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POCannot p/invoke C method from C# due to marshalling issues
 

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  1. POCannot p/invoke C method from C# due to marshalling issues
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    <p>I'm trying to invoke the <code>I2CTransfer</code> function below, and immediately getting a <code>System.NotSupportedException</code>. I suspect my marshalling is wrong, but cannot work out the problem.</p> <hr> <p>Here are the C structures:</p> <pre><code>BOOL I2CTransfer(HANDLE hDev, PI2C_TRANSFER_BLOCK pI2CTransferBlock); typedef struct { I2C_PACKET *pI2CPackets; INT32 iNumPackets; } I2C_TRANSFER_BLOCK, *PI2C_TRANSFER_BLOCK; typedef struct { BYTE byAddr; BYTE byRW; PBYTE pbyBuf; WORD wLen; LPINT lpiResult; } I2C_PACKET, *PI2C_PACKET; </code></pre> <hr> <p>And here are the c# structures I'm attempting: </p> <pre><code>[DllImport("i2csdk.dll", EntryPoint = "I2CTransfer")] [return: MarshalAs(UnmanagedType.Bool)] public static extern bool I2CTransfer(IntPtr hI2C,ref I2C_TRANSFER_BLOCK pI2CTransferBlock); [StructLayout(LayoutKind.Sequential)] public struct I2C_TRANSFER_BLOCK { public I2C_PACKET[] pI2CPackets; public int iNumPackets; } [StructLayout(LayoutKind.Sequential)] public struct I2C_PACKET { public byte byAddr; public byte byRW; public byte[] pbyBuf; public UInt16 wLen; public IntPtr lpiResult; } </code></pre> <hr> <p>Calling code:</p> <pre><code>I2C_TRANSFER_BLOCK i2CTransferBlock = new I2C_TRANSFER_BLOCK(); I2C_PACKET packet = new I2C_PACKET(); int result; IntPtr resultPtr = IntPtr.Zero; //Populating data... byte[] pBuf = new byte[1 + pbData.Length]; pBuf[0] = (byte) ((regStart &amp; 0x7F) &lt;&lt; 1); Array.Copy(pbData, 0, pBuf, 1, pbData.Length); // Fill packet for register write packet.pbyBuf = pBuf; packet.wLen = (ushort) pBuf.Length; packet.byRW = NativeConstants.I2C_RW_WRITE; packet.byAddr = address; packet.lpiResult = resultPtr; // Fill transfer block i2CTransferBlock.pI2CPackets = new I2C_PACKET[] {packet}; i2CTransferBlock.iNumPackets = 1; // NotSupportedException here bool brc = I2CTransfer(port, ref i2CTransferBlock); </code></pre> <hr> <p>The arrays are initialized in C# before calling the method. </p> <p>I've tried adding <code>[MarshalAs(UnmanagedType.LPArray)]</code></p> <p>to the arrays (pI2cPackets, and pbyBuf) to no avail. </p> <p>This is on Windows CE - compact framework, .NET 3.5.</p> <p>Is there something obviously wrong with the above translation?</p> <p>Many thanks in advance. </p>
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    1. COplease, show the code, which you use to instantiate those structures and call the method.
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      1. USNikita B
    2. COYour username confused me there :) Done.
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    3. COThats what i do. I lurk around StackOverflow and steal people's names.
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      1. USNikita B
 

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