How can I calculate string in single line?

Question

Example:
string input = "2+5*2"
string output = 12

Answer 1

https://www.codeproject.com/Articles/274093/Math-Parser-NET
There is explanation how to use.

Answer 2

I would avoid doing math on a string. Instead, convert your inputs to integers and then perform calculations. Conversion is a simple process already built into the C# libraries:

https://msdn.microsoft.com/en-us/library/system.int32.parse(v=vs.110).aspx