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    <p>Here's what I would start with.</p> <p>Usage:</p> <pre><code>IFoo foo = UnsafeNativeMethods.GetFooInterface(); foo.Method1(0, 1.0f); </code></pre> <p>Implementation:</p> <pre><code>internal interface IFoo { void Method1(int a, float b); void Method2(int a, float b, int c); } internal static class UnsafeNativeMethods { public static IFoo GetFooInterface() { IntPtr self = GetInterface(InterfaceType.Foo); NativeFoo nativeFoo = (NativeFoo)Marshal.PtrToStructure(self, typeof(NativeFoo)); return new NativeFooWrapper(self, nativeFoo.Method1, nativeFoo.Method2); } [DllImport("mydll.dll", EntryPoint = "getInterface", CallingConvention = CallingConvention.Cdecl)] private static extern IntPtr GetInterface(InterfaceType id); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate void Method1Delegate(IntPtr self, int a, float b); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate void Method2Delegate(IntPtr self, int a, float b, int c); private enum InterfaceType { Foo, Bar } private struct NativeFoo { public Method1Delegate Method1; public Method2Delegate Method2; } private sealed class NativeFooWrapper : IFoo { private IntPtr _self; private Method1Delegate _method1; private Method2Delegate _method2; public NativeFooWrapper(IntPtr self, Method1Delegate method1, Method2Delegate method2) { this._self = self; this._method1 = method1; this._method2 = method2; } public void Method1(int a, float b) { _method1(_self, a, b); } public void Method2(int a, float b, int c) { _method2(_self, a, b, c); } } } </code></pre>
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    1. POC# P/Invoke: Marshalling structures containing function pointers
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    1. USSam Harwell
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    1. COWell, this is how I'm doing it. It's just that this kind of "pretty-wrapping" was irrelevant to the question. Then I know I didn't explain that in details, but `self` is not the pointer to the interface structure. It's really a `this` pointer.
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      1. USGregory Pakosz
    2. COThe native library has a `void* obj = createObject(int type)` entry point. You use it to instantiate types, then if the type you instantiated implements the IFoo interface (`bool implements(void* obj, int iface)` returns `true` for `obj` and `FOO`), you are allowed to call `((IFoo*)getInterface(FOO))->method1(obj, 0, 1.0f);`
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      1. USGregory Pakosz
    3. COThis simplest alteration would be adding an `IntPtr self` parameter to `GetFooInterface`. For a complex wrapper like that, I'd actually create `Is<TInterface>` and `As<TInterface>` methods to perform the casts. If I went a step further, I'd dynamically create implementation classes so the C# `is` and `as` operators work seamlessly.
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      1. USSam Harwell
 

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