CODEWITHSUNDEEP
c#c++-cli
Ashutosh
Ashutosh

Reputation: 397

How do I call a function defined in a C++ DLL that has a parameter of type int *, from inside C# code?

I have a native regular C++ Dll which I want to call from C# code, so i created C++/CLI class (as described here and here) which will include managed C++ code and which can be called by any C# code directly and which can make calls inturn to native unmanaged C++.

One of function in native C++ dll has parameter of type int *. How do I declare in wrapper function and how can i convert it into int *?

Upvotes: 2

Views: 726

Answers (2)

plinth
plinth

Reputation: 49209

[DllImport("some.dll")]
static extern void SomeCPlusPlusFunction(IntPtr arg);

IntPtr is a type that is roughly equivalent to void *.

From your comment, you'd be best off doing something like this (C#):

int size = 3;
fixed (int *p = &size) {
    IntPtr data = Marshal.AllocHGlobal(new IntPtr(p));
    // do some work with data
    Marshal.FreeHGlobal(data); // have to free it
}

but since AllocHGlobal can take an int, I don't know why you wouldn't do this:

IntPtr data = Marshal.AllocHGlobal(size);

Upvotes: 2

Hans Passant
Hans Passant

Reputation: 942508

It is the C/C++ way of passing a value by reference. You should use the ref or out keyword:

[DllImport("something.dll")]
private static extern void Foo(ref int arg);

In C++/CLI that would look roughly like this:

public ref class Wrapper {
private:
    Unmanaged* impl;
public:
    void Foo(int% arg) { impl->Foo(&arg); }
    // etc..
};

Upvotes: 5

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