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POCall Win32 DLL from .NET with complex struct
 

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  1. POCall Win32 DLL from .NET with complex struct
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    <p>I have upgraded an old VB6 component to .NET. This component made a call to another Win32 component, with the following type structure:</p> <pre><code>Public Type DDPARAMS bAddressFlag As String * 1 bCompanyFlag As String * 1 bNameFlag As String * 1 bPremiseFlag As String * 1 ..etc </code></pre> <p>I cannot reference this Win32 DLL as it is not a COM DLL, so .NET can't create any interop for me automatically.</p> <p>I have the original source for the Win32 DLL (written in C), and the struct is defined here as:</p> <pre><code>typedef struct tagDDPARAMS { BYTE bAddressFlag; BYTE bCompanyFlag; BYTE bNameFlag; BYTE bPremiseFlag; BYTE sPremiseThreshold[3]; etc. </code></pre> <p>When I upgrade the VB6 component, the .NET code generated for the struct is:</p> <p>Public Structure DDPARAMS Public bAddressFlag() As Char </p> <pre><code> &lt;VBFixedString(1), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=1)&gt; Public bCompanyFlag() As Char &lt;VBFixedString(1), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=1)&gt; Public bNameFlag() As Char &lt;VBFixedString(1), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=1)&gt; Public bPremiseFlag() As Char &lt;VBFixedString(3), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=3)&gt; Public sPremiseThreshold() As Char &lt;VBFixedString(3), System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=3)&gt; Public sLooseThreshold() As Char </code></pre> <p>etc.</p> <p>However, when I run this code, I get the following error:</p> <p><strong><em>Type could not be marshaled because the length of an embedded array instance does not match the declared length in the layout.</em></strong></p> <p>I have googled and googled and am out of ideas - any help is appreciated.</p> <p>UPDATE: I tried the suggestion below and changed ByValArray to AnsiBStr (one byte string) and now get the following:</p> <p><strong><em>"Cannot marshal field 'sTown' of type 'DDRECORD': Invalid managed/unmanaged type combination (Arrays fields must be paired with ByValArray or SafeArray)."</em></strong></p> <p>Thanks a lot Duncan</p>
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