PR Summary

PowerShell can now get a .NET property whose override defines only the setter. The getter is inherited from the base property, as in C#.

Fix #25038

PR Context

For public override int Foo { set { ... } }, reflection returns a PropertyInfo for the override that has only the setter, although the getter is inherited. The .NET adapter used that PropertyInfo for getting too, so the property was treated as write-only:

• $obj.Foo threw WriteOnlyProperty.
• $obj.psobject.Properties['Foo'].Value and Select-Object Foo returned $null.
• Get-Member showed int Foo {set;}.

PropertyCacheEntry still stores the override's PropertyInfo, so setting, attributes and the declaring type don't change. Only for getting, when the override has no getter, it now uses the property that introduced the virtual property (found with MethodInfo.GetBaseDefinition()). That getter is virtual, so a getter override in a type in between is still called. ParameterizedPropertyCacheEntry takes the inherited getter the same way, so $obj.Item(1) works too, and the setter keeps the override's parameters. Protected properties used inside a PowerShell class are covered as well, because they also get a PropertyCacheEntry.

Other visible changes for these properties: $obj.Item(1) now calls the matching overload instead of another overload that has a getter, Get-Member shows an indexer as the base getter declares it, and Select-Object *, Format-List * and ConvertTo-Json now output their values.

In-box properties that become readable:

• XmlDocument.InnerText, XmlAttribute.InnerText and XmlAttribute.InnerXml. For example, ([xml]'<a>b</a>').InnerText returns $null today and b with this change.
• AnonymousPipeServerStream.ReadMode and AnonymousPipeClientStream.ReadMode.
• RSAOpenSsl.KeySize on Linux (### **Title:** Missing KeySize Reading Access in RSACertificateExtensions.GetRSAPrivateKey on Linux (.NET 9) dotnet/runtime#112622).
• On Windows: Site of ErrorProvider, AxHost and WebBrowserBase; HwndTarget.RootVisual.

Not changed:

• An override that defines only a non-public setter of a property with a public getter, for example public override int Foo { protected set { ... } }, used outside a PowerShell class that derives from the type. Reflection doesn't return such a property as public, so it isn't in the property table.
• Completion tooltips for types inferred without an instance still show { set; }, because CompletionCompleters reads the override's PropertyInfo itself.
• The opposite case: an override that defines only the getter of a property that has a setter. It has the same cause, so such a property can't be set from PowerShell (for example RSACryptoServiceProvider.KeySize), although C# can call the inherited setter. I left it out because the issue doesn't cover it, and it would make some properties settable that look read-only today.

I can handle the last two here or in separate PRs if you want them.

The new tests fail without the fix and pass with it.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge. If this PR is a work in progress, please open this as a Draft Pull Request and mark it as Ready to Review when it is ready to merge.
• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
    • Experimental feature name(s):
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed:
• Testing - New and feature
  • N/A or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed