[v11][maui] csproj intellisense shows warning when <TargetFrameworks> has only one value

[mauroa]

Describe the issue

When opening a MAUI project and the csproj file in the editor, a problem is reported because intellisense fails when has only one default value. This is by default on the MAUI template since the rest of the target frameworks are included conditionally. See:

<TargetFrameworks>net11.0-android</TargetFrameworks>
<TargetFrameworks Condition="!$([MSBuild]::IsOSPlatform('linux'))">$(TargetFrameworks);net11.0-ios;net11.0-maccatalyst</TargetFrameworks>
<TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net11.0-windows10.0.19041.0</TargetFrameworks>

Warning displayed (MSBLSP004 and MSBLSP009 warning on the Problems tab when opening the csproj):

'1' is not a valid version value.
Use <TargetFramework> (singular) when targeting a single framework

Collect logs

csdevkit-logs-2026-08-24T16-09-45.zip

Steps to reproduce

1. Create a new MAUI app
2. Open the csproj
3. Open the Problems tab, and notice that there's MSBLSP004 and MSBLSP009 warning

Expected behavior

Opening the csproj file should not produce any warnings or errors

Environment information

• VSCode: 1.136.0-insider (Universal)
• .NET SDK: 11.0.100-preview.7.26381.103
• MAUI: 11.0.0-preview.7.26403.4

Extension:

• NET MAUI: 1.17.228-g7a01fb0c71
• C# Dev Kit: 9.9.462-gf055a7
• C#: 2.151.17

[LittleLittleCloud]

[copilot] RCA investigation: this report contains two independent MSBuild language-service false positives.

1. TargetFrameworkAnalyzer reports MSBLSP004 whenever a literal <TargetFrameworks> value contains no semicolon. The MAUI template's first declaration is intentionally a single base TFM, followed by conditional sibling declarations that append $(TargetFrameworks). The analyzer evaluates each element in isolation and misses that valid aggregate pattern.
2. MSBLSP009 for value 1 comes from schema precedence. MAUI.buildschema.json correctly declares ApplicationVersion as Int, but MSBuildDocumentState constructs CompositeSchema with the generic generated schemas before applicable MAUI schemas. First-match lookup therefore selects the generic ApplicationVersion: Version definition, and ValueTypeValidator rejects 1 because its version regex requires at least major.minor.

Recommended fixes: make applicable SDK schemas override generic schemas, with collision tests for MAUI properties; and suppress the singular/plural suggestion when conditional sibling TargetFrameworks declarations append to the property. Add the exact stock MAUI project fragment as a regression test for both diagnostics.

[drewnoakes]

https://devdiv.visualstudio.com/DevDiv/_git/vs-green/pullrequest/775626

[drewnoakes]

PR merged

[emaf]

This is already fixed in the 11.0.2 prerelase.