Swap Dictionary<K, V> with HashSet<XamlMember>, avoid double lookup

[h3xds1nz]

Description

Replaces XamlPropertySet which is just a wrapped Dictionary<XamlMember, bool> with HashSet<XamlMember> for improved performance and decreased allocations. The conditions under which this was written do no longer apply.

Also avoids double lookup on each addition.

Customer Impact

Improved performance, decreased allocations.

Regression

No.

Testing

Local build.

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 11.20973%. Comparing base (72af9a5) to head (37491a8).
Report is 7 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #10750         +/-   ##
===================================================
- Coverage   11.25778%   11.20973%   -0.04805%     
===================================================
  Files           3315        3315                 
  Lines         665229      665217         -12     
  Branches       74668       74667          -1     
===================================================
- Hits           74890       74569        -321     
- Misses        589035      589350        +315     
+ Partials        1304        1298          -6     

Flag	Coverage Δ
Debug	11.20973% <0.00000%> (-0.04805%)	⬇️

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