dotnet/roslyn

Strange behaviour in async method

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#32,276 opened on Jan 9, 2019

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Area-InteractiveBugDeveloper CommunityInteractive-Debugginghelp wanted

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Description

I have a solution targeting NetCoreApp2.0.

Lately I've seen that when running an async method, the debugger shows me variables that are non allocated (out of scope).

If this variable is an IQueryable<string> it will show show up in the 'Locals window' as NullReferenceException.

If I manually set the 'next statement' to first statement in the block containing this IQueryable<string>, a NullReferenceException will be thrown when accessing the variable.

This issue has been moved from https://developercommunity.visualstudio.com/content/problem/238451/strange-behaviour-in-async-method.html VSTS ticketId: 604787 These are the original issue comments: (no comments) These are the original issue solutions: (no solutions)

Contributor guide

Research direction
Examine the async method debugging and variable scope behavior in roslyn.
Tech stack
csharp
Domain
compilersdevtools
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60