{"id":27163,"date":"2022-12-22T19:07:11","date_gmt":"2022-12-22T13:37:11","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-c-why-does-an-intermediate-array-need-to-be-used-for-defining-a-jagged-array\/"},"modified":"2022-12-22T19:07:11","modified_gmt":"2022-12-22T13:37:11","slug":"solved-c-why-does-an-intermediate-array-need-to-be-used-for-defining-a-jagged-array","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-c-why-does-an-intermediate-array-need-to-be-used-for-defining-a-jagged-array\/","title":{"rendered":"[Solved] C#: Why does an intermediate array need to be used for defining a jagged array?"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-48924769\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"48924769\" data-parentid=\"48916741\" data-score=\"-1\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>The reason is that a jagged array is actually an array of arrays of values.<\/p>\n<p>Since arrays are objects, reference types, it means that if you construct a jagged array with room for 10 arrays, all those array references are initialized to <code>null<\/code>.<\/p>\n<p>In other words:<\/p>\n<pre><code>int[][] a = new int[10][];\na[0][0] = 10;\n<\/code><\/pre>\n<p>throws <code>NullReferenceException<\/code>.<\/p>\n<p>The code can be thought of like this:<\/p>\n<pre><code>int[][] a = new int[10][];\n\nint[] temp = a[0]; \/\/ this works, but temp is now null\ntemp[0] = 10;      \/\/ throws NullReferenceException\n<\/code><\/pre>\n<p>Either you assign a fully populated array into the first slot, or you assign an initialized array without the values, like this:<\/p>\n<pre><code>for (int i = 0; i &lt; 10; i++)\n{\n    serialisableHighScores.scores[i] = new int[3];\n    serialisableHighScores.scores[i][0] = _highScores[i].date;\n    serialisableHighScores.scores[i][1] = _highScores[i].score;\n    serialisableHighScores.scores[i][2] = _highScores[i].questionsAsked;\n}\n<\/code><\/pre>\n<p>Now, that&#8217;s just the explanation of why it crashes on your end. The best option you have available is not to use arrays like this, that is, don&#8217;t use 2-dimensional arrays to keep one list of related values, instead use objects:<\/p>\n<pre><code>public class Score\n{\n    public Score(DateTime date, int score, int questionsAsked)\n    {\n        Date = date;\n        Score = score;\n        QuestionsAsked = questionsAsked;\n    }\n\n    public DateTime Date { get; }\n    public int Score { get; }\n    public int QuestionsAsked { get; }\n}\n<\/code><\/pre>\n<p>Additionally, arrays are good for fixed size things but in general it&#8217;s usually better to use lists:<\/p>\n<pre><code>var serializableHighScores = new List&lt;Score&gt;();\nfor (int i = 0; i &lt; 10; i++)\n{\n    serializableHighScores.Add(new Score(_highScores[i].date, _highScores[i].score, _highScores[i].questionsAsked));\n}\n<\/code><\/pre>\n<p><strong>Though<\/strong> given the name of your variable, if you need to adhere to some badly designed (my opinion) serializing format with arrays of arrays it&#8217;s probably better to just stick with your code.<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">1<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved C#: Why does an intermediate array need to be used for defining a jagged array? <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] The reason is that a jagged array is actually an array of arrays of values. Since arrays are objects, reference types, it means that if you construct a jagged array with room for 10 arrays, all those array references are initialized to null. In other words: int[][] a = new int[10][]; a[0][0] = 10; &#8230; <a title=\"[Solved] C#: Why does an intermediate array need to be used for defining a jagged array?\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-c-why-does-an-intermediate-array-need-to-be-used-for-defining-a-jagged-array\/\" aria-label=\"More on [Solved] C#: Why does an intermediate array need to be used for defining a jagged array?\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[361,324,4209],"class_list":["post-27163","post","type-post","status-publish","format-standard","hentry","category-solved","tag-arrays","tag-c","tag-jagged-arrays"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] C#: Why does an intermediate array need to be used for defining a jagged array? - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-c-why-does-an-intermediate-array-need-to-be-used-for-defining-a-jagged-array\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] C#: Why does an intermediate array need to be used for defining a jagged array? - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] The reason is that a jagged array is actually an array of arrays of values. 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