Thank you!!!

Define "doesnt work". You should use Console.WriteLine.

Either use System.Console.WriteLine() or write using System; before your code.

is there a way to debug using c#? Console.WriteLine(smth) doesnt work

You are right, must be related to update of framework. Check the fork for a new valid solution.

Will be better if you just give better names for your variables.

Solution is not running.

A number can't start with 0, 1 to 4 are already there, so the lowest possible digit is 5.

Answer for runes = '3231+-?8177=-?4946' : 0 should equal 5

This is funny. No matter if I change the answer from 0 to 9 except 5, the answer would still be 5 lmao.

You can debug your code by sending messages to STDOUT.

Don't show the entry string when failed. How to understand the bug? ====>
Test Results:
RunesTest
EdgeCase
Test Failed
Expected: 8
But was: 0
Completed in 68.4420ms
testAddition
Test Failed
Expected: 0
But was: -1
Completed in 0.9640ms
testMultiplication
Test Failed
Expected: 0
But was: -1
Completed in 0.7850ms
testRandom
Test Failed
Expected: 3
But was: -1
Completed in 1.3650ms
testSubtrastion
Test Failed
Expected: 0
But was: -1
Completed in 0.7180ms
Completed in 79.3880ms

So? Please read the note at the end of the description.

This solution doesn't work when other letters are used. Like {"n","s","n","s","n","s","n","s","a","a"}.