We know that .NET framework class encapsulate the Win32 API, now I am wondering how the .NET framework class call Win32 API?
Ways I know so far:
Through P/Invoke
VC++/CLI
Both 1 and 2
Anybody know the answer?
Most framework classes use P/Invoke if they need to call unmanaged APIs. Fire up Reflector on System.Windows.Forms and you'll see classes called NativeMethods and UnsafeNativeMethods which do a lot of P/Invoke. Similarly System.Drawing has a SafeNativeMethods class which declares all the GDI+ P/Invokes.
The other main interop method you don't mention is COM interop. I don't know how widely this is used within the framework, but I'd guess that some of the WMI (System.Management) stuff uses it pretty heavily, plus of course WinForms ActiveX support.
Related
Is there a smart way to scaffold a COM callable .NET class library from an existing native COM DLL?
Scenario
Suppose you have a COM based C++ Win32 application and you want to replace one of the COM DLLs with something written from scratch.
Constraints
The new library shall be written in C#, targeting the .NET Framework (4.x)
No modifications to the rest of the existing unmanaged application shall be required.
No recompilation of the unmanaged code shall be required.
What I already know
You can create .NET assemblies which are COM callable.
You can import the type library IDL from an existing COM DLL.
Based on this question, what I want should be possible, even if arduous.
Question
Is there a smart / efficient way to generate the scaffolding code for a COM callable .NET class library with the exact same signature as an existing unmanaged COM DLL so I can replace the DLLs?
There does not need to be any implementation at first, every method could just throw a NotImplementedException for example.
Has anybody tried to use C++/winrt to create Win32 COM objects? The C++/winrt docs document that consuming them is possible and of course creating "new" UWP COM objects. I was wondering if for some simple scenario's one could use the C++/winrt headers instead of ATL to generate some simple COM objects.
You can write a COM component with C++/WinRT. Here’s an example of a COM executable server but the principles and techniques are much the same for a DLL.
https://gist.github.com/kennykerr/d983767262118ae0366ef1ec282e428a
For a DLL you just want to make sure you export an implementation of DllGetClassObject and DllCanUnloadNow. Otherwise, its just like any other DLL and you can use the winrt::implements class template to implement the various classes and factories.
I am working on C++/CLI Wrapper for C Static Library.Static Library has 10 function in it.
THis C++/CLI Wrapper will Expose 10 API to C# Application.The Wrapper Will be in the Form of dll.
The Wrapper Will be Used in C# Application.
Now I am trying to add a class in C++/CLi application which will expose function to C# application I am getting Many Option like
C++ Class
CLR Class
a. Component Class
b.Installer Class
c. Windows Form
d. Installer Class
I am bit confused which I need to select out of it as I am new bee in C++/CLI
You need a
CLR Class - Component
since it can be consumed by .NET clients.
CLR class is declared as follows
ref class Wrapper {....}
However in your scenario you could also write a dynamic library and pinvoke the methods from .NET client.
Not sure if your question has been entirely answered, but a Component class creates a class that implements an IComponent interface for remoting/ inter process communication purposes. Didn't seem like what you were looking for.
I think what you were looking for i just a "template" to create a managed class?
In that case all you need to do is select C++ in the wizard and make sure the "Managed" check box on the right hand side is selected.
I want to expose a C++ library to a C# application and I decided to take the C++/CLI wrapper approach instead of P/Invoke. The problem that I am now facing is how to expose a templated class in the C++ lib to the C# application using generics.
On the C++ side I have:
template <typename T> class Someclass;
And my goal is to be able to expose the following type to the C# app
class Someclass<T> {}
So the question now is how should my C++/CLI wrapper look like. I tried the naive approach and created a templated type in C++/CLI and naturally I wasnt able to instantiate the class in C# with generic parameters. And if I expose the class as a generic class I wont be able to pass it to C++.
Disclaimer: I am a C++ newbie so please be gentle :)
I am familiar with the differences between generics and templates so no need to explain those. I have this bad feeling that what I want isn't doable, but since I am relatively new to C++ I hope I can somehow achieve it.
AFAIK: You'll have to write a C++ generic.
http://www.codeproject.com/KB/mcpp/cppcligenerics.aspx
I don't see how the C# application would even understand the template being as that is calculated at compile time, so the C# application wont see templates in the DLL.
Is there any way I can reference and use classes and methods from a managed .net assembly from within a totally unmanaged C++ application? (no /clr)
Absolutely, and this gem from CodeProject should prove helpful
You need a CCW (COM callable wrapper).
You can - by hosting the CLR. I found one set of example code here . I have no way of knowing how good the advice there is though, as I've never done it.
You can expose the .NET class thru COM and consume the classes thru COM.