Tuple lambda syntax suddenly not working in C#

Question

I'm using .NET Framework 4.7, I have implemented several of syntax like this

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

And it already worked by getting there result with var

var downloadResult = await BlobUtils.DownloadFileResource()

But today when I open visual studio, all my var transform to dynamic type as a suggestion from IDE, not a (bool isSuccess, string message) anymore, and throw error when running it

 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.

When I put a breakpoint, they show item1, item2 instead of isSuccess, message

I tested by declaring explicitly and it worked? That's very confused

For short, the problem is I have used ValueTuple of (bool isSuccess, string message) function type syntax for a long time and got value normally with var. The var knew expected the type until today it comes with dynamic type and off all isSuccess, message attributes.

Shorter: what I expected: (I tested in .Net Core 2.1)

What IDE does:

How to solve it? It's a bug?

I don't see how `await await BlobUtils.DownloadFileResource()` could ever have worked in your case: you return a `Task` where `T` is not awaitable, so this should always have been a syntax error — canton7, Mar 11 '20 at 09:12
@canton7 Judging from the screenshots, the dupe `await` seems to be a typo in the question text. — Fildor, Mar 11 '20 at 09:16
Yes `await` dupe is a typo. Basically the code have been run successfully for long time. No problem until today. — Tấn Nguyên, Mar 11 '20 at 09:22
Are you sure you didn't accidentally open the project in an older version of Visual Studio? — canton7, Mar 11 '20 at 09:36
I'm using 16.4.5 for a while. I'm updating to lasted 16.4.6 now, hope all good :( — Tấn Nguyên, Mar 11 '20 at 09:42

Paulo Morgado · Accepted Answer · 2020-03-12T16:51:12.753

2

isSuccess is not a field of ValueTuple<bool, string>- It's just a name the compiler attahces to ValueTuple<bool, string>.Item and, thus, dynamic can't get to it.

I very much doubt the IDE suggested dynamic what was the IDE code of that suggestion?

Update

I'm using Microsoft Visual Studio Enterprise 2019 Version 16.4.6 and it knows pretty well that result2 is dynamic and that result2.message is dynamic.

dynamic means that it will be resolved at run-time where result2 will be a ValueTuple<bool, string>, which doesn't have a message property or field.

It's a bug, but a bug in your code, note the IDE.

You can look at your code in sharplab.io. On the right side you'll see the translated code and hovering the source code (on the left), you'll see tooltips explaining the code.

edited Mar 12 '20 at 16:51

answered Mar 11 '20 at 13:47

Paulo Morgado

14,111
3
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There `dynamic` suggestion https://i.stack.imgur.com/zZkht.png , and I tested in .Net Core 2.1 it show like this https://i.stack.imgur.com/tdvwk.png – Tấn Nguyên Mar 12 '20 at 03:08
I tried update to 16.4.6, updated to .Net Framework 4.7.2, reinstalled all nugets and still got error. – Tấn Nguyên Mar 12 '20 at 03:11
That's not a **dynamic** suggestion. No matter what you install or uninstall, it won't work because it was never meant to work. – Paulo Morgado Mar 12 '20 at 08:04
Yes I may use another term instead of suggestion meaning. Because it comes with ridiculous significant and what I could describe is that. This topic get the same error with me, but he used VS2019 and worked well. https://stackoverflow.com/questions/41444981/c-sharp-7-valuetuple-compile-error – Tấn Nguyên Mar 12 '20 at 08:19
Oops I knew the bug is https://stackoverflow.com/a/60648530/3789481 – Tấn Nguyên Mar 12 '20 at 08:47
+1, thank you for explanation, I'm getting familiar with this case, where any `dynamic` get invoke in, there result must be a cast instead of `var` to avoid any misleading code – Tấn Nguyên Mar 26 '20 at 05:38

Tấn Nguyên · Answer 2 · 2020-03-12T08:47:04.080

I have spent almost 10 hours to upgrade 4.7 to 4.7.2, installed newest 16.4.6 VS, updated all dependencies, but still gets error.

So I finally end it up by change all var result to explicit (bool isMessage, string message) result. Just so sad that it can't get full real power of lambda tuple.

------ Update

I got what the bug is, because my parameter is passed as dynamic even IDE knew it was a string, but the var cannot.

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

My calling method

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);
}

It certainly is a bug of IDE and hope someone could raise the problem to developer.

Tuple lambda syntax suddenly not working in C#

2 Answers2

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