# Large string addition subtraction ?

I have two very long strings (150-250 digits) I need to perform math addition subtraction.

string a = "111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111";
string b = "222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222";
string c = "33333333333333333333";

string Finished = a - b + c;

These are the longest/largest numbers I've ever worked with, so I don't know if I should covert them before processing math.

I recieve this compile error:  Operator '-' cannot be applied to operands of type 'string' and 'string'
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Middle School Assistant TeacherCommented:
Take a look at this project entitled "C# BigInteger Class":
http://www.codeproject.com/csharp/biginteger.asp
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Commented:
in 'addition', with C# the + operator, operating on strings does CONCATENATION, not 'addition' - with strings, even if made up of digits, the Strings will be APPENDED, not converted to numbers and the ADDED.

with

string b = "222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222";
string c = "33333333333333333333";

b+c = "22222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222233333333333333333333"

not

"222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222255555555555555555555"

I do not know of any 'native' C# workspaces that can deal with 150 -250 digit INTEGERS.  What are you doing that requires the use of such large numbers?

AW

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