ParallelFor

this is my solution for Parallel Letter Frequency Problem, You can find the full description of the problem in this link https://exercism.io/my/solutions/12020b7816e04e73b95de13d9814c35d, the unit test file taking from exercism.io, the problem description: Count the frequency of letters in texts using parallel computation.

To solve this problem i used Parallel.ForEach loop with partition-local variables

https://docs.microsoft.com/en-us/dotnet/standard/parallel-programming/how-to-write-a-parallel-foreach-loop-with-partition-local-variables