(Solved) : Need Help Program Need Able Sum Strings Also Summing Two Decimal Values Result Must Decima Q26782481 . . . .

I need help with this program. I need it to be able tosum strings and also when summing two decimal values, the resultmust be decimal as well. It does identify the tokens,basically reads them and implement them through mathematicalcalculations, but with strings it doesn’t work. C programs startsbut once you input a statement it explodes, but when u use a wordwith assignment in the entrance, everything else works,ADD,SUB,etc.It all depends on what u input at the beginning of thestatement. 

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Assemblyinfo.cs

using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

// General Information about an assembly is controlledthrough the following 
// set of attributes. Change these attribute