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POPassing structure containing an array of structures between C and C# (DLL and P invoke)
 

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  1. POPassing structure containing an array of structures between C and C# (DLL and P invoke)
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    <p>I have C dll with some complicated struct and I ma really a newbie in C#:</p> <pre><code>typedef struct { int a; int b; } simple_struct; typedef struct { int d; int e; simple_struct f[20]; short g; simple_struct h[20]; short i; } complex_struct; </code></pre> <p>The issue is that I am not able to interface my C# application with this structure!!</p> <p>In the DLL there is a function GetData(complex_struct* myStruct) and I shoud call it from C#, so I created:</p> <pre><code> [StructLayout(LayoutKind.Sequential, Pack = 1)] unsafe struct simple_struct { public int a; public int b; } ; [StructLayout(LayoutKind.Sequential, Pack = 1)] unsafe struct complex_struct { public int d; public int e; public simple_struct[] f; public short g; public simple_struct[] h; public short i; } ; </code></pre> <p>but the problem is that when I pass complex_struct as argument of GetData, all the fields are filled back form me, but not my two array of simple_struct (I mean f and h)!! Their values are null!!</p> <p>Can some one help me please, thanks</p> <hr> <p>Hi and thanks for your reply, </p> <p>I have done like what you said, but I still have another issue when I call GetData, the process crashes without any message (a kind of Exception):</p> <p>This is my C sharp code: namespace dll_test_import_c_sharp { class Program { [StructLayout(LayoutKind.Sequential, Pack = 1)] struct simple_struct { public int a; public int b; } ;</p> <pre><code> [StructLayout(LayoutKind.Sequential, Pack = 1)] struct complex_struct { public int d; public int e; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)] public simple_struct[] f; public short g; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)] public simple_struct[] h; public short i; } ; [DllImport("test_dll.dll", CharSet = CharSet.Unicode)] static extern int GetData(ref complex_struct a); static void Main(string[] args) { complex_struct a = new complex_struct(); GetData(ref a); return; } } } </code></pre> <p>I have done a lot of printf i GetData and all of them are well executed, it seems like the 'return' instruction crashes!! </p> <p>I tried to call GetData by ref or by out and both of them don't work...</p> <hr> <p>Hi and thanks for your reply, </p> <p>I have done like what you said, but I still have another issue when I call GetData, the process crashes without any message (a kind of Exception):</p> <p>This is my C sharp code: namespace dll_test_import_c_sharp { class Program { [StructLayout(LayoutKind.Sequential, Pack = 1)] struct simple_struct { public int a; public int b; } ;</p> <pre><code> [StructLayout(LayoutKind.Sequential, Pack = 1)] struct complex_struct { public int d; public int e; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)] public simple_struct[] f; public short g; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)] public simple_struct[] h; public short i; } ; [DllImport("test_dll.dll", CharSet = CharSet.Unicode)] static extern int GetData(ref complex_struct a); static void Main(string[] args) { complex_struct a = new complex_struct(); GetData(ref a); return; } } } </code></pre> <p>I have done a lot of printf i GetData and all of them are well executed, it seems like the 'return' instruction crashes!! </p> <p>I tried to call GetData by ref or by out and both of them don't work...</p>
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      1. POPassing structure containing an array of structures between C and C# (DLL and P invoke)
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      1. POPassing structure containing an array of structures between C and C# (DLL and P invoke)
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    1. COWhy are you packing? It's rather unusual for native structs to be packed.
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      1. USDavid Heffernan
    2. COThe packing is just for further use in my program :)
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    3. COI don't understand. If the native structs are not packed then your interop could very well fail.
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      1. POPassing structure containing an array of structures between C and C# (DLL and P invoke)
      1. USDavid Heffernan
 

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