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copied!<p>To convert <code>PWideChar</code> to <code>AnsiString</code>:</p> <pre><code>function WideCharToAnsiString(P: PWideChar): AnsiString; begin Result := P; end; </code></pre> <p>The code converts from UTF-16, null-terminated PWideChar to <code>AnsiString</code>. If you are getting question marks in the output then either your input is not UTF-16, or it contains characters that cannot be encoded in your ANSI codepage.</p> <p>My guess is that what is actually happening is that your Delphi DLL was created with a pre-Unicode Delphi and so uses ANSI text. But now you are trying to link to it from a post-Unicode Delphi where <code>PChar</code> has a different meaning. I'm sure Rob explained this to you in your other question. So you can simply fix it by declaring your DLL import to return <code>PAnsiChar</code> rather than <code>PChar</code>. Like this:</p> <pre><code>function GetDeviceChannelInfo_HSI(PortNumber, Address, ChNumber: Integer; var State: Integer): PAnsiChar; stdcall; external DLL_FILENAME; </code></pre> <p>And when you have done this you can assign to a string variable in a similar vein as I describe above.</p> <p>What you need to absorb is that in older versions of Delphi, <code>PChar</code> is an alias for <code>PAnsiChar</code>. In modern Delphi it is an alias for <code>PWideChar</code>. That mismatch would explain everything that you report.</p> <hr> <p>It does occur to me that writing a Delphi wrapper to the DLL and communicating via stdout with your C# app is a very roundabout approach. I'd just p/invoke the DLL directly from the C# code. You seem to think that this is not possible, but it is quite simple.</p> <pre><code>[DllImport(@"mydll.dll")] static extern IntPtr GetDeviceChannelInfo_HSI( int PortNumber, int Address, int ChNumber, ref int State ); </code></pre> <p>Call the function like this:</p> <pre><code>IntPtr ptr = GetDeviceChannelInfo_HSI(Port, Addr, Channel, ref State); </code></pre> <p>If the function returns a UTF-16 string (which seems doubtful) then you can convert the <code>IntPtr</code> like this:</p> <pre><code>string str = Marshal.PtrToStringUni(ptr); </code></pre> <p>Or if it is actually an ANSI string which seems quite likely to me then you do it like this:</p> <pre><code>string str = Marshal.PtrToStringAnsi(ptr); </code></pre> <p>And then of course you'll want to call into your DLL to deallocate the string pointer that was returned to you, assuming it was allocated on the heap.</p>

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