{"id":8921,"date":"2014-06-06T11:07:07","date_gmt":"2014-06-06T03:07:07","guid":{"rendered":"http:\/\/bohu.net\/blog\/?p=8921"},"modified":"2014-06-06T11:07:07","modified_gmt":"2014-06-06T03:07:07","slug":"c%e4%b8%ad%e7%9a%84%e5%8f%b7%e5%8f%8a%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/www.bohu.net\/blog\/8921\/","title":{"rendered":"C#\u4e2d\u7684&#8217;?\u53f7&#8217;\u53ca\u7528\u6cd5"},"content":{"rendered":"<p>1.\u00a0\u53ef\u7a7a\u7c7b\u578b\u4fee\u9970\u7b26(\uff1f)\uff1a<\/p>\n<blockquote>\n<pre>\u3000\u3000\u5f15\u7528\u7c7b\u578b\u53ef\u4ee5\u4f7f\u7528\u7a7a\u5f15\u7528\u8868\u793a\u4e00\u4e2a\u4e0d\u5b58\u5728\u7684\u503c,\u800c\u503c\u7c7b\u578b\u901a\u5e38\u4e0d\u80fd\u8868\u793a\u4e3a\u7a7a\u3002\n\u3000\u3000\u4f8b\u5982:\n    string str=null;\u662f\u6b63\u786e\u7684\u3002\n    int i=null\uff1b\u7f16\u8bd1\u5668\u5c06\u62a5\u9519\u3002\n    \u4e3a\u4e86\u4f7f\u503c\u7c7b\u578b\u4e5f\u53ef\u4e3a\u7a7a,\u53ef\u7a7a\u7c7b\u578b\u51fa\u73b0\u4e86,\u53ef\u7a7a\u7c7b\u578b\u4f7f\u7528\u53ef\u7a7a\u7c7b\u578b\u4fee\u9970\u7b26\uff1f\u6765\u8868\u793a,\u8868\u73b0\u5f62\u5f0f\u4e3aT?\u3002\n\u3000\u3000\u4f8b\uff1aint?\u8868\u793a\u662f\u53ef\u7a7a\u7684\u6574\u5f62,DateTime?\u8868\u793a\u4e3a\u53ef\u7a7a\u7684\u65f6\u95f4\u3002\n\u3000\u3000T?\u5176\u5b9e\u662fSystem.Nullable&lt;T&gt;\uff08\u6cdb\u578b\u7ed3\u6784\uff09\u7684\u7f29\u5199\u5f62\u5f0f,\u4e5f\u5c31\u610f\u5473\u7740\u5f53\u4f60\u7528\u5230T\uff1f\u65f6\u7f16\u8bd1\u5668\u5728\u7f16\u8bd1\u65f6\u4f1a\u628aT\uff1f\u7f16\u8bd1\u6210System.Nullable&lt;T&gt;\u7684\u5f62\u5f0f,\n\u3000\u3000\u4f8b\u5982\uff1aint?,\u7f16\u8bd1\u540e\u4fbf\u662fSystem.Nullable&lt;int&gt;\u7684\u5f62\u5f0f\u3002<\/pre>\n<\/blockquote>\n<p>2.\u00a0\u4e09\u5143\uff08\u8fd0\u7b97\u7b26\uff09\u8868\u8fbe\u5f0f(\uff1f:)\uff1a<\/p>\n<blockquote>\n<pre>\u8bed\u6cd5\u4e3a\uff1a\u6761\u4ef6\u8868\u8fbe\u5f0f\uff1f\u8868\u8fbe\u5f0f1\uff1a\u8868\u8fbe\u5f0f2\uff1b\n\u8be5\u64cd\u4f5c\u9996\u5148\u6c42\u51fa\u6761\u4ef6\u8868\u8fbe\u5f0f\u7684\u503c(bool\u7c7b\u578b),\u4e3atrue\u65f6\u8c03\u7528\u8868\u8fbe\u5f0f1,\u4e3aflase\u65f6\u8c03\u7528\u8868\u8fbe\u5f0f2\u3002\n\u5176\u903b\u8f91\u4e3a\uff1a\"\u5982\u679c\u4e3a\u771f\u6267\u884c\u7b2c\u4e00\u4e2a,\u5426\u5219\u6267\u884c\u7b2c\u4e8c\u4e2a\u3002\"\n\n \u4f8b\uff1a\n test ? expression1 : expression2\n test \u4efb\u4f55 Boolean \u8868\u8fbe\u5f0f\u3002\n expression1 test \u4e3a true \u65f6\u8fd4\u56de\u7684\u8868\u8fbe\u5f0f\u3002\u53ef\u80fd\u662f\u9017\u70b9\u8868\u8fbe\u5f0f\u3002\n expression2 test \u4e3a false \u65f6\u8fd4\u56de\u7684\u8868\u8fbe\u5f0f\u3002\u53ef\u80fd\u662f\u9017\u70b9\u8868\u8fbe\u5f0f\u3002\n\n \u4f8b\u5982\uff1a\n string prm1=\"4\"; string prm2=\"5\";\n string prm3 = prm1==prm2?\"yes\":\"no\" \/\/ \u6b64\u65f6prm3\u503c\u4e3a\"no\".<\/pre>\n<\/blockquote>\n<p>3.\u00a0\u7a7a\u5408\u5e76\u8fd0\u7b97\u7b26(\uff1f\uff1f)\uff1a<\/p>\n<blockquote>\n<pre>\u7a7a\u5408\u5e76\u8fd0\u7b97\u7b26 (null coalescing operator) ??\n\u3000\u3000\u7528\u4e8e\u5b9a\u4e49\u53ef\u7a7a\u7c7b\u578b\u548c\u5f15\u7528\u7c7b\u578b\u7684\u9ed8\u8ba4\u503c\u3002\u5982\u679c\u6b64\u8fd0\u7b97\u7b26\u7684\u5de6\u64cd\u4f5c\u6570\u4e0d\u4e3a null\uff0c\u5219\u6b64\u8fd0\u7b97\u7b26\u5c06\u8fd4\u56de\u5de6\u64cd\u4f5c\u6570\uff1b\u5426\u5219\u8fd4\u56de\u53f3\u64cd\u4f5c\u6570\u3002\n\u3000\u3000\u4f8b\uff1aa??b \u5982\u679c a \u4e3a\u975e\u7a7a\uff0c\u5219 a ?? b \u7684\u7ed3\u679c\u4e3a a\uff1b\u5426\u5219\u7ed3\u679c\u4e3a b \u3002\n\n\u7a7a\u5408\u5e76\u8fd0\u7b97\u7b26\u4e3a\u53f3\u7ed3\u5408\u8fd0\u7b97\u7b26\uff0c\u5373\u64cd\u4f5c\u65f6\u4ece\u53f3\u5411\u5de6\u8fdb\u884c\u7ec4\u5408\u7684\u3002\n\u3000\u3000\u4f8b\uff1a\u201ca??b??c\u201d\u7684\u5f62\u5f0f\u6309\u201ca??(b??c)\u201d\u8ba1\u7b97\u3002<\/pre>\n<p>&nbsp;<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>1.\u00a0\u53ef\u7a7a\u7c7b\u578b\u4fee\u9970\u7b26(\uff1f)\uff1a \u3000\u3000\u5f15\u7528\u7c7b\u578b\u53ef\u4ee5\u4f7f\u7528\u7a7a\u5f15\u7528\u8868\u793a\u4e00\u4e2a\u4e0d\u5b58\u5728\u7684\u503c,\u800c\u503c\u7c7b\u578b\u901a\u5e38\u4e0d\u80fd\u8868\u793a\u4e3a\u7a7a\u3002 \u3000\u3000\u4f8b &hellip; <a href=\"https:\/\/www.bohu.net\/blog\/8921\/\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201cC#\u4e2d\u7684&#8217;?\u53f7&#8217;\u53ca\u7528\u6cd5\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,4,26],"tags":[45,46,98,272,446,580,618],"class_list":["post-8921","post","type-post","status-publish","format-standard","hentry","category-net","category-c-net","category-26","tag-45","tag-46","tag-c","tag-null-coalescing-operator","tag-446","tag-580","tag-618"],"_links":{"self":[{"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/posts\/8921","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/comments?post=8921"}],"version-history":[{"count":0,"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/posts\/8921\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/media?parent=8921"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/categories?post=8921"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bohu.net\/blog\/wp-json\/wp\/v2\/tags?post=8921"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}