Proposal: Bring C# 9 "Init-Only" properties to XAML

[ryandemopoulos]

Proposal: C# 9 "Init-Only" properties in XAML

Init-only properties are a set-on-initialization-only accessor in C# 9. Morten has suggested that we bring this to XAML: https://twitter.com/dotMorten/status/1263284520364564481

Interesting idea to explore. It would allow the instantiation of read-only / immutable values in XAML markup.

Summary

Unsure if this would require a syntax change/expansion in XAML...?

Rationale

(it would be great if Morten or others could articulate additional rationale & scenarios here--I'm just blitzing Twitter notifications right now so doing light initial job on this proposal)

• {First reason for why we should consider this proposal}
• {Second reason for why we should consider this proposal}
• {etc}

Scope

Capability	Priority
This proposal will allow developers to accomplish W	Must
This proposal will allow end users to accomplish X	Should
This proposal will allow developers to accomplish Y	Could
This proposal will allow end users to accomplish Z	Won't

Important Notes

Open Questions

[MikeHillberg]

Big fan of this. The Xaml 2009 spec has an x:Arguments syntax for this, allowing you to pass arguments to the constructor:

https://docs.microsoft.com/en-us/dotnet/desktop-wpf/xaml-services/xarguments-directive

[Trolldemorted]

Are there any workarounds for this execpt "go through all your dataclasses and remove the immutability"?