Minor performance improvements

[TheTrueColonel]

Made some changes that improve performance a small amount, but cut allocations by more than half.
Also changed the accessors and added readonly to help enforce .NET design guidelines.

Benchmarks between the current version and the updated version, using BenchmarkDotNet:

| Method        | Mean     | Error     | StdDev    | Gen0   | Gen1   | Allocated |
|-------------- |---------:|----------:|----------:|-------:|-------:|----------:|
| GetRequestOld | 5.334 us | 0.0151 us | 0.0212 us | 0.5493 | 0.0153 |  26.97 KB |
| GetRequestNew | 4.998 us | 0.0252 us | 0.0377 us | 0.2365 |      - |  11.62 KB |

[alex-jitbit]

awesome. reviewing asap