How do I know which .NET assembly to load when I get the "Unable to resolve the name" error?

I'm trying to use the System.IO.MemoryMappedFiles.CreateNew method to create a memory-mapped file, so I can create shared memory for inter-process communication. I loaded the System.IO.MemoryMappedFiles assembly, but I'm getting an "Unable to resolve the name" error when I use the method. 

>> NET.addAssembly('System.IO.MemoryMappedFiles') 
>> memMapFile = System.IO.MemoryMappedFiles.MemoryMappedFile.CreateOrOpen('mySharedFile', 1024) 
Unable to resolve the name 
'System.IO.MemoryMappedFiles.MemoryMappedFile.CreateOrOpen'. 

How can I access this method? 

Answer 1

[MathWorks Support Team]

Generally, this error indicates that the required assembly is missing. In this example, if you are getting this error, then  it means that MATLAB is set up for .NET Framework, which requires the System.Core assembly to run this method. Loading the System.IO.MemoryMappedFiles assembly would be appropriate if you are using .NET Core. You can use the dotnetenv function in MATLAB to display or set the version of .NET.  

In general, when using .NET Base classes and methods you may need to load an assembly, but the assembly to load may depend on what version of .NET you are using:  Framework or Core. The steps below illustrate how to determine what assembly is required and how to load an use it.

Determine the required assembly 

Follow the steps below to determine which assembly to load for your Base class.

1.  Go to the .NET Microsoft API documentation

2. Select the .NET API and .NET version. For example, ".NET Version 8" or ".NET Framework Version 4.8".

3. Enter the name of the class that you want to use in the search bar (e.g, System.IO.MemoryMappedFiles.MemoryMappedFile) and select the appropriate link to go to the class documentation. 

4. On the class documentation page note the assembly and namespace listed in the" Definition" section. If more than one assembly is listed, either one can be used. 

Load the assembly and use a class

Run the following code in MATLAB to load the assembly and use the MemoryMappedFile class.

% Add assemblies and import namespaces 
% .NET Core and Framework require different assemblies for the MemoryMappedFiles class
env = dotnetenv; 
if (env.Runtime == "framework") 
    NET.addAssembly('System.Core'); 
else 
    % For example, the assembly required for .NET Core 8
    NET.addAssembly('System.IO.MemoryMappedFiles'); % or netstandard 
end 

% Create or open a MemoryMappedFile 
memMapFile = System.IO.MemoryMappedFiles.MemoryMappedFile.CreateOrOpen('mySharedFile', 1024) 

In the example code above, you can see that .NET Framework requires the System.Core assembly, and .NET Core 8 requires the System.IO.MemoryMappedFiles (or netstandard) assembly.