{"id":757,"date":"2021-09-07T15:56:09","date_gmt":"2021-09-07T07:56:09","guid":{"rendered":"http:\/\/www.wayln.com\/?p=757"},"modified":"2021-09-07T16:56:41","modified_gmt":"2021-09-07T08:56:41","slug":"%e5%bc%82%e6%ad%a5%e7%bc%96%e7%a8%8b","status":"publish","type":"post","link":"https:\/\/www.wayln.com\/?p=757","title":{"rendered":"\u5f02\u6b65\u7f16\u7a0b"},"content":{"rendered":"

\u73b0\u4ee3\u5f02\u6b65.net\u5e94\u7528\u7a0b\u5e8f\u7528\u5230\u4e86\u4e24\u4e2a\u5173\u952e\u5b57\uff0c\u5206\u522b\u662fasync\u548cawait\u3002\u5728\u58f0\u660e\u65b9\u6cd5\u65f6\uff0c\u4f1a\u6dfb\u52a0async\u5173\u952e\u5b57\uff0c\u5b83\u80fd\u53d1\u6325\u4e24\u91cd\u7528\u9014\uff1a\u6fc0\u6d3b\u8be5\u65b9\u6cd5\u4e2d\u7684await\u5173\u952e\u5b57\uff0c\u5e76\u77e5\u4f1a\u7f16\u8bd1\u5668\u4e3a\u8be5\u65b9\u6cd5\u751f\u6210\u4e00\u4e2a\u72b6\u6001\u673a\uff0c\u7c7b\u4f3c\u4e8eyield return\u7684\u5de5\u4f5c\u65b9\u5f0f\u3002\u5982\u679casync\u65b9\u6cd5\u80fd\u53d1\u6325\u4e00\u4e2a\u503c\uff0c\u90a3\u4e48\u8fd9\u4e2a\u503c\u53ef\u80fd\u662fTask<TResult>\u3002\u5982\u679c\u4e0d\u80fd\u8fd4\u56de\u503c\u6216\u8005\u5176\u4ed6\u7c7b\u4f3c\u4e8etask\u7684\u7c7b\u578b\uff0c\u6bd4\u5982ValueTask,\u90a3\u4e48\u4ed6\u4fbf\u4f1a\u8fd4\u56deTask\u3002\u6b64\u5916\uff0c\u82e5async\u65b9\u6cd5\u4ee5\u4e00\u7ec4\u679a\u4e3e\u8fd4\u56de\u4e86\u591a\u4e2a\u503c\uff0c\u4ed6\u4fbf\u4f1a\u8fd4\u56deIAsyncEnumerable<T>\u6216IAsyncEnumerator<T>\u3002\u8fd9\u4e9b\u7c7b\u4f3c\u4e8etask\u7684\u7c7b\u578b\u90fd\u4ee3\u8868future\uff0c\u8fd9\u4e9bfuture\u5219\u4f1a\u5728async\u65b9\u6cd5\u5b8c\u6210\u65f6\u901a\u77e5\u8c03\u7528\u4ee3\u7801\u3002<\/p>\n

\u6ce8\u610f\uff1a\u5207\u6237\u4f7f\u7528async void!\u53ea\u6709\u5728\u7f16\u5199async\u5b9e\u8df5\u5904\u7406\u7a0b\u5e8f\u65f6\uff0c\u624d\u9700\u8981\u4f7f\u7528async\u65b9\u6cd5\u6765\u8fd4\u56devoid.\u65e0\u8fd4\u56de\u503c\u7684\u5e38\u89c4async\u65b9\u6cd5\u5e94\u5f53\u8fd4\u56deTask,\u800c\u975evoid<\/strong><\/p>\n

async Task DoSomethingAsync()\n{\n    int value=13;\n    \/\/\u5f02\u6b65\u7b49\u5f851\u79d2\n    await Task.Delay(TimeSpan.FromSeconds(1));\n    value*=2;\n    \/\/\u5f02\u6b65\u7b49\u5f85\u4e24\u79d2\n    await Task.Delay(TimeSpan.FromSeconds(1));\n    Trace.WriteLine(value);\n}\n<\/code><\/pre>\n
\u4e0e\u5176\u4ed6\u65b9\u6cd5\u4e00\u6837\uff0casync\u65b9\u6cd5\u4e00\u5f00\u59cb\u540c\u6b65\u6267\u884c\u3002\u5728async\u65b9\u6cd5\u4e2d\uff0cawait\u5173\u952e\u5b57\u4f1a\u5bf9\u5176\u5b9e\u9645\u53c2\u6570\u6267\u884c\u5f02\u6b65\u7b49\u5f85\u3002\u5f02\u6b65\u7b49\u5f85\u4f1a\u68c0\u67e5\u64cd\u4f5c\u662f\u5426\u5df2\u7ecf\u5b8c\u6210\u3002\u82e5\u5df2\u5b8c\u6210\uff0c\u4ed6\u4fbf\u4f1a\u7ee7\u7eed\u540c\u6b65\u6267\u884c\u3002\u5426\u5219\uff0c\u4ed6\u4f1a\u8ba9async\u65b9\u6cd5\u6682\u505c\u5e76\u8fd4\u56de\u4e00\u4e2a\u4e0d\u5b8c\u6574\u7684\u4efb\u52a1\u3002\u5f53\u968f\u540e\u64cd\u4f5c\u5b8c\u6210\u65f6\uff0casync\u65b9\u6cd5\u4f1a\u6062\u590d\u6267\u884c\u3002
\n\u53ef\u4ee5\u628aasync\u65b9\u6cd5\u5f53\u505a\u82e5\u5e72\u4e2a\u7531await\u8bed\u53e5\u5206\u5272\u800c\u6210\u7684\u540c\u6b65\u90e8\u5206\u3002\u54ea\u4e00\u4e2a\u7ebf\u7a0b\u8c03\u7528\u65b9\u6cd5\uff0c\u7b2c\u4e00\u4e2a\u540c\u6b65\u90e8\u5206\u5c31\u5728\u54ea\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u6267\u884c\u3002\u4f46\u662f\u5176\u4ed6\u7684\u540c\u6b65\u90e8\u5206\u5728\u54ea\u513f\u6267\u884c\u5462\uff1f\u7b54\u6848\u6709\u4e00\u70b9\u590d\u6742\u3002
\n\u4ee5\u6700\u5e38\u89c1\u7684\u573a\u666f\u4e3a\u4f8b\uff0c\u5f53\u7b49\u5f85\u67d0\u4e2a\u4efb\u52a1\u65f6\uff0c\u5982\u679cawait\u51b3\u5b9a\u6682\u505c\u65b9\u6cd5\uff0c\u90a3\u4e48\u8fd9\u65f6\u4f1a\u6355\u6349\u5230\u4e00\u4e2a\u4e0a\u4e0b\u6587(context)\u3002\u5982\u679c\u4e0d\u4e3anull\uff0c\u5b83\u4fbf\u662f\u5f53\u524d\u7684synchronizationContext\u3002\u4f46\u5982\u679c\u662fnull,\u4e0a\u4e0b\u6587\u5219\u4e3a\u5f53\u524d\u7684TaskScheduler\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u65b9\u6cd5\u90fd\u4f1a\u5728\u88ab\u6355\u6349\u7684\u4e0a\u4e0b\u6587\u4e2d\u7ee7\u7eed\u6267\u884c\u3002\u901a\u5e38\uff0c\u5982\u679c\u5f53\u524d\u73af\u5883\u662fUI\u7ebf\u7a0b\uff0c\u90a3\u4e48\u8fd9\u4e2a\u4e0a\u4e0b\u6587\u662fUI\u4e0a\u4e0b\u6587\uff1b\u5982\u679c\u662f\u5176\u4ed6\u73af\u5883\uff0c\u5219\u5f80\u5f80\u4f1a\u4f7f\u7ebf\u7a0b\u6c60\u4e0a\u4e0b\u6587\u3002
\n\u5728\u4e0a\u9762\u4ee3\u7801\u4e2d\uff0c\u6240\u6709\u7684\u540c\u6b65\u90e8\u5206\u90fd\u4f1a\u8bd5\u56fe\u5728\u539f\u5148\u7684\u4e0a\u9650\u4e3a\u4e2d\u7ee7\u7eed\u8fd0\u884c\u3002\u5982\u679c\u4eceUI\u7ebf\u7a0b\u4e2d\u8c03\u7528DoSomethingAsync\uff0c\u5b83\u7684\u6bcf\u4e00\u4e2a\u540c\u6b65\u90e8\u5206\u90fd\u5c06\u5728\u8be5UI\u7ebf\u7a0b\u4e2d\u8fd0\u884c\u3002\u5982\u679c\u4ece\u7ebf\u7a0b\u6c60\u7684\u67d0\u4e2a\u7ebf\u7a0b\u4e2d\u8c03\u7528\u5b83\uff0c\u90a3\u4e48\u8fd9\u4e9b\u540c\u6b65\u90e8\u5206\u5c06\u5728\u7ebf\u7a0b\u6c60\u7684\u4efb\u610f\u7ebf\u7a0b\u4e2d\u8fd0\u884c\u3002
\n\u901a\u8fc7\u5f02\u6b65\u7b49\u5f85ConfigureAwait\u6269\u5c55\u65b9\u6cd5\u7684\u7ed3\u679c\uff0c\u5e76\u5c06false\u4f5c\u4e3acontinueOnCapturedContext\u53c2\u6570\u7684\u503c\u4f20\u5165\uff0c\u53ef\u4ee5\u89c4\u907f\u8fd9\u79cd\u9ed8\u8ba4\u7684\u884c\u4e3a\u3002\u4e0b\u9762\u7684\u4ee3\u7801\u4ece\u8c03\u7528\u7ebf\u7a0b\u5f00\u59cb\uff0c\u5f53\u88abawait\u6682\u505c\u540e\uff0c\u5b83\u4f1a\u5728\u7ebf\u7a0b\u6c60\u4e2d\u7ee7\u7eed\u8fd0\u884c\u3002<\/p>\n
async Task DoSomethingAsync()\n{\n    int value=13;\n    \/\/\u5f02\u6b65\u7b49\u5f851\u79d2\n    await Task.Delay(TimeSpan.FromSeconds(1)).ConfigureAwait(false);\n    value*=2;\n    \/\/\u5f02\u6b65\u7b49\u5f85\u4e24\u79d2\n    await Task.Delay(TimeSpan.FromSeconds(1)).ConfigureAwait(false);\n    Trace.WriteLine(value);\n}\n<\/code><\/pre>\n
\u59cb\u7ec8\u5728\u6838\u5fc3”\u5e93”\u65b9\u6cd5\u4e2d\u8c03\u7528ConfigureAwait\uff0c\u5e76\u4e14\uff0c\u4ec5\u5f53\u5728\u5916\u90e8\u201c\u7528\u6237\u754c\u9762\u201d\u65b9\u6cd5\u4e2d\u9700\u8981\u5b83\u65f6\u624d\u6062\u590d\u4e0a\u4e0b\u6587\uff0c\u8fd9\u662f\u5f88\u597d\u7684\u505a\u6cd5<\/strong><\/p>\n
await\u5173\u952e\u5b57\u5e76\u4e0d\u4ec5\u9650\u4e8e\u5904\u7406\u4efb\u52a1\uff0c\u5b83\u4e5f\u53ef\u4ee5\u5904\u7406\u4efb\u4f55\u7b26\u5408\u7279\u5b9a\u683c\u5f0f\u7684\u53ef\u7b49\u5f85\u5bf9\u8c61\u3002\u4f46\u662f\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0cawait\u5904\u7406\u7684\u662fTask\u6216Task<TResult>\u3002<\/p>\n
\u53ef\u4ee5\u901a\u8fc7\u4e24\u79cd\u65b9\u6cd5\u6765\u521b\u5efaTask\u5b9e\u4f8b\u3002
\n1. \u67d0\u4e9b\u4efb\u52a1\u4ee3\u8868\u7684\u662fCPU\u9700\u8981\u6267\u884c\u7684\u5b9e\u9645\u4ee3\u7801\uff0c\u8fd9\u662f\u8981\u8c03\u7528Task.Run\u6765\u521b\u5efa\u8fd9\u4e9b\u8fd0\u7b97\u578b\u7684\u4efb\u52a1
\n2. \u8981\u5728\u67d0\u4e2a\u7279\u5b9a\u7684\u8c03\u5ea6\u5668\u4e0a\u8fd0\u884c\u8fd9\u4e9b\u4efb\u52a1\u3002\u9700\u8981\u8c03\u7528Task.Factory.StartNew
\n3. \u521b\u5efa\u57fa\u4e8e\u5b9e\u8df5\u7684\u4efb\u52a1\u5e94\u5f53\u91c7\u7528TaskCompletionSource<TResult>(\u6216\u8005\u5b83\u7684\u67d0\u79cd\u5feb\u6377\u65b9\u5f0f)\u3002\u5927\u591a\u6570I\/O\u4efb\u52a1\u91c7\u7528\u4e86TaskCompletionSource<TResult><\/p>\n
\u5f02\u5e38\u5904\u7406<\/h1>\n
\u5728\u4e0b\u9762\u4ee3\u7801\u4e2d\uff0cPossibleExceptionAsync\u53ef\u80fd\u629b\u51faNotSupportedException\u5f02\u5e38\uff0c\u4f46TrySomethingAsync\u4f1a\u672c\u80fd\u5730\u6355\u6349\u5f02\u5e38\u3002\u5bf9\u4e8e\u88ab\u6355\u6349\u7684\u5f02\u5e38\uff0c\u5176\u6808\u8ffd\u8e2a\u4f1a\u59a5\u5584\u5730\u4fdd\u7559\u4e0b\u6765\uff0c\u800c\u4e0d\u4f1a\u88ab\u8ba4\u4e3a\u5730\u5305\u88c5\u5230TargetInvocationException\u6216AggregateException\u4e2d\uff1a<\/p>\n
async Task TrySomethingAsync()\n{\n    try\n    {\n        await PossibleExceptionAsync();\n    }\n    catch(NotSupportedException ex)\n    {\n        LogException(ex);\n        throw;\n    }\n}\n<\/code><\/pre>\n
\u5f53async\u65b9\u6cd5\u629b\u51fa\u6216\u4f20\u64ad\u5f02\u5e38\u65f6\uff0c\u8be5\u5f02\u5e38\u88ab\u653e\u5165\u5b83\u8fd4\u56de\u7684Task\u4e2d\uff0c\u8be5Task\u5c31\u6b64\u5b8c\u6210\u3002\u5f53\u8be5Task\u51fa\u5728\u5f02\u6b65\u7b49\u5f85\u9636\u6bb5\u65f6\uff0cawait\u8fd0\u7b97\u7b26\u4f1a\u63a5\u6536\u5230\u8be5\u5f02\u5e38\u5e76\u5c06\u5176\u518d\u6b21\u629b\u51fa\uff0c\u671f\u95f4\uff0c\u5b83\u7684\u539f\u59cb\u6808\u8ffd\u8e2a\u4f1a\u5f97\u4ee5\u4fdd\u7559\u3002\u56e0\u6b64\uff0c\u5982\u679cPossibleExceptionAsync\u662f\u4e00\u79cdasync\u65b9\u6cd5\uff0c\u90a3\u4e48\u4ee5\u4e0b\u4ee3\u7801\u5c31\u4f1a\u5982\u9884\u671f\u90a3\u6837\u5de5\u4f5c\uff1a<\/p>\n
async Task TrySomethingAsync()\n{\n    \/\/\u5f02\u5e38\u4f1a\u5728Task\u51fa\u73b0\u65f6\u7ec8\u6b62\uff0c\u5e76\u4e0d\u4f1a\u88ab\u76f4\u63a5\u629b\u51fa\n    Task task=PossibleExceptionAsync();\n    try\n    {\n        \/\/Task\u7684\u5f02\u5e38\u4f1a\u5728\u6b64\u5904\u53d1\u751f\n        await task\uff1b\n    }\n    catch(NotSupportedException ex)\n    {\n        LogException(ex);\n        throw;\n    }\n}\n<\/code><\/pre>\n
\u5bf9\u4e8easync\u65b9\u6cd5\uff0c\u8fd8\u6709\u4e00\u6761\u91cd\u8981\u7684\u51c6\u5219\uff1a\u4e00\u65e6\u5f00\u59cb\u4f7f\u7528async,\u6700\u597d\u4efb\u7531\u5b83\u5728\u4ee3\u7801\u4e2d\u8fd0\u884c\u3002\u5982\u679c\u8c03\u7528async\u65b9\u6cd5\uff0c\u7ec8\u7a76\u8981\u7b49\u5f85\u5b83\u8fd4\u56de\u7684\u4efb\u52a1\u3002\u5c3d\u91cf\u4e0d\u8981\u8c03\u7528Task.Wait\u3001Task<TResult>.Result\u6216GetAwaiter().GetResult()\uff0c\u5426\u5219\u53ef\u80fd\u5f15\u53d1\u6b7b\u9501\uff1a<\/p>\n
async Task WaitAsync()\n{\n    \/\/\u8be5await\u4f1a\u6355\u83b7\u5f53\u524d\u7684\u4e0a\u4e0b\u6587\n    await Task.Delay(TimeSpan.FromSeconds(1));\n    \/\/\u8fd8\u4f1a\u5c1d\u8bd5\u5728\u8be5\u4e0a\u4e0b\u6587\u4e2d\u7ee7\u7eed\u6267\u884c\u8fd9\u4e2a\u65b9\u6cd5\n}\nvoid Deadlock()\n{\n    \/\/\u5f00\u59cb\u5ef6\u8fdf\n    Task task=WaitAsync();\n    \/\/\u540c\u6b65\u5730\u963b\u585e\u5e76\u7b49\u5f85async\u65b9\u6cd5\u5b8c\u6210\uff1b\n    task.Wait();\n}\n<\/code><\/pre>\n
\u5982\u679c\u5728UI\u4e0a\u4e0b\u6587\u6216ASP.NET Classic\u4e0a\u4e0b\u6587\u4e2d\u8c03\u7528\u6b64\u4f8b\u4e2d\u7684\u4ee3\u7801\uff0c\u4fbf\u4f1a\u5f15\u53d1\u6b7b\u9501\uff0c\u56e0\u4e3a\u8fd9\u4e24\u79cd\u4e0a\u4e0b\u6587\u4e00\u6b21\u90fd\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u3002Deadlock\u4f1a\u8c03\u7528WaitAsync\uff0c\u5f15\u53d1\u5ef6\u8fdf\u3002\u968f\u540e\uff0cDeadlock\u4f1a\u540c\u6b65\u7b49\u5f85\u65b9\u6cd5\u5b8c\u6210\uff0c\u5e76\u963b\u585e\u4e0a\u4e0b\u6587\u7ebf\u7a0b\u3002\u5f53\u5ef6\u8fdf\u7ed3\u675f\u540e\uff0cawait\u4f1a\u5c1d\u8bd5\u5728\u88ab\u6355\u83b7\u7684\u4e0a\u4e0b\u6587\u4e2d\u6062\u590dWaitAsync,\u4f46\u65e0\u6cd5\u6062\u590d\uff0c\u56e0\u4e3a\u5728\u4e0a\u4e0b\u6587\u4e2d\u5df2\u6709\u4e00\u4e2a\u53d7\u963b\u585e\u7684\u7ebf\u7a0b\uff0c\u4e14\u8be5\u4e0a\u9650\u4e3a\u4e00\u6b21\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u3002
\nwait\u7ebf\u7a0b\u9501\uff1a\u4e3b\u6267\u884c\u7ebf\u7a0b\u8c03\u7528\u5b50\u7ebf\u7a0b\u540e\u6302\u8d77\u7b49\u5f85\u5b50\u7ebf\u7a0b\u7ed3\u679c\uff0c\u5b50\u7ebf\u7a0b\u53c8\u9700\u8981\u5207\u6362\u5230\u4e3b\u7ebf\u7a0b\u6216\u8005\u7b49\u5f85\u4e3b\u7ebf\u7a0b\u8fd4\u56de\uff0c\u4ece\u800c\u5bfc\u81f4\u4e24\u4e2a\u7ebf\u7a0b\u5747\u5904\u5728\u963b\u585e\u72b6\u6001\uff08\u6b7b\u9501\uff09
\n\u6709\u4e24\u79cd\u65b9\u6cd5\u80fd\u9884\u9632\u6b7b\u9501\uff1a
\n1. \u5728WaitAsync\u4e2d\u4f7f\u7528ConfigureAwait(false)(\u8fd9\u6837\u4f1a\u8ba9await\u5ffd\u89c6\u5b83\u7684\u4e0a\u4e0b\u6587)
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