问题
I\'m using Visual Studio 2010 and trying to use the BigInteger type in a C# program. This type is supposed to be available in System.Numerics namespace, but I don\'t seem to have that installed in the .Net 4.0 framework. When I type \"using System.Numerics;\" in VS2010, a red underline appears under the \"Numerics\". Has anyone else ever had this problem?
If so, how do you resolve it? I just re-downloaded and re-installed (repaired) the .Net 4.0 framework, but that didn\'t help. I\'ve never had any problems with other C# programs that I\'ve written, so I\'m wondering what I\'m missing.
回答1:
You need to add an assembly reference to System.Numerics.dll
The MSDN entry on BigInteger states:
BigInteger Structure
...
Namespace: System.Numerics
Assembly: System.Numerics (in System.Numerics.dll)
回答2:
Though most assemblies are the part of the installation, VS does add only some core elements to the reference list of a project (Core, Data, XML etc.). One needs to add other references by hand using Reference Manager.
Right-click your project, then select Add Reference (or Add->Reference). System.Numerics resides in Assemblies. Then you can use using System.Numerics; in project files.
PS: this answer is not intended to get any vote. It is only for future reference if someone needs how to do it, just as I needed before this answer.
来源：https://stackoverflow.com/questions/4820953/where-is-my-system-numerics-namespace