<TargetFrameworks> (plural) with custom MSBuild property from Directory.Build.props causes project to fail loading in IntelliSense

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
csharp, vscode
Domain
developer-experience, tooling

Research direction

Reproduce with Directory.Build.props and MyProject.csproj, then open a .cs file in VS Code and compare plural TargetFrameworks using the custom property with the literal and singular cases. Inspect the C# Dev Kit project-loading and IntelliSense path; done means project and referenced types resolve without CS0246 errors while dotnet build continues to succeed.

Written by the indexing model from the issue text.

Description

area-project-cps

Type: Bug

Issue Description

When a project uses <TargetFrameworks> (plural) and the TFM value is a custom MSBuild property defined in Directory.Build.props, C# Dev Kit fails to load the project correctly. All types from the project and its project references become invisible to IntelliSense, producing CS0246 errors throughout.

Steps to Reproduce

  1. Create Directory.Build.props at repo root:
<PropertyGroup>
  <MyWindowsVersion>net10.0-windows</MyWindowsVersion>
</PropertyGroup>
  1. Create MyProject.csproj:
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFrameworks>$(MyWindowsVersion)</TargetFrameworks>
    <UseWPF>true</UseWPF>
  </PropertyGroup>
</Project>
  1. Open in VS Code with C# Dev Kit, open any .cs file in the project

Expected Behavior

Project loads correctly. Types resolve, no errors.

Actual Behavior

Project fails to load correctly in IntelliSense. All types from the project and its project references are invisible, resulting in CS0246 errors throughout. dotnet build succeeds — this is an IntelliSense-only failure.

Element Value Loads correctly
<TargetFrameworks> plural custom property ❌
<TargetFrameworks> plural literal net10.0-windows ✅
<TargetFramework> singular custom property ✅

Workaround: use singular <TargetFramework>.

Related: dotnet/roslyn#39724, dotnet/roslyn#78144

Logs

C# log shows Successfully completed load even when the project fails to resolve types — no failure is logged at this level.

Environment Information

  • VSCode: 1.122.0
  • C# Extension: 2.140.8
  • C# Dev Kit: 3.20.199
  • Using OmniSharp: false
  • .NET SDK: 10.0.300

Extension version: 3.20.199
VS Code version: Code 1.122.0 (6a49527b96e326fe62fbdb56f60e16877c9aa724, 2026-05-27T14:03:01-07:00)
OS version: Windows_NT x64 10.0.26200
Modes:

System Info
Item Value
CPUs 12th Gen Intel(R) Core(TM) i9-12900H (20 x 2918)
GPU Status 2d_canvas: enabled
GPU0: VENDOR= 0x8086, DEVICE=0x46a6 [Intel(R) Iris(R) Xe Graphics], DRIVER_VENDOR=Intel, DRIVER_VERSION=32.0.101.7077 ACTIVE
GPU1: VENDOR= 0x10de, DEVICE=0x25b9 [NVIDIA RTX A1000 Laptop GPU], DRIVER_VERSION=32.0.15.7344
GPU2: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8246
Machine model name:
Machine model version:
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
skia_graphite: disabled_off
trees_in_viz: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off
Load (avg) undefined
Memory (System) 63.69GB (39.91GB free)
Process Argv --crash-reporter-id c75fc92f-81eb-45dd-8a76-059ea4ea7be1
Screen Reader no
VM 0%
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Avg merge
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Merged PRs (30d)
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