Where has BigInt gone? [duplicate]

This question already has answers here: Where is my System.Numerics nam开发者_运维问答espace? (2 answers) Closed 10 years ago.

I have started on the Project Euler problems. Currently I am on Problem 13 which requires you to provide the first ten digits of the sum of 100, 50 digit numbers.

I decided I would try to solve it with a big int class in C#. I looked around on the internet and there are tons of example code with them. However, I can't seem to find BigInt in my Visual Studio 2010.

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In the .NET Framework 4.0 it's found in System.Numerics.dll. Add a reference to that assembly to gain access to System.Numerics.BigInteger.