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POCalling a Delphi DLL from C# produces unexpected results
 

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  1. POCalling a Delphi DLL from C# produces unexpected results
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    <p>I have a Delphi DLL that I did not write, but need to call from a C# ASP.NET 3.5 app. Here is the function definition I got from the developers:</p> <pre><code>function CreateCode(SerialID : String; StartDateOfYear, YearOfStartDate, YearOfEndDate, DatePeriod : Word; CodeType,RecordNumber,StartHour,EndHour : Byte) : PChar; external 'CreateCodeDLL.dll'; </code></pre> <p>And here is my C# code:</p> <pre><code>[DllImport( "CreateCodeDLL.dll", CallingConvention = CallingConvention.StdCall, CharSet=CharSet.Ansi)] public static extern IntPtr CreateCode( string SerialID, UInt16 StartDateOfYear, UInt16 YearOfStartDate, UInt16 YearOfEndDate, UInt16 DatePeriod, Byte CodeType, Byte RecordNumber, Byte StartHour, Byte EndHour); </code></pre> <p>And finally, my call to this method: </p> <pre><code>//The Inputs String serialID = "92F00000B4FBE"; UInt16 StartDateOfYear = 20; UInt16 YearOfStartDate = 2009; UInt16 YearOfEndDate = 2009; UInt16 DatePeriod = 7; Byte CodeType = 1; Byte RecordNumber = 0; Byte StartHour = 15; Byte EndHour = 14; // The DLL call IntPtr codePtr = CodeGenerator.CreateCode(serialID, StartDateOfYear, YearOfStartDate, YearOfEndDate, DatePeriod, CodeType, RecordNumber, StartHour, EndHour); // Take the pointer and extract the code in a string String code = Marshal.PtrToStringAnsi(codePtr); </code></pre> <p>Every time I re-compile this exact code and run it, it returns a different value. The expected value is a 10-digit code comprised of numbers. The returned value is actually 12 digits. </p> <p>The last important piece of information is that I have a test .EXE that has a GUI that allows me to test the DLL. Every test using the .EXE returns the same 10-digit number (the expected result).</p> <p>So, I have to believe that I have declared my call to the DLL incorrectly. Thoughts?</p>
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