{"id":407166,"date":"2024-02-20T14:38:39","date_gmt":"2024-02-20T06:38:39","guid":{"rendered":"https:\/\/www.idc.net\/help\/407166\/"},"modified":"2024-02-20T14:38:39","modified_gmt":"2024-02-20T06:38:39","slug":"linq-where%e5%ad%90%e5%8f%a5%e4%bb%8b%e7%bb%8d","status":"publish","type":"post","link":"https:\/\/idc.net\/help\/407166\/","title":{"rendered":"LINQ Where\u5b50\u53e5\u4ecb\u7ecd"},"content":{"rendered":"

\u5728\u5411\u5927\u5bb6\u8be6\u7ec6\u4ecb\u7ecdLINQ Where\u5b50\u53e5\u4e4b\u524d\uff0c\u9996\u5148\u8ba9\u5927\u5bb6\u4e86\u89e3\u4e0bLINQ Where\u5b50\u53e5\u5176\u5b9e\u662f\u7528\u6269\u5c55\u65b9\u6cd5\u6765\u5b9e\u73b0\u7684\uff0c\u7136\u540e\u5168\u9762\u4ecb\u7ecdLINQ Where\u5b50\u53e5\u3002<\/p>\n

LINQ Where\u5b50\u53e5\u5176\u5b9e\u662f\u7528\u6269\u5c55\u65b9\u6cd5\u6765\u5b9e\u73b0\u7684<\/strong><\/p>\n

\u5fae\u8f6f\u66ff\u6211\u4eec\u5b9e\u73b0\u7684 LINQ Where\u5b50\u53e5\u5bf9\u5e94\u7684\u6269\u5c55\u51fd\u6570\u5b9e\u9645\u662f\u5982\u4e0b\u7684\u5b9a\u4e49: <\/p>\n

\n \n \n 
    \n  \n  \n  
  1. namespace System.Linq  <\/span><\/span><\/li>\n  \n  \n  
  2. {  <\/span><\/li>\n  \n  \n  
  3. public delegate TResult Func(TArg0 arg0, TArg1 arg1);  <\/span><\/li>\n  \n  \n  
  4. public static class Enumerable  <\/span><\/li>\n  \n  \n  
  5. {  <\/span><\/li>\n  \n  \n  
  6. public static IEnumerable Where(this IEnumerable source, Func predicate);  <\/span><\/li>\n  \n  \n  
  7. public static IEnumerable Where(this IEnumerable source, Func predicate);  <\/span><\/li>\n  \n  \n  
  8. }  <\/span><\/li>\n  \n  \n  
  9. } <\/span><\/li>\n \n \n <\/ol><\/pre>\n
    \u6211\u4eec\u8fd9\u4e2a\u6269\u5c55\u51fd\u6570\u53c2\u6570\uff1aFunc predicate \u7684\u5b9a\u4e49\u770b\u4e0a\u9762\u4ee3\u7801\u7684\u7eff\u8272delegate \u4ee3\u7801\u3002<\/p>\n
    LINQ Where\u5b50\u53e5\u53c2\u6570\u4e66\u5199\u7684\u662fLambda \u8868\u8fbe\u5f0f<\/strong><\/p>\n
    \n \n \n 
      \n  \n  \n  
    1. (dd, aa) =><\/font><\/strong> dd.Length <<\/font><\/strong> aa<\/font><\/strong> \u5c31\u76f8\u5f53\u4e8e C# 2.0 \u7684\u533f\u540d\u51fd\u6570\u3002 <\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n \n \n <\/ol><\/pre>\n
      LINQ\u4e2d\u6240\u6709\u5173\u952e\u5b57\u6bd4\u5982 Select\uff0cSelectMany\uff0c Count\uff0c All \u7b49\u7b49\u5176\u5b9e\u90fd\u662f\u7528\u6269\u5c55\u65b9\u6cd5\u6765\u5b9e\u73b0\u7684\u3002\u4e0a\u9762\u7684\u7528\u6cd5\u540c\u6837\u4e5f\u9002\u7528\u4e8e\u8fd9\u4e9b\u5173\u952e\u5b57\u5b50\u53e5\u3002\u8fd9\u4e2aLINQ Where\u5b50\u53e5\u4e2dLambda \u8868\u8fbe\u5f0f\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u6570\u7ec4\u7d22\u5f15\uff0c\u6211\u4eec\u53ef\u4ee5\u5728Lambda \u8868\u8fbe\u5f0f\u5185\u90e8\u4f7f\u7528\u6570\u7ec4\u7d22\u5f15\u3002\u6765\u505a\u4e00\u4e9b\u590d\u6742\u7684\u5224\u65ad\u3002\u5177\u6709\u6570\u7ec4\u7d22\u5f15\u7684LINQ\u5173\u952e\u5b57\u9664\u4e86Where\u8fd8\u4ee5\u4e0b\u51e0\u4e2aSelect\uff0cSelectMany\uff0c Count\uff0c All\u3002<\/p>\n
      Select\u5b50\u53e5\u4f7f\u7528\u6570\u7ec4\u7d22\u5f15\u7684\u4f8b\u5b50<\/strong><\/p>\n
      \u4e0b\u9762\u4ee3\u7801\u6709\u4e00\u4e2a\u6574\u6570\u6570\u7ec4\uff0c\u6211\u4eec\u627e\u51fa\u8fd9\u4e2a\u6570\u5b57\u662f\u5426\u8ddf\u4ed6\u5728\u8fd9\u4e2a\u6570\u7ec4\u7684\u4f4d\u7f6e\u4e00\u6837 <\/p>\n
      \n \n \n 
        \n  \n  \n  
      1. public static void LinqDemo01()  <\/span><\/span><\/li>\n  \n  \n  
      2. {  <\/span><\/li>\n  \n  \n  
      3. int[] numbers<\/font> = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };  <\/span><\/span><\/span><\/li>\n  \n  \n  
      4. var numsInPlace<\/font> = numbers<\/font>.Select((num, index) =><\/font><\/strong> 
        new { Num<\/font> = num<\/font>, InPlace<\/font> = (num<\/font> == index) });  <\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n  \n  \n  
      5. Console.WriteLine(\"Number: In-place?\");  <\/span><\/li>\n  \n  \n  
      6. foreach (var n in numsInPlace)  <\/span><\/li>\n  \n  \n  
      7. Console.WriteLine(\"{0}: {1}\", n.Num, n.InPlace);  <\/span><\/li>\n  \n  \n  
      8. } <\/span><\/li>\n \n \n <\/ol><\/pre>\n
        SelectMany \u5b50\u53e5\u4f7f\u7528\u6570\u7ec4\u7d22\u5f15\u7684\u4f8b\u5b50<\/strong><\/p>\n
        \u51e0\u4e2a\u53e5\u5b50\u7ec4\u6210\u7684\u6570\u7ec4\uff0c\u6211\u4eec\u5e0c\u671b\u628a\u8fd9\u51e0\u4e2a\u53e5\u5b50\u62c6\u5206\u6210\u5355\u8bcd\uff0c\u5e76\u663e\u793a\u6bcf\u4e2a\u5355\u8bcd\u5728\u90a3\u4e2a\u53e5\u5b50\u4e2d\u3002\u67e5\u8be2\u8bed\u53e5\u5982\u4e0b\uff1a <\/p>\n
        \n \n \n 
          \n  \n  \n  
        1. public static void Demo01()  <\/span><\/span><\/li>\n  \n  \n  
        2. {  <\/span><\/li>\n  \n  \n  
        3. string[] text<\/font> = { \"Albert was here\",  <\/span><\/span><\/span><\/li>\n  \n  \n  
        4. \"Burke slept late\",  <\/span><\/li>\n  \n  \n  
        5. \"Connor is happy\" };  <\/span><\/li>\n  \n  \n  
        6. var tt<\/font> = text<\/font>.SelectMany((s, index) =><\/font><\/strong> from ss in s.Split(' ') 
          select new { Word<\/font> = ss<\/font>, Index<\/font> = index<\/font> });  <\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n  \n  \n  
        7. foreach (var n in tt)  <\/span><\/li>\n  \n  \n  
        8. Console.WriteLine(\"{0}:{1}\", n.Word,n.Index);  <\/span><\/li>\n  \n  \n  
        9. }  <\/span><\/li>\n \n \n <\/ol><\/pre>\n
          \u3010\u7f16\u8f91\u63a8\u8350\u3011<\/p>\n
            \n
          1. LINQ to SQL Table\u6d45\u8c08<\/font><\/li>\n
          2. Linq\u8bed\u53e5\u95ee\u9898\u7684\u89e3\u51b3\u65b9\u6cd5<\/font><\/li>\n
          3. Ling to sql\u66f4\u65b0\u5b9e\u4f53\u6982\u8ff0<\/font><\/li>\n
          4. Linq\u5b9e\u4f53\u7ee7\u627f\u7b80\u5355\u63cf\u8ff0<\/font><\/li>\n
          5. Linq Library\u6982\u8ff0<\/font><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
            \u5728\u5411\u5927\u5bb6\u8be6\u7ec6\u4ecb\u7ecdLINQ Where\u5b50\u53e5\u4e4b\u524d\uff0c\u9996\u5148\u8ba9\u5927\u5bb6\u4e86\u89e3\u4e0bLINQ Where\u5b50\u53e5\u5176\u5b9e\u662f\u7528\u6269\u5c55\u65b9\u6cd5\u6765\u5b9e\u73b0\u7684 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61],"tags":[],"class_list":["post-407166","post","type-post","status-publish","format-standard","hentry","category-website"],"_links":{"self":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/407166","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/comments?post=407166"}],"version-history":[{"count":0,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/407166\/revisions"}],"wp:attachment":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/media?parent=407166"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/categories?post=407166"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/tags?post=407166"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}