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POCall a C++ DLL method from a C# application
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  1. POCall a C++ DLL method from a C# application
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    copied!<p>I'm trying to use a method from a C++ DLL in a C# project, but I'm, having problems calling it correctly. The method is this:</p> <p>As said in the SDK manual</p> <p><strike> DWORD WINAPI PrtRead (HANDLE hPrt, DWORD dwTimeout, DWORD *pdwType, LPDWORD pdwParArray, LPDWORD pdwArraySize, LPBYTE pbReadData, LPDWORD pdwReadDataLen) </strike></p> <p>As really defined on code</p> <pre><code>extern "C" __declspec(dllimport) DWORD PrtRead (HANDLE hPRT, DWORD dwTimeout, DWORD *pdwType, LPDWORD pdwParArray, LPDWORD pdwArraySize,LPBYTE pbReadData, LPDWORD pdwReadDataLen); </code></pre> <p>and in the SDK C++ sample they call it like this:</p> <pre><code>DWORD dwPar[2]; pdwParArray = &amp;dwPar[0]; dwPar[0] = 0; dwPar[1] = 0; DWORD dwRet = PrtRead(hPrinter, dwCurrentTimeout, &amp;dwType, pdwParArray, &amp;dwArraySize, NULL, &amp;dwReadDataLen); </code></pre> <p>My problem is getting the value LPDWORD pdwParArray.</p> <p>The DLL always returns one of the following values in position [0]: 1, 2 or 20 and in postion [1]: 1, 2 or 4, but I'm unbale to make it do this.</p> <p>I've tryed defining the import like this:</p> <pre><code>[DllImport("HPRDH.dll", CallingConvention = CallingConvention.Cdecl)] public static extern ulong PrtRead(IntPtr hPrt, ulong dwTimeout, ref ulong pdwType, XXXXXXXXX , ref ulong pdwArraySize, ref byte[] pbReadData, ref ulong pdwReadDataLen); </code></pre> <p>and varied XXXXXXXXX like this</p> <hr> <p>Method definition:</p> <pre><code>out ulong[] pdwParArray </code></pre> <p>Variable Initialization:</p> <pre><code>ulong[] pdwParArray; </code></pre> <p>Method returns:</p> <pre><code>pdwParArray = null </code></pre> <hr> <p>Method definition:</p> <pre><code>ref ulong[] pdwParArray </code></pre> <p>Variable Initialization:</p> <pre><code>ulong[] pdwParArray = new ulong[2]; pdwParArray[0] = 0; pdwParArray[1] = 0; </code></pre> <p>Method returns: pdwParArray[0] = 0; pdwParArray[1] = Out of bounds array index;</p> <hr> <p>Method definition: out ulong pdwParArray</p> <p>Variable Initialization: ulong[] pdwParArray = new ulong[2];</p> <p>Method returns: pdwParArray[0] = 0; pdwParArray[1] = 0;</p> <hr> <p>Method definition: ref ulong pdwParArray</p> <p>Variable Initialization: ulong[] pdwParArray = new ulong[2];</p> <p>Method returns: pdwParArray[0] = 0; pdwParArray[1] = 0;</p> <hr> <p>How should I define the LPDWORD pdwParArray in my C# import, how to initialize it and call it?</p> <p>Thanks in advance</p> <pre><code>_ _ _ _ </code></pre> <p><strong>EDIT:</strong> @TheMathemagician</p> <p>Tried the following with these results:</p> <p>Definition:</p> <p>[MarshalAs(UnManagedType.LPArray)] ulong[] pdwParArray</p> <p>Result:</p> <p>pdwParArray[0] = 0;</p> <p>pdwParArray[1] = 0;</p> <hr> <p>Definition:</p> <p>[MarshalAs(UnmanagedType.LPArray)] out ulong[] pdwParArray</p> <p>Result:</p> <p>pdwParArray[0] = null;</p> <p>pdwParArray[1] = null;</p> <hr> <p>Definition:</p> <p>[MarshalAs(UnmanagedType.LPArray)] ulong pdwParArray</p> <p>Result:</p> <p>Cannot marshal 'parameter #4': Invalid managed/unmanaged type combination (Int64/UInt64 must be paired with I8 or U8).</p> <hr> <p>Definition:</p> <p>[MarshalAs(UnmaDefinition:nagedType.LPArray)] out ulong pdwParArray</p> <p>Result:</p> <p>Cannot marshal 'parameter #4': Invalid managed/unmanaged type combination (Int64/UInt64 must be paired with I8 or U8).</p>
 

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