Install the Right .NET Runtime for an App That Will Not Start

**dotnet --list-runtimes** lists the modern runtimes; the registry key lists the .NET Framework 4.x version. An app needs one of the two, not both.

dotnet --list-runtimes
dotnet --list-sdks
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full' -ErrorAction SilentlyContinue | Select-Object Version,Release

The runtimeconfig.json names the framework and the version for a modern app, and the manifest names the Framework version for a 4.x app. That file is the answer, not the error text.

Get-ChildItem 'C:\Program Files\App' -Filter *.runtimeconfig.json -Recurse -ErrorAction SilentlyContinue | Select-Object FullName
Get-Content 'C:\Program Files\App\App.runtimeconfig.json' -ErrorAction SilentlyContinue
Get-Content 'C:\Program Files\App\App.exe.config' -ErrorAction SilentlyContinue | Select-String -Pattern 'supportedRuntime|targetFramework'

**Event Viewer** records the .NET runtime error with the exception and the assembly name. A missing assembly is a different problem from a missing runtime.

Get-WinEvent -LogName Application -MaxEvents 100 | Where-Object ProviderName -match '\.NET Runtime|Application Error' | Select-Object TimeCreated,Id,Message -First 3
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Compatibility Assistant\Store' -ErrorAction SilentlyContinue | Select-Object * -ExcludeProperty PS*

An end user needs the runtime. The SDK adds compilers and is the wrong download for a machine that only runs the app.

winget search Microsoft.DotNet.Runtime
winget install --id Microsoft.DotNet.Runtime.8 --silent --accept-package-agreements --accept-source-agreements
dotnet --list-runtimes

**.NET Framework 3.5** is an optional Windows feature, not a download. An app that targets 2.0 or 3.5 needs that feature enabled.

Get-WindowsOptionalFeature -Online -FeatureName NetFx3 | Select-Object FeatureName,State
Enable-WindowsOptionalFeature -Online -FeatureName NetFx3 -All -NoRestart
Get-WindowsOptionalFeature -Online -FeatureName NetFx3 | Select-Object State

Start it from its own folder, not from a shortcut, so the working directory matches. A missing DLL next to the exe is a deployment problem, not a runtime one.

Push-Location 'C:\Program Files\App'
.\App.exe
Pop-Location
Get-Process App -ErrorAction SilentlyContinue | Select-Object Name,Id,StartTime
Get-WinEvent -LogName Application -MaxEvents 10 | Where-Object ProviderName -match '.NET' | Select-Object TimeCreated,Message -First 2