DllNotFoundException: Unable to load DLL 'google-ortools-native': The specified module could not be found. (Exception from HRESULT: 0x8007007E

[shaileshgande]

What version of OR-Tools and what language are you using?
Version: 9.10.4067
Language: C#

Which solver are you using (e.g. CP-SAT, Routing Solver, GLOP, BOP, Gurobi)
GLOP

What operating system (Linux, Windows, ...) and version?
Windows 11

What did you do?
Steps to reproduce the behavior:

1. Create a console .NetFramework project targeting 4.6.2 version
2. Install Google.Ortools via the Nuget package manager
3. Use the "Solver.CreateSolver("GLOP")" line to get the solver object.
4. Runtime exception is thrown:

System.TypeInitializationException: 'The type initializer for 'Google.OrTools.LinearSolver.operations_research_linear_solverPINVOKE' threw an exception
Inner exception 1:
TypeInitializationException: The type initializer for 'SWIGExceptionHelper' threw an exception.
Inner Exception 2:
DllNotFoundException: Unable to load DLL 'google-ortools-native': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

What did you expect to see
Able to the solver object

What did you see instead?
runtime exeception

Note:
Nuget pacakage manager shows that the ortools package has dependency with .net framework 4.6.2.
So, ideally it should work with .net 4.6.2 and above

[Mizux]

IIRC net4.6.2 framewrok don't know how to parse project.csproj native library stuff so you need to load it manually...

related to:

• Missing support for .NET Framework in latest Nuget packages #3503
• Can't load or-tools 9.6 library on windows, .NET6 #3747 (comment)

note: Pet project to test combinatory:
https://github.com/Mizux/dotnet-native/actions/runs/10811556739

[Mizux]

Can you target .Net CORE instead ? i.e. net6.0 (LTS) or net8.0 (LTS) instead ?

ref:
https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core
https://dotnet.microsoft.com/en-us/platform/support/policy

[shaileshgande]

Thanks! @Mizux for the response!
Loading the dll 'google-ortools-native.dll' manually helped to resolve the exceptions in .net framework.
However, additionally the prefer-32 bit checkbox had to be unchecked for me to resolve the 'BadImageFormat' exception.

• Google.OrTools exception C# framework 4.7.2 #1185

Quick question:
Is there any other way than loading the dll manually to able to work with a .Net Framework application?
note: I cannot target .net core or .net 6.0 or above.

[Mizux]

very long time ago we also shipped a runtime.json, maybe for .Net Framework user this one is mandatory to locate the runtime file ?
https://github.com/google/or-tools/blob/v6.10/ortools/dotnet/Google.OrTools/runtime.json.in

Will try to do some test in Mizux/dotnet-native project ASAP...

[martinfires]

Thanks! @Mizux for the response! Loading the dll 'google-ortools-native.dll' manually helped to resolve the exceptions in .net framework. However, additionally the prefer-32 bit checkbox had to be unchecked for me to resolve the 'BadImageFormat' exception. (#1185)

Quick question: Is there any other way than loading the dll manually to able to work with a .Net Framework application? note: I cannot target .net core or .net 6.0 or above.

Thank you @shaileshgande

Finally it helped me to. File google-ortools-native.dll must be taken from: @SolutionRoot@\packages\Google.OrTools.runtime.win-x64.9.11.4210\runtimes\win-x64\native
and copied into @SolutionRoot@\bin\Debug.

Prefer 32-bit checkbox is in (Debug or Release) properties\Build\Prefer 32-bit, must be unchecked.

Then everything works on .NET Framework 4.6.2