What is the mathematical equivalent of numpy.where?

Question

I am porting a piece of python code that numpy currently uses for IronPython (the reasons for this are related to the specifics of the platform on which I am scripting).

Due to the incompatibility of numpy and IronPython, I need to replace each numpy function with its Math.NET equivalent, which I added as an external reference.

Being new to Math.NET, it's hard for me to find the equivalent of the numpy.where() function.

Any help would be appreciated!