NET assembly unload conundrum

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Paul Kelly
Paul Kelly on 9 Apr 2013
Commented: Roofus Milton on 15 Nov 2019
I am trying to develop a C# class in Visual Studio and test it in Matlab. I can load the NET assembly and use it okay, but a problem arises if I change the NET code.
If I load the NET assembly into Matlab from the Visual Studio debug folder I can't rebuild the assembly in Visual Studio.
If I copy the dll into a local folder and load into Matlab from there I can only load once. Subsequent times I get the following error: "The process cannot access the file because it is being used by another process." In other words it won't let me copy the new dll because the old one is still in use.
So at the moment if I change the assembly code I have to close Matlab and reopen it to test the new assembly. This is adding quite a lot of time to my development.
I believe my version of Matlab (2010a) cannot unload NET assemblies. Does anyone know of another way around this?

Accepted Answer

Fab on 19 Jul 2013
According to Matlab's support rebooting is the only solution to this problem for the current Matlab Version (, R2013a):
"The ability to unload an assembly is not available in MATLAB at this point of time. This may be addressed in one of the future releases. Currently, to work around this issue, restart MATLAB."

More Answers (5)

Cameron on 2 Feb 2016
I am also having this same problem with R2015b. Any resolution??

Ivan on 19 Jul 2016
The same problem in R2016a

imme werus
imme werus on 24 Apr 2017
Edited: imme werus on 24 Apr 2017
I think it is also the same for 2016b, is that true ?

Markus Finkeldey
Markus Finkeldey on 10 Oct 2017
Edited: Markus Finkeldey on 10 Oct 2017
It seems that the .NET support of Matlab is very limited even in R2017a, makes it a hell of a workload if you want to access a c# library instead of a pure c library.
  1 Comment
Paul Kelly
Paul Kelly on 10 Oct 2017
True. For me the real issue was that because I was developing C# applications and testing them using Matlab, every time I made a change I had to restart Matlab. The answer was to find other ways to test the C# code. It was a pity because Matlab gave me a lot of possibilities.

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Travis Leith
Travis Leith on 30 Oct 2019
This is still an issue going into 2020 :(
Roofus Milton
Roofus Milton on 15 Nov 2019
Yup. Wolfram has great integration. I suspect their approach creates a new AppDomain and subsequently loads the requested assemblies. LINQPad has remained my default testing tool.

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