fix: add JSON fallback for SaveWindowPosition on .NET 9#4567
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JyslaFancy wants to merge 5 commits into
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fix: add JSON fallback for SaveWindowPosition on .NET 9#4567JyslaFancy wants to merge 5 commits into
JyslaFancy wants to merge 5 commits into
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added 5 commits
June 7, 2026 15:52
- ApplicationSettingsBase.Save() fails on .NET 9 < 9.0.3 due to a runtime bug (dotnet/runtime#112410) where ClientConfigurationHost receives an empty path on UNC/network locations. - SaveWindowState() now saves a JSON backup to %LocalAppData% as a fallback when the settings save fails. - LoadWindowState() tries the JSON fallback when settings reload fails or returns an empty placement. - On successful save via ApplicationSettingsBase, the JSON backup is also updated to stay in sync. Fixes MahApps#4541
System.Text.Json is not available on .NET Framework 4.6.2. Wrap JSON fallback code with #if !NET462 to maintain compatibility with legacy target framework.
Merge the two identical null/empty checks into one to eliminate Codacy warning about redundant condition.
Capture settings.Placement in a local variable so the compiler can track null-state through the #if blocks. Prevents CS8602 on placement.ToWINDOWPLACEMENT().
Compiler nullable flow analysis can't track through #if blocks and out-parameter narrowing. placement is guaranteed non-null after the if-check (we return in all null branches).
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Description
Fixes #4541 — .NET 9 breaks SaveWindowPosition in MetroWindow.
Problem
On .NET 9 prior to version 9.0.3, ApplicationSettingsBase.Save() throws a
ConfigurationErrorsException when the project path is on a UNC/network location.
This is a known .NET runtime bug (dotnet/runtime#112410), fixed in .NET 9.0.3.
Fix
Adds a JSON-based fallback for window placement persistence:
%LocalAppData%//WindowPlacement/.json
No new dependencies — uses System.Text.Json.