n\t\t\t<textarea class=\"wth-message\"><\/textarea>\n\n\t\t\t<button class=\"btn btn-primary wth-btn-submit\">Send<\/button>\n\t\t\t<button class=\"btn wth-btn-cancel\">Cancel<\/button>\n\t\t\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this tutorial, you&#8217;ll learn how to use the LINQ ThenByDescending() method to sort a sequence in descending order based on a secondary key.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":919,"menu_order":7,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1087","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1087","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/comments?post=1087"}],"version-history":[{"count":3,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1087\/revisions"}],"predecessor-version":[{"id":2456,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1087\/revisions\/2456"}],"up":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/919"}],"wp:attachment":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/media?parent=1087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}