Code Quality: Use concrete types when possible for improved performance

[gumbarros]

Resolved / Related Issues

• Were these changes approved in an issue or discussion with the project maintainers? In order to prevent extra work, feature requests and changes to the codebase must be approved before the pull request will be reviewed. This prevents extra work for the contributors and maintainers.
  Related to Code Quality: Fix CA1859 and CA1829 #14955

Validation
How did you test these changes?

• Did you build the app and test your changes?
• Did you check for accessibility? You can use Accessibility Insights for this.
• Did you remove any strings from the en-us resource file?
  • Did you search the solution to see if the string is still being used?
• Did you implement any design changes to an existing feature?
  • Was this change approved?
• Are there any other steps that were used to validate these changes?
  1. Open app ...
  2. Click settings button ...

It's the same of CA1859, but I ran all Rider analyzers in the solution and found CA1859 in another name.

[0x5bfa]

lgtm

[d2dyno1]

The performance impact is negligible, but it looks ok
LGTM