c# - 元组 lambda 语法突然在 C# 中不起作用

Question

我正在使用.NET Framework 4.7，我已经实现了几个这样的语法

Task<(bool isSuccess, string message)> DownloadFileResource()

它已经通过获得结果而起作用var

var downloadResult = await BlobUtils.DownloadFileResource()

但是今天当我打开visual studio时，我所有的var转换都dynamic作为IDE的建议输入，不再是a (bool isSuccess, string message)，并且在运行时抛出错误

 Microsoft.CSharp.RuntimeBinder.RuntimeBinderException:
 'System.ValueTuple<bool,string>' does not contain a definition for > 'isSuccess'
    at CallSite.Target(Closure , CallSite , Object )
    at System.Dynamic.UpdateDelegates.UpdateAndExecute1[T0,TRet](CallSite  site, T0 arg0)
    at DataUnitCrawler.MainFormV3.<DownloadFileResource>d__10.MoveNext() in D:\Gannha\GannhaDesktopApp\DataUnitCrawler\MainFormV3.cs:line 97
 --- End of stack trace from previous location where exception was thrown ---
 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
 at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() 
 at DataUnitCrawler.MainFormV3.<<-ctor>b__9_1>d.MoveNext() in D:\Gannha\GannhaDesktopApp\DataUnitCrawler\MainFormV3.cs:line 86
 --- End of stack trace from previous location where exception was thrown ---
 at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<>c.<ThrowAsync>b__6_0(Object state)


************** Loaded Assemblies ************** mscorlib
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
---------------------------------------- DataUnitCrawler
    Assembly Version: 1.0.0.0
    Win32 Version: 1.0.0.0
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/DataUnitCrawler.exe
---------------------------------------- System.Windows.Forms
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
---------------------------------------- System
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4001.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
---------------------------------------- System.Drawing
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0 built by: NET48REL1
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
---------------------------------------- System.Data
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_32/System.Data/v4.0_4.0.0.0__b77a5c561934e089/System.Data.dll
---------------------------------------- System.Core
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
---------------------------------------- System.Xml
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0 built by: NET48REL1
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll
---------------------------------------- DataUtility
    Assembly Version: 1.0.0.0
    Win32 Version: 1.0.0.0
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/DataUtility.DLL
---------------------------------------- Microsoft.WindowsAzure.Storage
    Assembly Version: 9.3.2.0
    Win32 Version: 9.3.2.0
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/Microsoft.WindowsAzure.Storage.DLL
---------------------------------------- Microsoft.CSharp
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/Microsoft.CSharp/v4.0_4.0.0.0__b03f5f7f11d50a3a/Microsoft.CSharp.dll
---------------------------------------- System.Configuration
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0 built by: NET48REL1
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
---------------------------------------- Newtonsoft.Json
    Assembly Version: 12.0.0.0
    Win32 Version: 12.0.1.22727
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/Newtonsoft.Json.DLL
---------------------------------------- System.Numerics
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0 built by: NET48REL1
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Numerics/v4.0_4.0.0.0__b77a5c561934e089/System.Numerics.dll
---------------------------------------- System.Runtime.Serialization
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Runtime.Serialization/v4.0_4.0.0.0__b77a5c561934e089/System.Runtime.Serialization.dll
---------------------------------------- System.Dynamic
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.3752.0
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Dynamic/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Dynamic.dll
---------------------------------------- Anonymously Hosted DynamicMethods Assembly
    Assembly Version: 0.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_32/mscorlib/v4.0_4.0.0.0__b77a5c561934e089/mscorlib.dll
---------------------------------------- NLog
    Assembly Version: 4.0.0.0
    Win32 Version: 4.5.11.8645
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/NLog.DLL
---------------------------------------- NLog.Windows.Forms
    Assembly Version: 4.0.0.0
    Win32 Version: 4.2.3.167
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/NLog.Windows.Forms.DLL
---------------------------------------- System.ServiceModel
    Assembly Version: 4.0.0.0
    Win32 Version: 4.8.4121.0 built by: NET48REL1LAST_C
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.ServiceModel/v4.0_4.0.0.0__b77a5c561934e089/System.ServiceModel.dll
---------------------------------------- Microsoft.Azure.Storage.Blob
    Assembly Version: 11.1.1.0
    Win32 Version: 11.1.1
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/Microsoft.Azure.Storage.Blob.DLL
---------------------------------------- Microsoft.Azure.Storage.Common
    Assembly Version: 11.1.1.0
    Win32 Version: 11.1.1.0
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/Microsoft.Azure.Storage.Common.DLL
---------------------------------------- System.Net.Http
    Assembly Version: 4.2.0.0
    Win32 Version: 4.6.26011.01
    CodeBase: file:///D:/Gannha/GannhaDesktopApp/DataUnitCrawler/bin/Debug/System.Net.Http.DLL
----------------------------------------

************** JIT Debugging ************** To enable just-in-time (JIT) debugging, the .config file for this application or computer
(machine.config) must have the jitDebugging value set in the
system.windows.forms section. The application must also be compiled
with debugging enabled.

For example:

<configuration>
    <system.windows.forms jitDebugging="true" /> </configuration>

When JIT debugging is enabled, any unhandled exception will be sent to
the JIT debugger registered on the computer rather than be handled by
this dialog box.

当我设置断点时，它们会显示item1,item2而不是isSuccess,message

我通过明确声明进行了测试，它有效吗？这很困惑

简而言之，问题是我已经使用ValueTuple函数(bool isSuccess, string message)类型语法很长时间了，并且通常使用var. 知道该var类型直到今天它带有type和dynamicoff all属性。isSuccessmessage

更短：我的预期：（我在 .Net Core 2.1 中测试过）

IDE 的作用：

如何解决？这是一个错误？

score 2 · Accepted Answer

isSuccess不是一个字段ValueTuple<bool, string>- 它只是编译器附加的一个名称ValueTuple<bool, string>.Item，因此dynamic无法使用它。

我非常怀疑 IDE 建议该建议dynamic的 IDE 代码是什么？

更新

我正在使用 Microsoft Visual Studio Enterprise 2019 版本 16.4.6，它非常清楚那result2是dynamic，那result2.message是dynamic。

dynamic意味着它将在运行时解析 whereresult2将是 a ValueTuple<bool, string>，它没有message属性或字段。

这是一个错误，但您的代码中存在错误，请注意 IDE。

您可以在sharplab.io中查看您的代码。在右侧，您将看到翻译后的代码，将源代码悬停在左侧（在左侧），您将看到解释代码的工具提示。

score 1 · Accepted Answer

我花了将近 10 个小时将 4.7 升级到 4.7.2，安装了最新的 16.4.6 VS，更新了所有依赖项，但仍然出现错误。

所以我最终通过将所有更改var result为显式来结束它(bool isMessage, string message) result。很遗憾，它无法获得 lambda 元组的全部真正力量。

- - - 更新

我知道错误是什么，因为我的参数被传递，因为dynamic即使 IDE 知道它是一个字符串，但var不能。

public static Task<(bool isSuccess, string message)> TestTuple(string param) => Task.FromResult((true, param));
public static dynamic GetItWillBeBug() => "abc";
public static string GetItWontBeBug() => "abc";

我的调用方式

static async Task Main(string[] args)
{
    var result1 = await TestTuple(GetItWontBeBug());
    var result2 = await TestTuple(GetItWillBeBug());

    Console.WriteLine("It won't be crashed");
    Console.WriteLine(result1.message);

    Console.WriteLine("It will be crashed");
    Console.WriteLine(result2.message);
}

这肯定是 IDE 的一个错误，希望有人可以向开发人员提出这个问题。

c# - 元组 lambda 语法突然在 C# 中不起作用

2 回答 2

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