How to use a variable to store a big unsigned integer (76 digits)?

I am currently encountering a problem to convert the uint256 variable in solidity to C# for storage. I tried double.parse(), and it will be converted to scientific notation and rounded or unconditional, resulting in my numerical error , although I can use string to solve this problem, but I think it is not the fundamental way. The maximum value is 115792089237316195423570985008687907853269984665640564039457584007913129639935 won't get any bigger than this