Passing containers between C# and C++

  • Thread starter Thread starter Kenneth Porter
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Kenneth Porter

How do I pass a container from C# to C++?

My client is writing an app in C# that needs to pass a collection of 3-
space vectors to my native C++ library. It will also need to read back the
collection.

In pure native C++, I'd just pass a "std::vector<MyType>&" where MyType is
an x/y/z vector (which might contain a std::vector<double>).

What's the portable C++/CLI equivalent that C# can easily deal with?

The passed container might hold from 10,000 to 100,000 objects.
 
Kenneth said:
How do I pass a container from C# to C++?

My client is writing an app in C# that needs to pass a collection of 3-
space vectors to my native C++ library. It will also need to read back the
collection.

In pure native C++, I'd just pass a "std::vector<MyType>&" where MyType is
an x/y/z vector (which might contain a std::vector<double>).

What's the portable C++/CLI equivalent that C# can easily deal with?

The passed container might hold from 10,000 to 100,000 objects.
Click to expand...

I would suggest a simple old fashioned array ...

Arne
 
I might misunderstand your requirement, but you could always use
List<List<int>^> or something (List from System::Collections::Generic).

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Kenneth said:
How do I pass a container from C# to C++?

My client is writing an app in C# that needs to pass a collection of 3-
space vectors to my native C++ library. It will also need to read back the
collection.

In pure native C++, I'd just pass a "std::vector<MyType>&" where MyType is
an x/y/z vector (which might contain a std::vector<double>).
Click to expand...

You can't pass native C++ objects over Dll boundaries (safely). You
would have to wrap the vector with a COM object or function interface,
which allows you to iterate through the vector.
What's the portable C++/CLI equivalent that C# can easily deal with?
The passed container might hold from 10,000 to 100,000 objects.
Click to expand...

Has been already answered by David A.

Each managed object can be directly accessed by C++/CLI and C#.

But for C++ perhaps the STL/CLR is more convenient. You must use VC 2008
however, since only this compiler ships with the STL/CLR.


Sample:

#include <cliext/vector>

public ref class CppObject
{
public:

CppObject()
{
vectorList = gcnew cliext::vector<int>();
// Add some values - for demonstr. purp. only
vectorList->push_back(10);
vectorList->push_back(20);
vectorList->push_back(30);

vectorList2.push_back(10);
vectorList2.push_back(20);
vectorList2.push_back(30);
}

cliext::vector<int>^ vectorList;
cliext::vector<int> vectorList2;
System::Collections::Generic::IList<int>^ GetCSharpCompatible();
System::Collections::Generic::IList<int>^ GetCSharpCompatible2();

}

System::Collections::Generic::IList<int>^ CppObject::GetCSharpCompatible()
{
return vectorList;
}

System::Collections::Generic::IList<int>^ CppObject::GetCSharpCompatible2()
{
// Returns a reference pointer on a member variable directly.
// Normally not a good idea to pass such objects
// over dll boundaries (depends -> on the lifetime of CppObject)
return %vectorList2;
}


Andre
 
How do I pass a container from C# to C++?

My client is writing an app in C# that needs to pass a collection of 3-
space vectors to my native C++ library. It will also need to read back the
collection.

In pure native C++, I'd just pass a "std::vector<MyType>&" where MyType is
an x/y/z vector (which might contain a std::vector<double>).

What's the portable C++/CLI equivalent that C# can easily deal with?

The passed container might hold from 10,000 to 100,000 objects.
Click to expand...

If the C++ application does not need to change the collection, and if
you need the best performance, you might consider using a managed
array - MyType[] - pinning it as you pass it to the C++ code. For a
more generic but slower solution, the receiving function should
declare its parameter as ICollection<MyType> or IList<MyType> -
whichever has all operations you need.
 
I might misunderstand your requirement, but you could always use
List<List<int>^> or something (List from System::Collections::Generic).
Click to expand...

Thanks, that sounds like the right thing.
 
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