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    <p>Consider using the explicit conversion to byte[] array. This way you explicitly specify where the struct is.</p> <p>In C you have:</p> <pre><code>extern "C" void FooBarCreate(FooBar* Data); extern "C" void FooBarUse(FooBar* Data) </code></pre> <p>In C# you write:</p> <pre><code> [DllImport("SomeFile.dll")] public static extern void FooBarCreate_DLL([In,Out] byte[] BufForFOOBAR); [DllImport("SomeFile.dll")] public static extern void FooBarUSE_DLL([In,Out] byte[] BufForFOOBAR); /// Call DLL with managed struct public static Int32 FooBarUse_Managed(ManagedFooBar Value) { byte[] ValueBuffer = StructureToByteArray(Value); return FooBarUse_DLL(ValueBuffer); } /// Get value from native DLL to managed struct public static void FooBarCreate_Managed(ref ManagedFooBar Value) { byte[] ValueBuffer = new byte[Marshal.SizeOf(Value)]; FooBarCreate_DLL(ValueBuffer); object TmpObj = new ManagedFooBar(); ByteArrayToStructure(ValueBuffer, ref TmpObj); Value = (ManagedFooBar)TmpObj; } </code></pre> <p>The native function is called directly by C#.</p> <p>The StructToByteArray and ByteArrayToStruct function are right here:</p> <pre><code>using System.Runtime.InteropServices; using System.Runtime.Serialization; public static byte[] StructureToByteArray(object obj) { int len = Marshal.SizeOf(obj); byte[] arr = new byte[len]; IntPtr ptr = Marshal.AllocHGlobal(len); Marshal.StructureToPtr(obj, ptr, true); Marshal.Copy(ptr, arr, 0, len); Marshal.FreeHGlobal(ptr); return arr; } public static void ByteArrayToStructure(byte[] bytearray, ref object obj) { int len = Marshal.SizeOf(obj); IntPtr i = Marshal.AllocHGlobal(len); Marshal.Copy(bytearray, 0, i, len); obj = Marshal.PtrToStructure(i, obj.GetType()); Marshal.FreeHGlobal(i); } </code></pre> <p>One last thing, the FooBarManaged (in C#):</p> <pre><code>[Serializable] /// Sequential - make sure C does uses the same struct member alignment [StructLayout(LayoutKind.Sequential, Pack=1)] public struct FooBarManaged { // Ususal POD field public Int32 ExpID; // Constant-sized string [MarshalAs(UnmanagedType.ByValArray, SizeConst=128)] public byte[] FileName; } </code></pre> <p>There's not much to tell about this code. I've used a simple autogenerator for this kind of marshalling to use the native sqlite3 backend as a data storage. Thus the need to marshal a lot of structs to and from C.</p>
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    1. USViktor Latypov
    1. USViktor Latypov
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    1. COI'm not sure I understand your suggestion. I have a third party library I can not modify. I have the header files, .dll and .obj files I can use. Are you suggesting I create a C-wrapper with the two functions you start off with? I thought the general "best practice" was to use a C++/CLI wrapper.
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      1. USHåkon K. Olafsen
    2. COYes, wrapping that library to support your (or my proposed) style is an option. That, of course, depends on the size of the 3rd party lib. In my case I was in charge of both parts.
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      1. USViktor Latypov
    3. COThis looks bogus to me.
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      1. USDavid Heffernan
 

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